Nano-engineered coatings and thin films: from design to applications

Resume : Transition-metal nitrides (MeN) and oxynitrides (MeNO) were significantly explored as candidates for numerous applications, including light harvesting, photoelectrochemical water splitting, refractory plasmonics, and gas sensing. In many cases, surfaces with highly developed micro- and nanostructures are required to enhance the efficiency of resultant devices. Diverse approaches were investigated to adapt reactive magnetron sputtering for the production of MeNO thin films with controllable architecture. Here, we report a sputter-based synthesis of MeN and MeNO nanoparticles (NPs) that can be collected on substrates in the form of mesoporous coatings providing high specific area. We take advantage of reactive magnetron sputtering of transition metals in Ar/N2 and use the configuration of a gas aggregation cluster source. The preferential formation of NPs instead of thin films is achieved because of a proper combination of gas pressure/flow and dc. The NPs are produced in the gas phase in the vicinity of the magnetron target and can be extracted by the gas flow for deposition on substrates. Examples of thus-produced mesoporous coatings include TaNO and HfNO NPs on Si. A general feature of the approach is that the structure, crystallinity, chemical, and optoelectronic properties of the NPs can be controlled by the gas-phase composition. However, fully stoichiometric MeN NPs are difficult to obtain: part of the metal valences remain unsaturated as discovered by in situ XPS. As revealed by DFT DoS calculations, such NPs consist of substoichiometric MeN with partially filled midgap states. The NPs partially oxidize when exposed to air, providing an inwardly directed gradient of the nitrogen concentration. The NPs exhibit plasmonic and photoluminescent properties in the visible range. In the case of TaNO, the annealing in ammonia with subsequent CVD of a FeNiOx cocatalyst produces photoanodes sensitive to solar light. Photoelectrochemical measurements detected the photocurrent reaching 2.5 mA/cm2 at 1.23 VRHE, while further optimization is also possible. Thus, this approach may offer a new route to advanced noble metal-free, MeNO-based optoelectronic devices. ACKNOWLEDGMENT: The work was supported by a GACR 21-12828S grant from the Czech Science Foundation.

Resume : During the last decade the mechanical properties and the oxidation resistance of high entropy nitride (HEN) thin films have been widely studied. Nevertheless, few information is available on other properties of this class of materials [1]. The objective of this work is to evaluate the physical properties of high entropy nitrides and to compare them to the properties of binary and ternary nitrides. (NbTaTiVZr)Nx films have been deposited by reactive co-sputtering of metallic targets. The chemical composition of the high entropy nitride films has been fixed by adjusting the current applied to the different targets. The nitrogen content measured by electron probe microanalysis has been tuned by the change of the nitrogen flow rate introduced into the chamber. The binary or ternary nitrides films have been deposited within the same process using the same deposition reactor. From X-ray diffraction analyses, the HEN films crystallize in a fcc structure with a preferred orientation along the [200] direction. To understand the quality of the structure, we used Raman spectroscopy (LabRAM Horiba with a HeNe laser excitation wavelength of 632.8 nm), which shows the presence of two implicit peaks of acoustic modes (longitudinal and transverse) in the region of 100-300 cm-1 and one peak of optical mode in the region of 500 cm-1 is probably associated with the point defects, according to the explanation from [2]. The film hardness has been measured using nanoindentation with a Berkovich tip. The films electrical resistivity has been measured at room temperature using a four point probe method. Depending on the film composition, the electrical resistivity is ranging between 100 and 1000 µW cm. Further information regarding the electrical properties (charge carrier density, electron mobility) have been obtained using Hall effect measurements. The results clearly show that HEN films exhibit better electrical properties than most of the binary or ternary nitrides. Optical characterization has been performed using UV-visible spectroscopy and photoluminescence. The obtained results evidence plasmonic properties for HEN films. [1] K. von Fieandt et al., Vacuum 193 (2021) 110517 [2] Hang Li et al., Journal of Alloys and Compounds 889 (2021), 161713

Resume : Amorphous CNx, Si-C-N, B-C-N and Si-B-C-N materials are studied by a combination of extensive ab-initio molecular-dynamics simulations (over 15 000 trajectories) in a wide range of compositions and densities with reactive magnetron sputtering in a wide range of sputter target compositions and discharge gas mixture compositions [1-3]. When and only when the amorphous structures are allowed to include unbonded N2 molecules, the predicted lowest-energy densities are in agreement with the experiment. The main attention is paid to the N2 formation, with the aim to predict and explain the relationships between [Si]/[B]/[C] ratios and the maximum achievable content of N bonded in stable amorphous networks ([N]network). The results reveal that N2-free networks are characterized by maximum [N]network between 34% (CNx) and 57% (SiNx). Networks formed in parallel to the formation of unbonded N2 molecules (which subsequently either diffuse out or stay trapped in the material) are characterized by maximum [N]network between 42% (CNx) and 57% (SiNx). The measured N contents in Si-(B)-C-N films prepared in our lab by reactive magnetron sputtering are in an excellent agreement with the prediction. Further analysis shows that while the N2 formation at a given total N content and in a wide range of [Si]/[B]/[C] ratios is given only by the packing factor, the lowest-energy packing factor depends on these ratios. The presented methodology constitutes a new way how to support the experiment by ab-initio simulations. The results are important for the design of amorphous nitrides for various technological applications, prediction of their stability, design of pathways for their preparation, and identification of what may or may not be achieved in this field. [1] J. Houska, Acta Mater. 174, 189-194 (2019), 10.1016/j.actamat.2019.05.048 [2] J. Houska, ACS Appl. Mater. Inter. 12, 41666-41673 (2020), 10.1021/acsami.0c08300 [3] J. Houska, Materials 14, 5744 (2021), 10.3390/ma14195744

Resume : High power impulse magnetron sputtering (HiPIMS) is a well-known physical vapor deposition (PVD) technique. HiPIMS process has low duty cycles, long off-time between pulses, very short voltage and high amplitude current pulse, which are applied to the target. This leads to enhanced ionization rate with beneficial consequences to produce high quality films with denser structure, smoother morphology and higher hardness compared to the conventional sputtering. In recent years, several studies were made using HiPIMS to deposit a range of metal nitride, metallic and metal oxide coatings onto rigid substrates. In this work, we focus on the study of alumina (Al2O3), which is a metal oxide and an electrical insulator with a limited number of works published using HiPIMS. This is due to arcing events caused by the formation of an isolating layer on the target, which creates instability during the reactive process. In this work, we successfully decrease it owing to the utilisation of a gas-feedback control, providing a stable discharge. Also, due to the wide range of diverse crystalline phases of alumina (α, γ, δ, η, χ, θ and k) it generates good properties such as good thermal stability, high hardness and transparency. Stoichiometric Al2O3 films were synthesized using HiPIMS and tuned to have different crystalline properties depending on the average power, duty cycle and the substrate temperature. These results will be compared with a more conventional technique such as DC mid-frequency and characterized by scanning electron microscopy, x-ray diffraction, AFM and nanoindentation. For an application standpoint, alumina can be used as a catalyst support given the physicochemical properties that change with the crystalline phase. Additionally, incorporating gold nanoparticles with alumina gives the ability to support localized surface plasmon resonance (LSPRs) creating plasmonic coatings. This permits to increase the catalytic activity by tunning the phase of alumina as well as the nanoparticle size and shape. For this reason, this plasmonic coatings will be electrochemically analysed in order to evaluate the catalytic activity. Keywords: Al2O3 matrix, Magnetron Sputtering, HiPIMS, pulsed mid-frequency, gold nanoparticles, plasmonic coatings

Resume : Mechanically flexible substrates for thin films are growing in popularity for electronic applications, such as for displays, printed circuit boards, as well as for advanced energy materials, for example, solar cells, batteries, and high temperature superconducting coated conductors (HTS). However, flexible substrates often do not have the surface smoothness required for optimized device performance and thus the low-cost advantages may not come to fruition. Several methods for planarizing, or levelling, the surfaces are possible. Among these are mechanical polishing, electropolishing, and chemical mechanical polishing. The current procedure involves gradual long steps of mechanical or electrochemical polishing showing high cycle times and intense manpower effort. In this work, we present the results of Solution-Deposition Planarization - SDP as a method to planarize Al2O3 flexible surfaces with Y2O3 inexpensively, eco-friendly in long lengths, and sustain high temperatures for further processing. At the beginning, the surface of the flexible Al2O3 tapes will be studied in order to quantify initial roughness and qualitative contribution of different types of expected defects such as rolling scratches, pores, grain boundary grooving. From the solution point of view, several parameters may affect the number of coatings needed to accomplish a certain level of planarization: concentration, type of solvents, metalorganic salts, presence of additives such as TEA, DEA or high-weight polymers. Thermogravimetric of the precursor solutions will be investigated in order to tune the thermal treatments for each coating. It is also relevant to enhance the rheological properties (viscosity, surface tension) and surface wettability (contact angle) of the precursor solutions in view of accomplishing a correct initial liquid coverage and avoiding dewetting process during subsequent manipulation. Regarding the methodology for depositing the liquid layers, dip-coating is thought to be convenient for studying the different aspects of the layer multideposition in long lengths, typically less than 5-10 cm. The obtained samples are then analyzed via AFM and XRD for characterization. We show that Solution-Deposition Planarization - SDP can produce surface roughnesses less than 3-5 nm rms on as small scale 5x5μm2, when starting with surfaces 50 times rougher. Using this template, the deposition of YBCO thin films, is carried out via standard low-fluorine MOD route and pulsed laser deposition (PLD). The obtained films are analyzed via SEM, XRD, VSM, DC resistivity and critical current measurements. Acknowledgements This work was supported by UEFISCDI through PN-III-TE SUPRA-FLEX research grant No. 191/2021.

Resume : Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are versatile building blocks in a large range of biomedical and environmental applications due to their good magnetic performance, ease of production, and low toxicity. To be used in these applications, SPIONs must be functionalized to possess sufficient chemical and colloidal stabilities and to allow their post-functionalization using (bio)molecules. SPIONs are often functionalized with organic ligands bearing chelating groups such as amines, phosphates, hydroxyls, and carboxylates. The anchoring of the chelate-type group is influenced by the pH and the ionic strength. Hence, developing an efficient chemical functionalization strategy to obtain a robust and stable linkage between the organic coating and the SPION surface remains challenging; particularly when this layer serves as a platform to conjugate (bio)molecules such as drugs and/or targeting agents. An interesting novel strategy to enhance the SPIONs stability takes advantage of the properties of calix[4]arene-tetra-diazonium compounds, which has been proven to be successful with metallic nanomaterials, providing them with extreme chemical and colloidal stabilities, while allowing their further conjugation with a defined density of (bio)molecules.1 Here, we have extended this approach to 16 nm SPIONs composed of maghemite (γ-Fe2O3) synthesized by the co-precipitation of iron chlorides in basic medium followed by oxidation to Fe(III) by acid treatment. The as-prepared SPIONs were functionalized with a thin organic layer of the calix[4]arene-tetra-acid-tetra-diazonium salt in basic conditions. TEM characterization of both samples revealed almost identical particle size distributions with interplanar distances associated with the inverse spinel structure of γ-Fe2O3. The composition of the organic layer was confirmed by IR spectroscopy. Hysteresis loops at room temperature for both samples showed no remanence and high saturation magnetization, which are typical features of high crystallinity SPIONs. In addition, calix-SPIONs showed enhanced stability under magnetic separation, pH, and high salt concentrations compared to the same particles functionalized with sodium citrate or with the aryl diazonium salt. This was probably due to the more robust anchoring of the organic coating induced by the possibility to form multiple bonds with the surface thanks to the macrocyclic structure of the calixarenes. Finally, a post-functionalization step of the calix-layer was demonstrated with polyethyleneimine (PEI), which has recently attracted the attention for the functionalization of SPIONs due to the potential of these nanohybrids in both health and environmental applications such as DNA Delivery Systems, contrast agents for cancer diagnosis, or for the selective extraction of metals from industrial effluents. We plan to extend this strategy using other calixarenes bearing useful functional groups, and mixtures of them, paving the way to robustly protected SPIONs with well-defined numbers of functional or postfunctionalizable groups. 1 M. A., Lenne Q., C. Padilha J., Troian-Gautier L., Leroux Y.R., Jabin I. and Lagrost C. (2020) Strategies for the Formation of Monolayers From Diazonium Salts: Unconventional Grafting Media, Unconventional Building Blocks. Front. Chem. 8:559. Doi: 10.3389/fchem.2020.00559

Resume : Nanostructured surfaces produced by thermal nanoimprinting lithography of polymers such as polymethyl methacrylate (PMMA) have properties interesting for many different applications. However, the mechanical durability and thermal stability of such surfaces is limited. Inorganic thin films can improve the surface robustness as well as change its physicochemical properties. In this contribution, we demonstrate the use of thin TiO2 film to protect and increase wear and temperature resistance of moth-eye nanostructures fabricated in PMMA. By coating the surface with a thin oxide film deposited by magnetron sputtering, the temperature stability was increased from 100°C to over 250°C, well above the glass transition temperature of the PMMA matrix. The moth-eye nanostructures consist of subwavelength arrays of tapered cones that act as a graded refractive index surface with omnidirectional antireflection. The nanostructures were fabricated by thermal nanoimprinting in PMMA and then coated by reactive magnetron sputtering with TiO2 films 50 and 100 nm thick. Nanoscratch tests showed that plastic deformation was prevented up to 1 mN while also decreasing the scratch depth. Grazing-Incidence Small-Angle X-ray Scattering during annealing demonstrated that the coated structures were preserved during the thermal annealing process in contrast to the uncoated surfaces. Additionally, the initially amorphous TiO2 turned crystalline upon annealing and this resulted in additional photoinduced superhydrophilicity upon UV light irradiation and self-cleaning behaviour.

Resume : Polar-oxides provide unique challenges for atomic control at their surface due to the repeating dipole moment that increases the surface potential for each unitary layer within the structure, even in the case of thin-films. A consequence of this “polar-catastrophe” is large scale reconstructions of the surface geometry. First-principles modeling of the growth dynamics of polar MgO(111) films reveal that the process does not proceed layer-by-layer. Instead, the Mg or O layers grow up to a critical sub-monolayer coverage, beyond which the formation of a new layer, of the other species, becomes energetically favourable over completion of the current layer. This non-layer-by-layer growth is accompanied by complex relaxations of atoms both at the surface and in the sub-surface and is triggered by the polarity of the thin-film as shown by neutral growth directions exhibiting Frank–Van der Merwe growth. The incomplete layers in the growth of the thin-film polar oxides lend themselves naturally to surface faceting. Following from this, Thin-films of MgO(111) and NiO(111), grown via molecular beam epitaxy and studied via transmission electron microscopy, demonstrate that the surface stabilization is achieved through the formation of neutral {100} nano-faceted surfaces. These facets are limited in size by an asymptotical surface energy relation to their height; with the reconstruction being more stable than previously reported theoretical surface terminations across a wide range of growth conditions. The termination offers access to lower coordinated atoms at the intersection of the neutral {100} planes whilst also increasing the surface area of the film. The unique electronic structures of these surfaces can be utilized in catalysis, as well as for forming unique heterostructures for electronic and spintronic applications.

Resume : Copper oxide is used in chemical reactions as a catalyst or catalyst precursor in presence of hydrogen as a reactant or a product. Controlled reduction process with known reduction kinetics of well-defined Cu-oxides in hydrogen is a key issue for the activation of oxide catalysts as well as for other technological fields such as gas sensing and nanopaste sintering. For practical and technological reasons, the reduction kinetics of CuO and/or Cu2O reduction process in H2 and/or CO gas mixtures have been mostly studied on (sub)micron-sized powder mixtures, pressed pellets and nanoaggregates with broad and unspecified size and shape distribution. In this study, we have prepared dense polycrystalline single-phase Cu2O and CuO films with different thicknesses (ranging from 80 to 500 nm) by controlled thermal oxidation of Cu sputter-grown thin films [1]. The Cu2O and CuO films were reduced at ~300 °C in H2 atmosphere (%5 H2 in Ar), while monitoring the incubation time, the phase transformation sequence and associated reduction kinetics by in-situ time-resolved synchrotron X-ray diffraction. The combination of a high intensity of synchrotron radiation with a custom-designed furnace with full atmospheric control makes it possible to conduct sub-minute, time-resolved XRD measurements under a wide variety of temperatures and atmospheric conditions. In addition, the grain sizes and strain states of the developing CuO, Cu2O and/or Cu phases during the reduction process have been resolved in detail for the first time. Highly nanoporous Cu, CuO and Cu2O structures are obtained by alternating oxidation and reduction steps at specific conditions from an initially dense and smooth Cu thin films, which can be envisaged for a wealth of applications in the fields of catalysis, batteries, water treatment and biomedical applications. [1] Y. Unutulmazsoy, C. Cancellieri, M. Chiodi, S. Siol, L. Lin, L.P.H. Jeurgens, Journal of Applied Physics, 127 (2020) 065101. 10.1063/1.5131516.

Resume : Adapting existing nanomanufacturing methods to emerging forms of large-area electronics presents numerous technological and economic challenges. Despite the difficulties, however, a plethora of new devices have been gaining ground, transforming the broader marketplace and relevant manufacturing infrastructure. In this talk I will discuss our recent work towards scalable nanomanufacturing of emerging forms of large-area electronics. I will show how the development of innovative patterning technologies in tandem with advanced functional materials, can pave the way to sustainable large-area electronics with unprecedented performance characteristics. Particular emphasis will be placed on the development and evolution of adhesion lithography (a-Lith) and its use in an expanding range of applications ranging from ultra-fast opto-electronics to new forms of reactors for solar fuels generation.

Resume : α-quartz is an important material for microelectronic industry since it is selected to fabricate the oscillators and transducers present in any electronic device. However, to-date α-quartz applied to microelectronics is exclusively synthetized by hydrothermal methods, which produce big crystals making impossible to decrease their size and for most applications these crystals need to be bonded on Si substrates. This feature represents an important barrier for the microelectronics industry since thinner monocrystalline quartz plates are currently highly demanded for faster device operation, higher frequency filtering or to produce transducers with lower detection levels and improved sensitivity. In the present work, we report the fabrication of the first epitaxial piezoelectric nanostructured (100)α-quartz/(100) Si-based cantilever due to the combination of chemical solution depostion, soft-nanoimprint lithography and top-down microfabrication processes. By using SOI technology, we are able to modify the dimensions and designs of quartz-based cantilevers while preserving a coherent (100)quartz/(100)silicon crystalline interface and piezoelectric properties [1,2]. We have engineered piezoelectric cantilevers exhibited a dimension of 40 µm large and 100 µm long with with a 600 nm thick patterned quartz layer epitaxially grown on a 2 µm thick Si device layer. We measured a resonance frequency at 267 kHz (comparable to similar commercial tip less cantilevers) and the estimated quality factor Q of the whole mechanical structure is Q = 398 under low vacuum conditions. Importantly, we obtained a sensitivity of 1 µN.Hz-1 which results in a mass detection sensitivity of 100 ng Hz-1, using an atomic force microscope. Because quartz-based devices are highly used for chemical and biosensing applications, such as quartz crystal-microbalance-based setups, we determined the biocompatibility of nanostructured α-quartz devices engineered by chemical solution deposition. We confirmed that human epithelial cells, such as HT1080 cells, adhere and can be cultured on patterned epitaxial α-quartz thin films. Moreover, we found that nanostructured α-quartz thin films can induce the self-organization of the epidermal growth factor receptor (EGFR) on cellular membrane. As a result, nanostructured biocompatible piezoelectric quartz-based MEMS could be applied for biosensing applications in the near future. [1] Claire Jolly et al. Soft chemistry assisted On-chip Integration of Nanostructured quartz-based Piezoelectric Microelectromechanical System. Adv. Mater. Technol. 2021, 6, 2000831. [2] Claire Jolly et al. Epitaxial Nanostructured α-Quartz Films on Silicon: From the Material to New Devices. J. Vis. Exp;(164), e61766, doi:10.3791/61766 (2020).

Resume : The possibility to control various parameters of light, such as the polarization, the phase, or the intensity broadens the scope of research tools, especially in fields, where complexly structured optical fields are requested. Industrial applications benefit also as tools used in machining, welding or other desirable processes become complexly engineered. Experimentally the control of electromagnetic fields is realized using computer-generated holograms, spatial light modulators, and various types of metasurfaces or other advanced kinds of optical elements. Here, one of the promising approaches is the so-called geometric phase (GF) based elements. These diffractive elements are compact and capable of emulating classical optical elements or performing even better. This is ensured by locally altering the angle of the nano-grating which corresponds to a single pixel in the plane of the optical element. This angle is related to the Pancharatnam-Barry phase or, in other words, to the geometric phase. This technology is realized by inscribing nanogratings using a high-power femtosecond laser system. The retardance and the geometrical phase are controlled by the inscribing laser beam. One of the exciting optical fields are Airy beams, they are well known for their diffraction-free intensity profile and for the curved (parabolically accelerating) structure in the direction of the propagation. When interacting with obstacles, Airy wave packets also exhibit self-healing properties. This type of robustness is very useful in turbulent environments. In this work, we propose an Airy beam with a nonhomogenous polarization structure. A classical method is used to construct optical fields, from the Airy beam, that correspond to the two orthogonal modes ? electric and magnetic fields. The intensity profile of the resulting beam is altered by the singularities ? point and line like, these singularities correspond to the choice of polarization. Further, a Fourier spectrum is calculated and used to design an optical GF element using laser inscribed nanogratings. Fabrication of the element is discussed and verified.

Resume : Copper (Cu) is an attractive conductor for electronics thanks to its electrical and thermal properties and its relatively low price. However, Cu is susceptible to continuous oxidation which compromises those advantageous properties. This poster shows how an ultra-thin over-layer of samarium (Sm), equivalent to a metal thickness of 2-3 atoms, deposited by simple thermal evaporation is remarkably effective at passivating evaporated polycrystalline Cu films towards oxidation in ambient air: The stability of 9 nm Cu films is increased by an order of magnitude[Figure 1a]. Not only does the Sm overlayer passivate the 9 nm Cu film, but it also lowers the work function of the electrode to ca. 3.8 eV. The combination of low work function, high stability in ambient air and high reflectivity makes this electrode attractive for application as the reflective cathode in ITO-free top-illuminated organic photovoltaic devices (OPV). The results of a combined X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), atomic force microscopy and grazing-incidence small-angle X-ray scattering study of this system are presented [Figure 1b] together with preliminary OPV device studies.

Resume : Π-conjugated polymers have high charge carrier transport properties along their main chain which is a primary factor affecting the electrical behaviour of Organic Field Effect Transistor (OFETs) devices fabricated from these materials. There have been reports of diketopyrrolopyrrole-based (DPP) polymer nano wires showing promising OFET behaviour. However, so far there has been little control over the uniformity, orientation and alignment of these nano structures. Herein, we report a solution-coating procedure to fabricate micro and nano wires from a DPP-based polymer utilizing the shear coating method. A detailed study of the deposition conditions for the polymer produced aligned polymer wires that are along the coating direction, whose sizes range from mm to nm. We also show that there are several morphological regimes—film, intermediate, wires. Furthermore, the as-fabricated wires are isolated, i.e. free of any surrounding thin film phase, which we confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. Beside the macroscopic alignment of the wires, polarised optical microscope shows high birefringence suggesting a high degree of molecular orientation within the wires. This hypothesis is validated by the improved electrical characteristics of the individual-wire OFETs. The above results reveal an interesting arena for research on OFETs elucidating the benefits of bad solvents and pre-aggregation of π-conjugated polymers towards better controlled, isolated and highly aligned devices by using the optimized shear coating conditions.

Resume : Motor disabilities are one of the most serious diseases affecting the elderly, resulting in a burden for the day societies, with large monetary and social costs. The work presented here, aims to contribute to the World Health Organization (WHO) Global Strategy and Plan of Action for Healthy Aging and was dedicated to functionalizing specific areas of clothing to provide them with the ability to monitor the electrical activity of muscles (EMG) and simultaneously send electrical stimuli, building a new rehabilitation paradigm. Integrated into a garment, a novel system of sensors will be used to rehabilitate advanced muscle injuries and/or lack of mobility, especially in the elderly by using electrical stimulation based on the diagnosis of neuromuscular activity. For this purpose, a high-performance system of dry and flexible (nano)sensors based on Ti thin films with custom nanostructures has been prepared using the clothing itself as substrates. In order to optimize the mechanical and electrical response of these special clothes, the thin films were doped with different amounts of copper, giving rise to different compositions and morphologies. The adhesion of the films on the different knits, used for the production of the garment, was tested and improved using different physical plasma treatments, responsible for increasing both the surface free energy and the surface roughness. In addition, Ti-Cu thin films have shown the ability to develop structural features typical of Thin Film Metallic Glasses (TFMG), which in the end were able to withstand higher mechanical deformations with no significant changes in the electrical conductivity. Eletromechanical tests conducted in all the knits revealed very promising results, as low and moderated deformations were able to improve the electrical response of the sensor.

Resume : Oxygen plays a key role in the energy-generating processes of living entities, thus being one of the most important element for life, fundamental in liquid as well as in gaseous environment. In culture media for example, dissolved oxygen level is an interesting parameter worth monitoring because in hypoxic conditions cells grow faster and live longer. On the other hand, oxygen gas deficiency still represents a major threat for workers in confined spaces, since injuries or death caused by reduced oxygen levels are more frequent than for other hazardous gases. In this work, the electrocatalytic activity of the semiconducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) towards oxygen was exploited to transduce the oxygen concentration into a variation of the polymer conductivity. Indeed, PEDOT:PSS switches from the less conductive neutral state to the more conductive oxidized one, upon oxygen-concentration increase, according to the following equation: 4Pedot^0+O_2+4H^+ → 4〖Pedot〗^++2H_2 O We used Organic Electrochemical Transistors (OECTs), having both channel and gate made in PEDOT:PSS, for O2 sensing, measuring the current variation in the channel caused by different oxygen percentage: the transistor configuration carried signal amplification, excellent sensitivities and filtering of raw signal. Dissolved oxygen sensing was performed both in standard saline solution and in culture media, in the selected range [0-5% (v/v)] of O2. The extremely low limit of detection in the biological environment (3 μM, equivalent to an oxygen percentage amount of 0.25%) allows to foresee potential investigation of in-vitro cultures grown in hypoxic conditions. Oxygen gas sensing was obtained by sobstituting the liquid electrolyte with an agarose-based thin hydrogel film (30μm): the fast O2 solubilization in the hydrogel enabled the real-time oxygen monitoring in a concentration range that is significant for work-safety applications [13-21% (v/v)]. The low-power consumption (30 - 40 µW) and bendability (without loosing performances) of the devices patterned on flexible, 125 µm thick Polyethylene napthalate (PEN) films, paved the way for a final sensors that could be integrated in worker overalls as a standard protective equipment.

Resume : In the world of nanotechnology, where only a slight change in composition can significantly alter the physical and chemical properties of the product, optimal alloying is of utmost importance to fabricate nanoparticles with desired characteristics. Additionally, nanoparticles of nominally the same composition often exhibit a high degree of individuality in their morphology, which translates into a need for vast amounts of data for statistically relevant structure-function correlations. Combining these two aspects with also varying the size and shape of the nanoparticles, if a new sample would have to be made each time, any systematic search for optimal parameters for a desired application will take on unmanageable proportions. As a solution to this problem, we have developed a microshutter device that can be used in combination with physical vapor deposition (PVD) to grow metal thin films with precise thickness and position control that enables establishing compositional gradients across the sample. Combined with a nanolitography step, this method thus allows for precise fabrication of nanoparticles with different compositions and sizes on the same sample, with spatial control down to the level of the individual nanoparticle. In its practical implementation, we use a piezoelectric actuator in the PVD system to move a 116 x 5000 µm aperture in a silicon nitride membrane across the sample to define both the specific area for material deposition, as well as the total amount (thickness) of material deposited in this area. In this way, by subsequently evaporating multiple layers of different metals with tailored thickness and subsequent thermal annealing of the sample, alloy nanoparticles of locally well-defined composition can be produced [1]. To demonstrate the capability of the microshutter, we have nanofabricated arrays of PdAu alloy nanoparticles with gradually increasing contents of Au controlled at the level of the individual particles in the array and with 2 % composition resolution, as confirmed by EDS analysis. Finally, we have applied single particle plasmonic nanospectroscopy and imaging techniques ([2,3]) to demonstrate the thermodynamic and kinetic response of the nanoparticles to hydrogen as a function of composition, motivated by their application in state-of-the-art plasmonic hydrogen sensors [4]. 1. Nugroho FAA, et al. Bottom-Up Nanofabrication of Supported Noble Metal Alloy Nanoparticle Arrays for Plasmonics. ACS Nano 2016, 10(2): 2871-2879. 2. Syrenova S, et al. Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape. Nature Materials 2015, 14: 1236–1244 3. Albinsson D, et al. Copper catalysis at operando conditions—bridging the gap between single nanoparticle probing and catalyst-bed-averaging. Nature Communications 2020, 11(1): 4832. 4. Nugroho FAA, et al. Metal–polymer hybrid nanomaterials for plasmonic ultrafast hydrogen detection. Nature Materials 2019, 18(5): 489-495.

Resume : This work presents room temperature operable NO2 gas sensors fabricated from vertical few-layered 3D-MoSe2 porous nanowall thin films prepared by a scalable sputtering technique at room temperature without any post-annealing and selenization treatment. The microstructural and compositional studies were carried out using XRD, Raman, FESEM, HRTEM, EDS and XPS to identify the quality and properties of the deposited MoSe2 thin films and to realize the underlying gas sensing mechanism. The NO2 gas sensing performance of vertically aligned MoSe2 porous nanowall thin film sensors was recorded over a wide range of NO2 gas concentrations (0.1 to 50 ppm) at room temperature (30 °C). The fabricated sensing device based on grown MoSe2 thin film exhibits excellent sensing performances (sensor response = –78.3% and response/ recovery time ~ 20 s/ 174 s for 10 ppm NO2 gas) along with high selectivity and adequate stability at room temperature. The observed substantial enhancement in sensing performance is attributed to the superior charge transfer process as a consequence of augmented adsorption of gas molecules mediated by the higher surface-to-volume ratio of the unique nanostructure, i.e., edge-enriched crystalline MoSe2 nanowalls along with the 3D porous surface structure in addition to the significant catalytic activity of MoSe2. Thus, this uniquely developed highly nanocrystalline sputtered MoSe2 porous nanowall thin films with vertically aligned molecular layers deposited at room temperature is cost-effective and highly desirable for developing low-powered high-performance gas sensors.

Resume : Noble-metal ultrathin films, with nominal thickness smaller than ~15 nm, are ubiquitous in a wide range of plasmonic devices and other optoelectronic applications. Silver (Ag) layers have recently gained interest as alternative transparent conductive electrode (TCE) candidates for flexible photovoltaics to currently used indium tin oxide, which is inherently brittle and suffers from high cost and poor sustainability. However, Ag films obtained by conventional physical vapor deposition have the natural tendency to self-assemble into 3D agglomerates on weakly interacting substrates, resulting in the formation of rough surface profiles. Therefore, strategies to produce fully continuous, ultrathin and ultrasmooth Ag layers without compromising their electrical conductivity are needed. Among them, the use of gaseous additives, such as N2 or O2, appears as an efficient route to shift the continuous film formation thickness to lower values [1,2]. However, to understand the full evolutionary growth regime requires the implementation of in situ and real-time diagnostics. In the present work, the impact of N2 addition on the morphological and structural evolutions of ultrathin Ag layers is investigated by coupling complementary in situ and real-time diagnostics. Lab-scale studies include wafer curvature, surface differential reflectance spectroscopy and electrical resistivity to determine the morphological transition thicknesses (percolation and continuous formation thickness) [3] as a function of N2 partial pressure. These are augmented by real-time X-ray synchrotron studies (SIXS beamline at SOLEIL) in which the diffraction and reflectivity signals are simultaneously recorded, together with stress evolution. This enable us to explore the influence of N2 on island shape, texture and stress development, as well as relaxation mechanisms during growth interruptions. 1. Yun, J. et al. An unexpected surfactant role of immiscible nitrogen in the structural development of silver nanoparticles: An experimental and numerical investigation. Nanoscale12, 1749–1758 (2020). 2. Jamnig, A. et al. 3D-to-2D Morphology Manipulation of Sputter-Deposited Nanoscale Silver Films on Weakly Interacting Substrates via Selective Nitrogen Deployment for Multifunctional Metal Contacts. ACS Appl. Nano Mater.3, 4728–4738 (2020) 3. Colin, J. et al. In situ and real-time nanoscale monitoring of ultra-thin metal film growth using optical and electrical diagnostic tools. Nanomaterials10, 2225 (2020)

Resume : Recent developments in advanced coatings and coating processes allow for the production of functional coatings of great quality. However, now more than ever, environmental accountability of these processes should stay one of the priorities. At the same time, the economics of the processes must be assessed in order to keep them profitable. In this work, a novel way of assessing jointly the environmental impact as well as the costs of a process will be presented. To illustrate that method, a case study involving titanium aluminum nitride (TiAlN) coatings for machining applications deposited by both Direct Current Magnetron Sputtering (DC-MS) and Hi-Powered Impulse Magnetron Sputtering (HiPIMS) is described. The costs of both technologies will be assessed using Techno-Economic Analysis (TEA) as well as the CO2 emissions along all the life cycle of the coatings: extraction of materials, deposition processes, and machining phase. With the joint us of the two assessment methods, it can be shown that, while the coating process itself is more costly as well as generating more CO2 for HiPIMS (around 41% increase in cost and 68% increase in CO2 emissions), the lifetime of a tools coated by HIPIMS is longer by around 50% compared to DC-MS. This leads to a justifiable cost for the HiPIMS technology. Furthermore, when the machining phase is included in the analysis, it can be shown that, thanks to the longer lifetime of HiPIMS coatings, using HiPIMS technology can actually be even more advantageous than DC-MS as the longer lifetime leads to a lower usage of substrates in addition to a lower amount of downtimes in the machining phase. It can therefore be shown that the final outcome is in favor of HiPIMS by around 10% in terms of costs and by around 16% in terms of emissions of CO2. In addition to an analysis of that base case, several scenarios are also presented and discussed. These scenarios involve different cutting speeds in the machining phase as well as different scenarios for the lubrication.

Resume : Nano-multilayers (NMLs) are functional nano-architectures, which physical properties can be tailored by smart microstructural and interfacial design. Upon thermal treatment, the layered structure of NMLs of immiscible metals degrades, forming the nanocomposite (NC) microstructure. The driving force of the degradation is of capillary nature, i.e. the system tends to decrease the energies of interfaces by wetting. In the present work, the degradation upon thermal annealing (400 – 800 °C; duration of 100 min) of sputtered Cu/W NMLs with different nanolayer thicknesses (3, 5, 10 nm) is rationalized. It was revealed that the transition to NC starts only when the major part of initial residual stresses (–0.5 ÷ –3.0 GPa for Cu; –3.0 ÷ –7.0 GPa for W) is released. It can be attributed to the large magnitude of interface stress f, which is defined as the work necessary to strain Cu/W interfaces (strong Cu{111}<–101>||W{110}<–111> texture presents in all NMLs): the calculated value is 11.25 ± 0.56 J/m2. The interface stress increases the work required to create the unit of strained Cu/W interface. It was found that the magnitude of interface stress f decreases to zero at the temperatures of the onset of NML degradation (700 – 800 °C), and the f(T) dependence is the linear function. Thus, the required work decreases, what can promote the complete wetting of certain W/W grain boundaries, i.e. grain boundary wetting is related to the stress levels in Cu and W nanolayers.

Resume : Nanostructured W-Mo thin films were elaborated using DC magnetron co-sputtering related to Glancing Angle Deposition (GLAD). Two targets of tungsten and Molybdenum were used with an oblique angle around 80° between its normal and the normal to the substrate. These two metals are miscible between them and have practically the same self-diffusion energy which could be a critical point for the Janus structure creation. Different samples were prepared using the same tungsten target current of 140 mA and a variable molybdenum target current that increases from 10 mA to 200 mA. Several analyses were carried out such as SEM and XRD to study the structure of the thin films, their morphology, elemental composition and microstructure. W-Mo thin films exhibit a Janus-like structure with a clear separation between W and Mo, repeated withal columns. A checkboard-like structure has also been obtained after rotating the silicon substrate by 180°. The electrical resistivity was measured using Van de Pauw method and is also influenced by the target intensity, the resistivity and anisotropy values being correlated with the morphology of the thin films.

Resume : Interaction of He ions or helium plasmas with materials has been widely studied, especially in the frame of researches on nuclear fusion. It has been proved that due to its low solubility and high mobility in metals, Helium is able to diffuse on a long pathway, inducing the formation of vacancies where it can accumulate. This finally may lead to the formation of He filled high pressure nanosized bubbles, which presence inside the material drastically modify the properties. When helium is incorporated and trapped at the very near surface, it has been shown that rupture of the metal lattice can occur which induces processes like flaking or the interstitials emitted by trap mutation during the formation of the bubbles can lead to the so-called porous fuzz structure]. The objective of the present work is to study the deposition of thin films by DC magnetron sputtering in Ar/He atmospheres in order to benefit from this particular behavior of helium. In that aim we coupled simulation of the sputtering, transport and growth processes (using SRIM, home-made software and molecular dynamics) with gas phase analysis (mass spectrometry, plasma diagnostic) and thin film characterization. Film micro- and nano-structure was analysed by scanning and transmission electron microscopies. X-ray diffraction was employed to study the crystalline quality. Helium content was measured by proton elastic backscattering spectroscopy. In an attempt to qualify the nature of the vacancy defects, positron annihilation spectroscopy was conducted. We investigated the sputtering of Si, Al and Zr in helium containing atmospheres. We evidenced that, depending on the He proportion in the gas phase and on the element, films of different nature can be elaborated. For instance, gas/solid nanocomposite films where He is trapped in pores dispersed over the entire thickness or highly porous nanostructured films were obtained. All these films exhibit completely different properties than that usually deposited in Ar gas. Our results allow to give some insight into the mechanisms and species responsible for the formation of such different films. We investigated how adding He in the gas phase induces the change of the plasma regime which affects the sputtering of the atoms at the target, but also their transport to the substrate. Since turning from Ar to He drastically modifies the probability and efficiency of sputtered atoms/gas atoms collisions, the energy distribution functions of the particles impacting the growing film are greatly affected. Moreover, the role of the high energy He ions backscattered and neutralized at the target and then transported to the substrate is suspected to be significant. This will be discussed in this contribution. In the case of aluminium, the fiber-like highly porous obtained structure will be tested on hydrogen production by hydrothermal route.

Resume : Pt nanoparticles (NPs) are widely used as catalysts for oxygen reduction reactions (ORR) in electrochemical systems as the Proton Exchange Membrane Fuel Cell (PEMFC). NPs can be obtained through various physical, chemical or physicochemical routes. The chemical methods are very versatile in terms of controlling NPs shape and size but requires additives, which generate by-products difficult to remove and NPs with limited purity. In contrast, physical methods as magnetron sputtering on solid substrates avoid the use of additives, allowing the production of pure metallic NPs. In order to make the magnetron sputtering process compatible with conventional liquid ink preparation techniques used for manufacturing fuel cell, we recently reported the synthesis of Pt NPs over a host liquid substrate (glycerol) that sustains low pressures [1]. Vulcan XC72 and biosourced carbon NPs (produced from glucose) were added to the NPs colloidal solution in order to obtain Pt/C ink. This mixture was filtered, washed and dried in order to obtain dried Pt/C ink ready to be used for ORR. Molecular dynamic simulations highlighted that the NPs diffusion in the liquid phase depends on the associated kinetic energy of Pt atoms when arriving on the liquid surface and thereby depends on the plasma / liquid interaction properties. In this study, we investigated these interactions and the gas phase properties using experimental techniques as (an energy resolved) mass spectrometer and energy flux probe giving us access to the energy distribution of the sputtered species, total energy influx incoming onto the liquid and the gas phase composition. These results are correlated to the NPs physical properties obtained by X Ray Diffraction/Diffusion and High Resolution Transmission Electron Microscopy, enabling us a better understanding of the Pt NPs growth phenomena on and in the liquid phase. Keywords: plasma sputtering, nanoparticles, plasma – liquid interactions. References: 1. Orozco-Montes, V. Caillard, A., Brault, P., Chamorro-coral, W., Bigarre J., Sauldubois, A., Andreazza, P., Cuynet, S.,Baranton, S., Coutanceau, C (2021), Synthesis of Platinum Nanoparticles by Plasma Sputtering onto Glycerol: Effect of Argon Pressure on Their Physicochemical Properties, J. Phys. Chem. C, 125, 5, 3169–3179.

Resume : As we will proceed to move away from fossil fuels, an environmentally friendly, and industrial relevant fabrication of sustainable electronic devices is as topical than ever. Spray deposition is a fast and easy-to-implement technique, and already highly used in the industry to deposit thin, homogeneous films on a large scale. Functional nanocomposites are of high interest, as they combine favorable properties of different materials in a hybrid material. Here, we explore spray deposition to fabricate two types of thin (200 nm), and transparent nanocomposite electrodes consisting of wood-based, lightweight, and flexible cellulose nanofibrils (CNFs) as sustainable matrix material and highly conductive silver nanowires (AgNWs). Type I is a layered structure of an AgNW network sprayed on top of a thin CNF layer, while type II consists of a mixed layer of CNF and AgNW. We correlate the structural, morphological and electrical properties of both types using UV-Vis, SEM, AFM, grazing incidence small angle X-ray scattering (GISAXS), and four-point conductivity measurements. Our results demonstrate that the mixed type II has a lower roughness, allows for earlier onset of conductivity and shows a lower sheet resistance than type I. Hence, the addition of CNFs to the AgNWs-solution upon spraying has beneficial templating effects on the electronic properties of the resulting AgNW network.

Resume : The deposition rate and properties of MLD films are for a large part determined by what happens during the precursor exposure step. In some cases, however, the purge step is of equal importance, for example in the MLD of alucone films using trimethylaluminum (TMA) and ethylene glycol (EG). These alucone films tend to be porous in nature due to which the reactants during their exposure step not only react at the film surface but also tend to infiltrate into the film. The outgassing of the infiltrated reactant can take relatively very long thereby becoming the deposition rate-limiting step. If enough purge time is not provided for the reactant to outgas, it will lead to an additional CVD component alongside MLD in the overall growth. We have investigated the MLD of alucone focusing on the effect of purge time of TMA on the overall growth kinetics. To avoid any negative impact of the CVD component on the deposition rate and the film’s properties, we have also developed a kinetic model to correlate parameters like exposure times, partial pressures, purge times and deposition temperature to the CVD component in the growth. Additionally, we also looked into solutions to increase the deposition rate of the alucone films and amongst others found that using a bulkier precursor like DMAI instead of TMA can overcome the problem of precursor infiltration and increase the deposition rate of alucone processes by at least an order of magnitude. Upon detailed exploration, we also found that the alucone films prepared using DMAI are very much comparable to the ones prepared using TMA. We believe that the above work could be extended to other MLD systems and can serve as a guide in designing efficient MLD reactors.

Resume : Nanocomposite thin films are multifunctional coatings, consisting of nanoparticles embedded in a solid thin film matrix. Their high tunability have made them great candidates for various applications where innovative, simultaneous properties are needed. Ongoing research intends to provide a reliable process for the growth of high-quality nanocomposite coatings. Some of these attempts involve the injection of a liquid colloidal solution in non-thermal plasma deposition systems. The resulting plasma/aerosol environment is typically known as a misty plasma. Such a hybrid deposition process, combining low-temperature plasma deposition and pulsed injection of colloidal solutions, was recently developed by our group. A monodisperse TiO2 nano-colloidal solution is injected in the form of droplets in a low-pressure, inductively coupled RF plasma operated in O2/HMDSO gas mixtures for the growth of a SiO2 thin film matrix. The colloidal droplets are used to deliver the nanoparticles to the substrate while protecting them from the reactive plasma. Ideally, the liquid solvent evaporates during transport, leaving nothing but the nanoparticles on the surface of the sample, which will be quickly covered by the continuous deposition of the matrix. In this work, time-resolved optical emission spectroscopy and in situ spectroscopic ellipsometry are used to examine the kinetics driving nanocomposite thin film deposition by low-pressure misty plasma processes. It is found that the sharp pressure increase following pulsed liquid injection lowers the electron temperature and density, which mitigates the matrix deposition rate as the nanoparticles are supplied to the film. This effect creates alternating matrix-rich and nanoparticles-rich deposition periods, which can be used as an additional knob for judicious control of the film macroscopic properties

Resume : Diamond is potentially the best candidate for many applications in electronics, quantum technologies, optics, mechanics, thermal management or biomedical field, owing to its unique combination of physical and chemical properties. However, it is still incompatible with most of industrial processes because of several difficulties that have not yet been entirely overcome, especially limited synthesis areas (< 20 cm2) and necessary high deposition temperature (> 600 °C) in conventional reactors. To overcome these limitations, new deposition reactors were designed in order to allow the synthesis of diamond films on large area (> 300 cm2) and at low substrate temperature (< 400°C). Among these technologies, a distributed antenna array (DAA) microwave system [1], composed of 16 microwave plasma sources arranged in a 2D matrix and operating in H2/CH4/CO2 gas mixture, has been extensively used to produce nanocrystalline diamond (NCD) films suitable for applications requiring both thermal sensitive substrates and smooth as-grown surfaces [2-4]. In this work, we investigate the potentialities of NCD films produced in a DAA microwave system, operating at low temperature and low pressure, as protective coatings for optical devices. NCD films are synthesized on both borosilicate and soda-lime glass substrates and the influence of the substrate temperature and deposition time on the film microstructure and optical properties is examined. Optimal growth conditions are then determined for a substrate temperature below 300 °C leading to a growth rate around 50 nm.h-1 with homogeneous films formed of spherical aggregates composed of diamond grains of 12 nm in size. The resulting surface roughness is then very low, typically below 10 nm, and the diamond fraction is higher than 80 %. These properties lead to a high transmittance of the NCD/glass systems, above 75 %, and to a low absorption coefficient of the NCD film below 10^3 cm-1 in the visible range, whereas the resulting optical band gap is estimated at 3.55 eV. Such characteristics are suitable for optical applications of NCD films, especially for protective optical coatings. [1] L. Latrasse et al., Plasma Sources Sci. Technol. 16 (2006) 7. [2] D. Dekkar et al., Phys. Status Solidi (a), 215 (2018) 1800251. [3] D. Dekkar et al., Diam. Relat. Mater., 103 (2020) 107700. [4] D. Dekkar et al., J. Phys. D: Appl. Phys., 53 (2020) 455204.

Resume : During the last decade, HfO2-based materials are considered mainly as alternative dielectrics to SiO2 due to their high dielectric constant, while optical and luminescent properties of such materials are addressed only in a few reports. In this work, the impact of doping with rare-earth (RE) elements (Er, Nd, Pr) on crystalline structure evolution and optical properties of HfO2 and HfSiOx films is reported. The films were grown on Si substrates by radio frequency magnetron sputtering in argon plasma and annealed at TA=800-1100 oC for tA=15-60 min in a nitrogen atmosphere. The transformation of film properties was studied by means of SEM, EDX, XRD, TEM and photoluminescence (PL) techniques. For HfO2 films doped with RE ions, the stabilization of the tetragonal HfO2 phase in annealed films was observed contrary to the monoclinic structure of pure HfO2 films. The main reason responsible for this phenomenon is the formation of oxygen vacancies. For RE-doped HfSiOx films, phase separation between SiOx and HfO2 occurs upon annealing. For Nd or Er-doped films, the presence of RE ions was detected in SiOx and HfO2 phases, while for Pr ions they were found in the HfO2 phase only. This latter was transformed into cubic one up to 1050°C, while the formation of monoclinic HfO2 phase was detected after annealing at 1100°C. The shape of RE-related PL spectra followed the structural transformation. Narrow RE-related PL peaks were detected in the samples annealed at 1000-1100°C that confirms the location of RE ions in the phase with a high crystal field. The peculiarities of PL spectra and the mechanism of phase separation for different films are discussed.

Resume : Silicon carbide (SiC) is a wide bandgap semiconductor that is currently driving a profound evolution in power electronics, thanks to a unique combination of outstanding physical properties. In addition, SiC also exhibits very promising optical properties, making it very suited for applications in photonics, such as waveguides and frequency combs. For this purpose, amorphous SiC (a-SiC) thin films are deposited at very low temperature with the main challenges of controlling of bulk properties and the formation of perfect interfaces. Today, the relationship between the deposition conditions and the optical properties of the films is still not clear. This paper aims to provide a comprehensive picture of these relationships and finally to give some hints for further optimization. a-SiC thin films were deposited by Physical Vapor Deposition (PVD) on different types of substrates, such as sapphire and silica on silicon wafers, and using a polycrystalline SiC target as source material. The targeted properties were the refractive index and the attenuation coefficient of the film, measured by spectroscopic ellipsometry. A systematic investigation of the chemical and structural properties of the films was carried out, using a combination of XRD, FTIR and XPS. In parallel, control of the crystallization during the deposition or post-process annealing were performed to improve the understanding of the properties of the SiC thin film.

Resume : Over the years, a few types of biomaterials have been used, and perhaps the most broadly utilized category is addressed by metallic biomaterials. Among these, the biodegradable metallic materials played an important role in the clinical field, particularly in orthopedics, with various benefits to follow, mostly for the patient, but also for clinical staff. Additionally, they were also present in materials science, binding parts of bone regeneration and biocompatibility identified with structural analysis, mechanical and corrosion properties. As per the studies published in late years, Mg composites are biocompatible and biodegradable and can be utilized as implantable clinical devices, like bone implants, vascular stents, and so on. Despite the fact that they have great mechanical properties, with values near those of the human bone, it is wanted to further improve their electrochemical behavior. This aspect can be accomplished through addition of bioactive coatings with doped or undoped hydroxyapatite (HAp). The current paper aims to assess the electrochemical behavior of Mg alloys coated with Mg doped HAp. The deposition was made using the RF magnetron sputtering technique. The coatings were examined in terms of morphology, elemental composition, electrochemical behavior and roughness.

Resume : Stainless steels are widely used in hospitals and public transportation vehicles as one of the most common touch surfaces. Retrofitting stainless steel surfaces with an antimicrobial layer can bring potential public health benefits by reducing the ability of inanimate objects, or fomites, to transmit infections. Here we report a facile surface conversion reaction between stainless steel and a solution of KMnO4 and CuSO4, which leads to a conformal and robust oxyhydroxide layer. Microscopy observations show that the layer is amorphous, continuous, and pinhole free with a thickness of only 10-15 nm. The coating adheres strongly to stainless steel and can resist rubbing in simulated friction tests, which is attributed to its intermixing with the substrate without forming a sharp interface. Cu ions incorporated into the surface layer can be released into water droplets deposited on the surface and induce antimicrobial activities against bacteria (Pseudomonas aeruginosa PA14) after 30 min of contact.

Resume : Metallic thin films are central for technological applications such as microelectronics, optoelectronics and sensors thanks to their excellent electrical conductivity, high emissivity for infrared radiation and mechanical properties. In some applications, the film structure is expected to play a key role, for example as protective coatings against corrosion in reactive environments at high temperatures. Being able to tune the film structure is thus essential: Pulsed Laser Deposition (PLD) stands out as an alternative and promising deposition method to grow metallic thin films with tunable structure. We demonstrate that PLD enables the growth of fully amorphous and fully crystalline thin films for a well-known binary alloy, CuZr, by varying the substrate temperature during the deposition. Using x-ray photoelectron spectroscopy (XPS), we compare the corrosion behavior of CuZr for amorphous and crystalline films with identical composition. The results demonstrate the higher oxidation resistance of amorphous CuZr thin films. We attribute this effect to the presence of grain boundaries in polycrystalline films, which can act as diffusion channels and break-up points. These results pave the way to the synthesis of metallic thin films with superior and tunable properties for a wide variety of technological applications.

Resume : The use of thin films consisting of reduced graphene oxide and TiO2 (TiO2 -rGO) in solar harnessing devices is gaining momentum thanks to improved charge-transporting characteristics. In this report, we propose a facile spin-coating methodology for the deposition of crack-free TiO2 -rGO thin films. A range of characterization techniques has been utilized to confirm the formation of the TiO2 -rGO thin film. The improved charge-transporting properties of TiO2 -rGO composite thin films were confirmed by measuring the photoelectrochemical (PEC) activity under simulated solar light illumination. In particular, it was found that the TiO2 -rGO composite thin film yielded a better photocurrent response (~ 151.3 µA/cm 2 ) than the bare TiO2 thin film (~ 71.6 µA/cm 2 ) at 1.23 eV vs. the reversible hydrogen electrode (RHE). The obtained results suggested that rGO addition remarkably improves the charge-transporting properties in TiO2 films.

Resume : Air pollution that can lead to serious long-term adverse effects on the atmospheric environment and living organisms, as well as public health, has been regarded as one of the global risk factors for death and disability. According to the World Health Organization and the latest State of Global Air report, more than 90% of the world population lives in places that have unhealthy air. In 2017, regretfully, nearly 5 million deaths were linked with air pollution-related diseases and 147 million years of healthy life were lost. In light of the substantial threats to public health and quality of life brought about by air pollution, it is high time that we think of how we can protect human health and deal with particulate matter and volatile organic compounds in an efficient and economical manner. Herein, we demonstrate a dual-functional polyester fibrous air filter consisting of self-assembled titanium dioxide nanoparticles and percolated silver nanowires with high air permeability, and electrostatic particulate matter removal and photocatalytic formaldehyde decomposition abilities. The surface-functionalized polyester air filter reveals a remarkable particulate matter removal efficiency of up to 99.5% and a quality factor of 0.418 Pa−1 in heavy hazardous smoke, and it also retains a high removal efficiency of more than 87.4% after five filtration-cleaning cycles. Furthermore, with the aid of the decorated photocatalytic titanium dioxide nanoparticles, the same network can effectively degrade gaseous formaldehyde under UV irradiation. This strategy of surface-functionalizing nonwoven fabrics, which is reliable, easy-to-use, and low-cost, may open up promising alternative routes for tackling global air-pollution-related crises.

Resume : Pure bovine hydroxyapatite (BHA) and BHA doped with clinoptilolite (CLIN) and alumina (Al2O3) structures were synthesized by pulsed laser deposition with a KrF* excimer laser source onto Ti and Si substrates. The potential of these films to prevent the adhesion of bacteria and biofilm formation was investigated. The morphology of the PLD coatings consisted of aggregated/fused round-shaped micrometric particulates ranging from ~0.2 to ~6.3 µm. The complex stoichiometry of targets was well-reproduced in the deposited films. The XRD measurements indicated that coatings composed of BHA doped with a total of 10 wt.% Al2O3 and CLIN (in equal shares) consisted of an amorphous matrix with embedded BHA nano-crystallites, whilst in the case of 30 wt.% Al2O3 and CLIN doping (with equal shares), the deposited structures were completely amorphous. FTIR spectroscopy revealed the de-hydroxylation of BHA-Al2O3-CLIN composite coatings with respect to the simple BHA material. All tested coatings exhibited antibacterial properties against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa biofilms, as compared to control. The best compromise between a high cytocompatibility and a sustained antibacterial activity was reached in the case of the two BHA-CLIN-Al2O3 composite structures. The coupling of these two biological functionalities into structures containing sustainable and/or cheap materials, could be the key for the future development of performant implant coatings (which should be perfectly compatible with the surrounding tissue, while preventing post-surgical bacterial infections) or for application against nosocomial infections in health institutions. Acknowledgments: G.P.-P. acknowledges the financial support from a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0409 (PD 57/2020), within PNCDI III. G.P.-P. acknowledges, with thanks, the support under the national fellowship program L’Oréal UNESCO “For Women in Science”. C.R. and I.N.M. acknowledges the financial support from a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020-2030 (PCE113/2021), within PNCDI III.

Resume : We report on the fabrication of novel coatings with improved composition and structure that enhance bone structure restoring properties of titanium implants. Se and Sr doped HA/β-TCP coatings (HA/β-TCP:Se/Sr) were synthesize by combinatorial pulsed laser deposition (c-PLD) technique in order to identify the optimum elemental composition with respect to their biological performances. FTIR evaluation of HA/β-TCP:Se/Sr samples offered information’s about the functional groups and covalent bonding and confirmed the stoichiometric transfer of compounds. The elemental composition of the as-deposited coatings was determined from EDS and XPS measurements and pointed out the Se and Sr dopants content. The morphological features and the crystalline state of the as-deposited coatings were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, respectively. The cytotoxicity, viability and proliferation of HA/β-TCP:Se/Sr were evaluated in order to establish the optimal Se/Sr ratio for which the proliferation of osteoblasts precursors is ensured. The ELISA measurements showed that M2 polarization of mouse primary macrophages is diminished on HA/β-TCP coated Ti. Moreover, an attenuation of inflammatory response on areas with increased Se content was observed. The aim of this study was to fabricate metallic implantable devices covered with thin films of HA/β-TCP:Se/Sr composite designed for bone tissue therapy that stimulate the osseointegration. Acknowledgments: G.P.-P. acknowledges the financial support from a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0409 (PD 57/2020), within PNCDI III. G.P.-P. acknowledges, with thanks, the support under the national fellowship program L’Oréal UNESCO “For Women in Science”.

Resume : The mechanical properties, biocompatibility and fast dissolution of magnesium (Mg) alloys make them suitable for biomedical applications.[1] Despite these advantages, the successful application of Mg alloys as biodegradable materials has been hampered by their uncontrolled reactivity and propensity to corrosion, usually accompanied by hydrogen production and local alkalization, making one of its biggest advantages (fast dissolution) simultaneously a challenge [2-3] One way to overcome this issue is through application of surface treatments capable of decreasing the level of corrosion to an acceptable level of degradation.[4] These surface treatments can include chemical surface treatments and surface modification with coatings. In the present study, the influence of different pre-treatments on the surface morphology, electrochemical corrosion behavior and cytotoxicity of biodegradable Mg1Ca alloy has been studied. Mg1Ca was surface-treated with hydroxyapatite (HAp), aluminium oxide (Al2O3), phosphoric acid (H3PO4), hydrofluoric acid (HF) and acetic acid (CH3COOH). After the pre-treatments the phase content and chemical composition of the alloys were assessed through XRD and GDOES, respectively. Surface topography and morphology of the treated substrates were characterized by AFM and SEM. Corrosion behaviour of the pre-treated samples was analysed using EIS and the cytotoxicity of the materials evaluated trough WST-1 reduction and LDH release assays. After the pre-treatments, and with the exception of acetic acid pre-treatment, all samples presented a regular surface morphology. Furthermore, elemental composition analysis of the treated surfaces indicated that most of the formed films are thin. EIS allowed to observe that from all the pre-treatments tested, the HAp layer on Mg1Ca alloy, was the system that performed better in terms of corrosion. Cytotoxicity of the pre-treated Mg1Ca alloys revealed that the HAp and H3PO4 layer did not induce cytotoxicity, when compared to others and thus were considered non-toxic. References: [1]Li, N. and Zheng, Y., Novel Magnesium Alloys Developed for Biomedical Application: A Review. Journal of Materials Science & Technology, 2013, 29(6): p. 489 [2]Shadanbaz, S. and Dias, G.J., Calcium phosphate coatings on magnesium alloys for biomedical applications: A review. Acta Biomaterialia, 2012, 8(1): p. 20. [3]Neves, C.S., Sousa, I., Freitas, A.M., Moreira, L., Costa, C., Teixeira, J.P., Fraga, S., Pinto, E., Almeida, A., Scharnagl, N., Zheludkevich, M.L., Ferreira, M.G.S. and Tedim, J., Insights into corrosion behaviour of uncoated Mg alloys for biomedical applications in different aqueous media. Journal of Materials Research and Technology, 2021, 13:p.1908. [4] Hornberger, H., S. Virtanen, S. and A.R. Boccaccini, A.R., Biomedical coatings on magnesium alloys – A review, Acta Biomaterialia, 2012, 8(7): p.2442.

Resume : Thin film structures have found extensive applications in industry, such as micro-electronics, in the last decades. The stability of the thin films is of concern in many of these applications, specifically where the working temperature gets as high as hundreds of degrees. The film can undergo solid state dewetting at sufficiently high temperatures below the film material’s melting temperature. In this process, capillary forces break-up the film into isolated particles and islands, being detrimental for applications. Here, we investigate the solid-state dewetting behavior of CoxCu100-x thin films with three different compositions. Films were deposited by magnetron sputtering on (0001) sapphire, with compositions equal to 15, 38 and 75 at.% Co, and thicknesses of ~110 nm. In order to induce solid state dewetting, annealing treatments were performed in a mixed gas composition atmosphere (91% Ar, 9% H2), in a range of temperatures between 400 °C and 800 °C for 4 hours. Subsequently, an intense campaign of characterization has been carried out using scanning and transmission electron microscopies (SEM, TEM) and X-ray diffraction (XRD) techniques. Upon annealing, Cu-rich hillocks firstly form in the film before initiation of dewetting. The onset temperature of the formation of these hillocks depends on the composition of the alloy thin film. However, the number and size of these hillocks increase as the temperature increases in most of the compositions. Prior to dewetting, a phase separation of face-centered-cubic (FCC) Co and FCC Cu is found by XRD. Moreover, using electron backscatter diffraction (EBSD), we observed an increase in the grain size for both of these phases when increasing the annealing temperature. Besides, a change to (111) texture was observed for higher annealing temperatures as well as for a higher Co content. Interestingly, the actual dewetting initiates at lower temperatures in the films with larger Co content. Finally, we found that the dewetting is almost complete at 800 °C. We observed Cu-rich and Co-rich isolated particles and islands of the films containing the two kinds of phases. These particles have a FCC structure and adopt mostly two variants of a single orientation relationship (OR) with sapphire: Cu (111)±[110] ‖ Al2O3 (0001)[101̅0]. In previous studies, a similar OR has been found for Cu particles produced by solid state dewetting [1]. Concluding, a change in the composition of the CoCu thin films affects the formation, size and number of hillocks during the annealing process as well as the texture and initiation of dewetting. [1] Curiotto, Stefano, et al. "Orientation relationships of copper crystals on c-plane sapphire." Acta Materialia 59.13 (2011): 5320-5331.

Resume : Biomaterials play an important role in our society and are crucial for the society well-being, mainly since the rate of elderly population is increasing rapidly. Biomaterials are an important and integrated part of modern medicine and their development and improvement is essential. The fundamental requirement of a biomaterial is found to be in its interaction with its surrounding environment, with which it must coexist. Titanium (Ti) and its alloys are still considered the “golden standard” among the metallic biomaterials due to their remarkable properties. Moreover, to improve the osseoconductivity of metallic implants, the research community is trying to biofunctionalize the surface through various treatments. The aim of this study is to obtain hydroxyapatite (HAp) based coatings doped with Zn on Ti nanostructured surface through electrochemical techniques, and to evaluate the influence of Zn content on the physico-chemical properties of HAp. The nanostructured surface was obtained by anodic oxidation, which was carried out with a DC power supply system by applying a constant voltage of 20 V for 30 min at room temperature in 0.5 wt.% HF solution. After this stage, the samples were annealed at 450 °C for 2h. The nanostructured surfaces were coated with undoped HAp (H) and doped with Zn in two different concentrations to evaluate the influence of doping element on the properties of HAp. The deposition of the coatings was conducted by pulsed galvanostatic technique at 75 °C in an electrolyte that contain Ca(NO3)2∙4H2O, NH4H2PO4 and Zn(NO3)2, adjusted at a pH 5. The obtained materials were characterized in terms of morphology, elemental and phasic composition, chemical bonds, roughness, and adhesion. Also, the bioactivity and biocompatibility of the materials was assessed. The study revealed that the nanostructured surface consists in TiO2 nanotubes (NT) are highly oriented and uniformly distributed on the surface, with an average diameter of ~70 nm. In terms of phasic composition, XRD analysis highlighted that the NT present a mixture of anatase and rutile. Regarding the HAp coatings, it was evidenced that all samples presented a morphology made of ribbon-like crystals, which suffers some modifications after the addition and increment of Zn content. The XRD and FTIR spectrometry have confirmed that all coatings consist in HAp as a main phase. Irrespective of the Zn content, the crystallinity of the HAp coatings was enhanced after the addition of Zn. Compared to the undoped HAp, the average roughness of the coatings has decreased after addition of Zn, the smallest value being registered for the highest amount of Zn. The adherence assay has shown that the by increasing the Zn content the adhesion decreases. The bioactivity and cell viability assays have shown that addition of Zn in a small amount in the structure of HAp enhances the behavior of HAp, indicating their potential for medical applications. Acknowledgement: This research has been funded by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2019-1331, within PNCDI III (project no. TE 172/2020; 3B-CoatED).

Resume : Keywords: PVD; TFMGs; Ultrashort Laser Texturing; LIPSS; Biological behavior; Environmental SEM Discovered in the 1960s, metallic glasses are amorphous alloys usually resulting from the quenching of the molten alloy. Recent developments enable their fabrication as thin film metallic glasses (TFMGs) by co-sputtering techniques, making possible a wide composition range. In particular, the interesting bactericidal [1,2] or biocompatibility [3] properties of Zr-based TFMGs are the subject of numerous studies. Thanks to their biocompatibility, Zr-based, Ti-based, and Fe-based TFMGs are considered for bioimplants. Bactericidal compositions, usually containing Cu or Ag, were also developed. However, combining biocompatible and bactericidal properties is nearly impossible when relying only on the composition, as a surface which is toxic to bacteria is often also toxic to human cells. Therefore, another degree of freedom, such as the surface topography, has to be modified to meet the required biologic behavior toward bacteria on the one hand, and toward human cells on the other hand. These biological properties can then be monitored using surface texturing. It has been shown that a femtosecond laser could be used to generate multiscale surface structures called LIPSS (Laser Induced Periodic Surface Structures), on any material surface [4]. Those LIPSS are induced by light absorption phenomena that are highly dependent on the type of material, the irradiation fluence, and the surface state before irradiation. TFMGs exhibit extremely smooth surfaces of low roughness without defects such as grain boundaries or dislocations [5]. This specific surface state allows the creation of highly regular LIPSS with few bifurcations by ultrafast laser irradiation. Various kinds of LIPSS morphologies such as classical ripples, nanowells, or grooves can thus be obtained, which may influence the biological affinity of the modified surface. The goal of this work is to study the influence of femtosecond laser surface texturing on magnetron sputtered ZrCuAg TFMGs. The evolution of the surface topography and small-scale wettability (by environmental microscopy) will be determined and correlated with their biological properties. [1] G.I. Nkou Bouala et al.,“Silver influence on the antibacterial activity of multi-functional Zr-Cu based thin film metallic glasses“, Surface and Coatings Technology, 2018. [2] S. Comby-Dassonneville et al.,“ZrCuAg thin-film metallic glasses: toward biostatic durable advanced surfaces“, ACS Applied Materials and Interfaces, 2021. [3] S. Thanka Rajan et al., “Thin film metallic glasses for bioimplants and surgical tools: A review”, Journal of Alloys and Compounds, 2021. [4] J. Bonse et al.,“Laser-induced periodic surface structures (LIPSS)”, Handbook of Laser Micro- and Nano-Engineering, 2021. [5] M. Prudent et al.,“Initial morphology and feedback effects on laser-induced periodic nanostructuring of thin-film metallic glasses“, Nanomaterials, 2021.

Resume : Currently, the development of efficient antibacterial coatings is gathering great attention due to the constantly increasing hygienic demands worldwide. In this work, the antibacterial behavior of graphene and reduced graphene oxide coatings against Escherichia Coli was investigated in order to evaluate their photocatalytic activity and the underlying mechanisms. Graphene oxide (GO) was initially synthesized and chemically treated to obtain reduced graphene oxide (rGO-chem). Commercial graphene (Gr) and reduced graphene oxide (rGO) were also employed. All the materials were dispersed in isopropanol and deposited on glass substrates by spin coating. The materials were examined by XRD analysis and Raman spectroscopy. The observed crystalline and electronic structures were the typical for graphene and reduced graphene oxide, while their characteristic morphology was confirmed by SEM analysis. The antibacterial activity of the coatings against Escherichia coli was evaluated using viable-cell-counting method according to ISO 27447:2019. The coated, as well as non-coated substrates were set in required manner securing the same bacteria loading, humidity and light transmittance. The specimens were treated in dark and UV light and washed to collect the survived bacteria. After incubation, the percentage of the survived bacteria was determined with respect to a reference non-coated and non-treated specimen. The Gr coating showed remarkable antibacterial activity in both dark and UV light with survived bacteria to be only 8.8% and 1%, respectively. The outcome was ascribed to the mechanical disruption of the bacteria cells by the edges of the graphene sheets. The rGO coating appeared less active with survived bacteria 75.2% in dark and 33.7% in UV that was associated with the type of the reduction applied. The survived bacteria on the rGO-chem coating in dark and UV light was 49%, and 5.9%, respectively. This was ascribed to the semiconductor properties of rGO-chem and the presence of functional groups able to destroy the bacteria. Notably, high antibacterial activity was observed for the non-reduced GO coating. The percentage of survived bacteria in dark was 65.3% that can be connected to the layered structure of the material and the plethora of functional groups on the sheets’ surface remained after the oxidation of graphite. The increased activity under UV light (survived bacteria 11.9%) suggests semiconductor properties that could be caused by self-propagating reduction of the GO to rGO under UV irradiation. The conducted comparative investigation on antibacterial behavior of graphene and reduced graphene oxide in dark and UV light allows suitable type of graphene to be selected for specific application conditions. Acknowledgements: The financial support from the National Scientific Program “Petar Beron i NIE” contract number КП-06-ДБ/3 and “T1EDK-01729 CARBONGREEN” (MIS 5848538) projects is appreciated.

Resume : The research focuses on alternatives for surgical reconstruction by novel patient-specific, durable, biomimetic, bioactive and antibacterial implants for reconstruction of lost bone and joints. As part of the work carried out, a series of surface modifications were performed to improve the biocompatibility. A comparison of the influence of the phase composition on the microstructure of the materials obtained and the influence of the phase composition on the mechanical properties was carried out. Images of the surface topography were obtained by scanning electron microscopy at an accelerating voltage of 2kV. The images were obtained with a secondary electron detector. One of the images was taken with the table tilted to 52 degrees in order to obtain a three-dimensional image. Detailed microstructural characterisation was carried out using transmission electron microscopy on a cross section. A thin film was cut from the boundary between the substrate and the sphere. In the area of the sphere, the columnar nature of the crystallites was demonstrated for oxides and nitrides layers due to heat treatment. At the surface, a thin ~150nm fine crystalline layer was demonstrated. In the case of a substrate with a hexagonal structure, columnar growth of crystallites in the sphere region was shown in the direction perpendicular to the sphere surface. Twinning was also shown, due to the tendency for twinning in hcp structures. Twinning is one of the main deformation modes in hexagonal close-packed (HCP) metals, and it has a great influence on mechanical properties of HCP metals. Material properties were correlated with biological properties. The study of cytotoxicity and cell viability was carried out by a direct method (according to ISO 10993-5) using human fibroblast cells (PromoCell, DE), which consisted in determining the probability and number of necrotic cells on the analysed surfaces in relation to living cells (first method) and determining the amount of secreted lactate dehydrogenase from cells that were in direct contact with the surface (second method). The antimicrobial activity contact test was based on ISO 22196:2007(E). Escherichia coli strain ATCC 8739 (Gram-negative) and Staphylococcus aureus strain ATTC 6538P (gram-positive) were used, as recommended in the norm. Generaly, hydroxyapatite increases antibacterial properties (as stated in literature), as there is less bacteria than in reference samples. Obtained results are visualized as antibacterial activity index (R), which represents the difference between the number of viable bacteria recovered from both untreated and treated specimens. Material yields antibacterial properties if the calculated R value is greater than 2 (orders of magnitude/ it means 99% reduction of living bacteria ). The higher the R index is, the better the antibacterial properties are. As we can see the Hap coating greatly increases antibacterial activity, especially towards Staphylococcus aureus (gram-positive bacteria) Acknowlegement: The reported results were derived from a cooperative M-ERA.NET project called "fingerIMPLANT", which is co-funded by the Polish National Centre of Research and Development, Grant no. fingerIMPLANT M-ERA.NET2/2019/7/2020, and the Austrian Research and Promotion Agency, Grant no. 878515.

Resume : We report on hydroxyapatite (HA) of marine origin (derived from fish bones or sea-shells) synthesized by Pulsed laser deposition onto titanium substrates. Lithium phosphate, magnesium fluoride and silver were used as dopants in three different concentrations, of 0.5, 1 and 2 wt.%, respectively. The synthesized structures were investigated from the physical-chemical and mechanical points of view. SEM micrographs indicated surfaces with rough morphologies, made of particulates which were reported as friendly medium for cell cultures. XRD and FT-IR investigations demonstrated the synthesis of coatings with different degrees of crystallinity, generally influenced by the nature of the dopant/its concentration and the source material. Compositional analyzes evidenced the presence of trace-elements generally found in the composition of the bone mineral phase, which play a key-role in its functionality. Contact angle measurements revealed surfaces with a strong hydrophilic behavior. The inferred pull-out bonding strength adherence values were three times higher than the ones imposed by international standard (> 15 MPa) in the case of implant coatings with high biomechanical loads. Taking into consideration their improved mechanical characteristics and the morphological, structural and compositional results, along with the fact that the base materials are cheap and derived from sustainable resources, one can conclude that these marine-derived materials should be considered as viable candidates to HA synthetic ones, for implant coating applications. Acknowledgements: Project no. PN-III-P1-1.1-TE2019-1449 (TE 189/2021) and Core Programme 16N/2019.

Resume : Magnetic hyperthermia is an alternative method for cancer therapy. In the presence of RF magnetic field, magnetic nanoparticles generate heat which can increases the temperature in a controlled manner leading to apoptosis of the tumor cells. The interaction between nanoparticles and biological systems depends on the surface modification of magnetic nanoparticles. In our case, citric acid was used to enhance colloidal stability and biocompatibility of nanoparticles. Moreover, the efficiency of cancer therapy with magnetic hyperthermia could be enhanced by surface functionalization of magnetic nanoparticles with antitumoral drugs. In this study, we report the synthesis of superparamagnetic iron oxide nanoparticles (SPION) coated with citric acid with a Doxorubicin (Dox) loading efficiency of 50% when combining a solution of 400ppm nanoparticles with a solution of 80 ug/mL of Dox. Finite magnetisation at RT (100K above the Tb) of 6.5 emu/gram means that a fraction of nanoparticles are not in SPM regime. The broadening of the maximum of ZFC-FC curve for al samples indicates that the nanoparticles have a large distribution size in accordance to electron microscopy measurements. Biological in vitro tests on mouse B16F10 metastatic melanoma cells confirmed the internalization of magnetic nanoparticles delivering Dox. FACS results showed that the uptake of Dox from SPIONs is slower than the uptake of free drug. However, after 24 hrs, most cells (94-99%) have taken up Dox. This SPIONs formulation has an IC50 of 1.180 μg/mL at 72 hrs. Filtered SPION-cit-Dox induce 50% apoptotic cell death after 72h, as compared to 36% for bulk SPION-cit-Dox. We are further developing this formulation for preclinical tests in mice bearing melanoma tumors to determine its potential for application in cancer treatment.

Resume : Simple and doped hydroxyapatite coatings of various biological origin (BioHA) were synthesized by Pulsed Laser Deposition onto medical-grade titanium implants. The effect of different doping reagents on the physical-chemical, mechanical and biological properties of these structures was thoroughly assessed. The morphological investigations evidenced the fabrication of rough surfaces, which were demonstrated to determine a good adhesion of grown cells and in situ anchorage of implants. Structural evaluation indicated a monophasic apatite-like nature of the synthesized BioHA coatings. Compositional analyses revealed the presence of typical doping elements of natural bone, along with a quasi-stoichiometric target-to-substrate transfer. This is consistent with the biological nature of pristine materials. The inferred bonding strength adherence values were highly superior to the threshold imposed by ISO standard regulating load-bearing implant coatings. The PLD synthesized layers exhibited low cytotoxicity on human cell lines, along with a long-lasting effect against bacterial and fungal biofilm development. The good cytocompatibility and efficient antimicrobial activity, corroborated with a low fabrication cost from natural, sustainable resources, should recommend the herein proposed BioHA materials as innovative and viable substitutes of synthetic HA for the fabrication of a new generation of metallic implant coatings. Acknowledgements: Project number PN-III-P1-1.1-TE2019-1449 (TE 189/2021) and Core Programme 16N/2019.

Resume : Improving the prognosis of orthopaedic implant surgery requires the design of implant coatings with modulated osteoactivity and antimicrobrial properties at the implant site. Due to its biocompatibility and antimicrobial performance, gallium oxide (particularly as nano-sized features) is a promising coating component in implants. It is known that gallium ions inhibit osteoclast proliferation while having no effect on osteoblast proliferation. Furthermore, gallium oxide exhibits antimicrobial activity in thin film form. Herein, the potential of gallium oxide nanodots formed from Block Copolymer (BCP) patterns is examined by means of nanodot film characterisation and biological interaction. To investigate the efficacy of certain elements as potential biomedical nanomaterials, model structures of these dopants are required. Block copolymer (BCP) patterns are established as a means by which to create nanoscopic arrays of polymer or inorganic features. Nanodots of gallium oxide using BCP patterns were fabricated to test gallium’s biological impact. Poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) BCP film casting gave rise to a P4VP spherical body centred cubic (BCC) array within a PS matrix. Gallium nitrate solutions can selectively infiltrate the P4VP component and during post UV treatment, the polymeric material was fully removed leaving gallium oxide in situ in the P4VP geometry. The BCC spherical geometry of the nanodots was confirmed by AFM. Gallium oxide nanodot formation was facile, repeatable, and successful on silicon or titanium substrates. If required, the size of the dot could be altered within the nanometre range by variation of the BCP molecular weight. Gallium oxide nanodots had a water contact angle of between 60° to 80°, suitable for biological interactions. For this work gallium inclusion was confirmed by XPS and FTIR suggesting gallium oxide was present. To reveal the kinetics of gallium ionic release, ICP-MS data was collected from PBS solutions after sample immersion. Gallium ions up to a concentration of 0.1ppm were released and after 5 days the release was complete. Nutrient broth immersion tests confirmed the sterility of the process which was important in advance or any biological tests. Cell proliferation and cell viability studies with goat bone mesenchymal stem cells showed that the gallium oxide concentration used affected bone marrow cell proliferation in a concentration dependant manner. Bacterial inhibition zones around these samples showed that gallium oxide significantly inhibited the proliferation of E. coli and S. aureus. This study showed that BCP patterning is a suitable tool for creation of thin films to support biological testing. The gallium oxide nanodots formed demonstrated favourable osteoactivity and antimicrobial properties.

Resume : The aim of this work was to obtain and evaluate the cytotoxicity and antimicrobial activity of nanostructured bioactive coatings based on hydroxyapatite (HAp) nanoparticles and biomolecules. The results are intended for the improvement of the biological activity and limit the formation and development of Gram-positive and Gram-negative bacterial biofilms. Systematic investigations were performed on HAp coatings fabricated by laser technique on commercial grade 4 Titanium disks in order to obtain materials with anti-adherence and anti-biofilm effects. The antimicrobial effect against S. aureus and P. aeruginosa bacterial strains was investigated by IR spectroscopy and viable counts based assays. For biocompatibility studies, pre-osteoblasts were seeded in contact with the coatings at different time points, to assess cellular viability and proliferation potential by using MTT spectrophotometric and Live & Dead tests. The Ti surfaces modified with thin coatings containing hybrid systems revealed excellent biocompatibility and improved anti-microbial features, impairing the colonization and biofilm formation of relevant Gram positive bacteria and therefore, could be used to develop nano-modified coatings for more performant implantable devices. Acknowledgments: This work was supported by a grant of the Romanian Ministry of Education and Research, CCCDI - UEFISCDI, project number PN-III-P1-1.1-PD-2019-1185, within PNCDI III.

Resume : The purpose of this study was to obtain and evaluate a novel core/shell magnetite nanosystem functionalized with clove-derived eugenol (E), as well as to assess its impact on the most frequently isolated pathogens from skin infections, including strains responsible for G-tube-related complications. We investigated the potential of MAPLE-deposited thin coatings of magnetite nanoparticles to release biologically active E. The deposited coatings were characterized by SEM, XRD, DTA-TG and InfraRed Microscopy. In vitro cytotoxicity was evaluated by biochemical assays, while antimicrobial effect was assessed by viable counts in planktonic cultures and monospecific biofilms. The results of the microbiological analyses revealed significantly inhibition of growth in tested microbial pathogens. Besides excellent anti-adherence and antibiofilm effects, the proposed materials proved high biocompatibility, allowing the normal development and growth of human endothelial cells. This approach could be successfully applied for the optimization of medical devices’ surfaces in order to control and prevent microbial colonization and biofilm-associated infections. Acknowledgements: This work was supported by a grant of the Romanian Ministry of Education and Research, CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED-2019-3829, within PNCDI III.

Resume : The desirable self assembly (SA) of repeated 2D stacked layers requires a holistic analysis of three interconnected components: the electrode, the interface, and the molecular component; among them, the contact interface bears the largest burden of responsibilities. Epitaxial growth (EG) of coherent 2D + n stacked heterojunction by solvent?free deposition holds great promise, although the feasibility has never been demonstrated given multiple drawbacks (e.g., surface ligand effect, SLE). Here, it is demonstrated how a coherent 2D + n (n = 4) layered heterorganic film is grown on an archetypal Fe metal electrode [1]. The groundbreaking achievement is the result of the in vacuum integration of: i) chemical decoupling of the basal organic layer (a Zn?tetraphenylporphyrine, ZnTPP) from the metal electrode, ii) 2D ordering of the ZnTPP commensurate to the substrate, iii) rigid, stoichiometric, and orthogonally arranged, the molecule to molecule coupling between ZnTPP and a ditopic linear bridging ligand (i.e., DPNDI) guided by SA coordination chemistry, and iv) sharp (chemical) termination of the layered film. [1] A. Orbelli Biroli et al., Adv. Funct. Mater. 31 (2021) 2011008

Resume : The sol-gel process is a generic route for the liquid to solid transformation of materials. We concentrate in this study in the processing of WO3 to achieve WTe2-xSex thin films. Thin amorphous films of WO3 have been grown on Si by spin-coating of a sol-gel precursor and consolidated by ten minutes annealing treatments at 200, 400, 600 and 800ºC. Subsequently, a reduction process was carried out for 1 h at the same reference temperature in a partial atmosphere of H2. After this process, the films processed at temperatures of 600 and 800 ºC have transitioned to metallic tungsten with bcc and cubic crystalline structure, respectively. To achieve WTe2-xSex films, the samples reduced at 600 ºC were exposed to the chalcogenide vapors by isothermal closed space vapor transport [1]. This process was done at 600 ºC for 15 minutes in a partial atmosphere of H2. To characterize the samples, field emission scanning electron microscopy (FESEM) has been used together with EDAX, X-ray diffraction (XRD), ellipsometry, Rutherford backscattering spectroscopy (RBS) and Raman. On one hand, FESEM micrographs show that the sol-gel nucleated films are porous and amorphous. After annealing, XRD, ellipsometry and RBS confirm the presence of WO3, with increasing (metal) clusters after the reduction treatment. On the other hand, FESEM micrographs of tellurized/selenized samples show, for processing conditions at 600 ºC, crystalline microstructures in the form of nanobricks. Stoichiometry has been studied using XRD, EDAX, RBS and Raman, allowing to determine an excess of Te, which can be useful in the protection of the structures against oxidation. Additionally, femtosecond laser irradiation as a post-synthesis process to locally change the thin-film properties is explored. FESEM and Raman spectroscopy were used to identify the microstructural induced changes, ranging from a nano-pores formation to the formation of micrometric periodic structures inducing anisotropic properties. [1]O. de Melo. Journal of Materials Chemistry C, (6), 6799-6807, 2018.

Resume : Nanoscale metallic thin films are ubiquitous in many years in many technological applications, such as microelectronics, optoelectronics or energy conversion and storage. Over the years, numerous studies have demonstrated a complex dependence of the film microstructure and the resulting properties on the deposition conditions (i.e. the kinetic energy of the deposited particles, the nature and temperature of the substrate) and the characteristics of the deposited species (surface mobility, chemical reactivity). In this respect, the nature of the interfaces (chemistry, structure, spatial extent and roughness) is anticipated to strongly affect the subsequent film growth. Understanding the initial growth stages and their influence on the evolution of metallic thin film microstructure (grain size, texture, defect density) and properties (stress state, electrical conductivity) is the main objective of the INTEGRAL project funded by ANR. The central part of this project concerns the implementation of a robust and reliable multi-scale computer modeling of the growth of polycrystalline metallic thin films onto chemically reactive substrates on realistic time scales based on a kinetic Monte Carlo (kMC) Algorithm. The present contribution is focused on the first step of this multi-scale strategy. i.e. to provide a comprehensive ab initio study of the elementary mechanisms which occur during the first stages of the growth on Si (001) surface. The surface reactivity of the substrate is studied by computing using DFT the potential energy landscape (PES) of different metals, tungsten (W) and molybdenum (Mo), as archetype of low-mobility metals, and silver (Ag) and copper (Cu) as archetype for high-mobility. The most reactive surface sites can then be identified from PES and possible surface diffusion pathways, and their energy barrier, are discussed. We will also consider the formation of interfacial silicides layer that occurs during the early stages of metal growth under energetic conditions. For instance, we will show in the case of Mo that the incorporation of Mo atoms into the Si sublayer is thermodynamically favourable. The role of the concentration of the species introduced in the sub-layer on the stability of the silicide interface will be explored. Then, the possible formation of an interfacial alloy or phase transition by diffusion of species in the bulk will also be studied. Preliminary kinetic Monte Carlo results will be also presented.

Resume : One of the primary challenges faced by the materials science community is to understand the correlation among nanoscale atomic arrangement, structure-forming mechanisms, and mesoscale morphology during non-equilibrium material synthesis. Addressing this challenge will herald a new epoch in which tailor-made materials and devices with unprecedented macroscopic behavior will be created by controlling mesoscale structure via nanoscale manipulation. The present talk demonstrates the implementation of the above-outlined concept of multiscale materials design during the vapor-based synthesis of thin noble-metal films (and nanostructures) on weakly-interacting substrates, including oxides and van der Waals crystals. Such film/substrate systems exhibit a pronounced and uncontrolled three-dimensional (3D) morphology, which is a major obstacle toward fabricating high-quality multifunctional metal contacts in a wide array of devices. Using growth of sliver (Ag) on silicon dioxide (SiO2) as a model system—along with a combination of in situ film growth monitoring, ex situ microstructure and chemical characterization, and modelling—it is shown that the tendency for 3D growth morphology can be effectively reversed, without compromising key physical properties of the film and the substrate, when miniscule amounts of minority gaseous and metal species (surfactants) are deployed with high temporal precision at the film growth front, such that atomic-scale processes that govern key film-formation stages are selectively targeted and affected. The talk concludes with a discussion with regards to the implications and possibilities that this strategy opens for tuning macroscopic performance of devices in the areas of energy saving, energy generation, and nanoelectronics.

Resume : III-N materials are commonly used as active layers in LEDs, transistors, solar cells and mechanical devices(1, 2). The main spinneret is based on the use of InGaN alloys. However, such layers contain indium and gallium. Significant volatility in their price and supply over the last years has led to considerable concern given their critical roles and their use in a wide range of large-scale electronic devices. It is important to study and develop new earth abundant materials with optimized properties for the realization of innovative optoelectronic devices that could be competitive cost for mass production. Over the past 10 years, the study of Zn based II-IV-N2 family has shown that they are interesting semiconductors due to the tunability of their properties. However, oxygen contamination and high vapor pressure of zinc make it difficult to control the stoichiometry and the structure order. In this work, we aim at developing a new kind of inexpensive, indium/gallium-free, nitride material that could be the basis of new way for optoelectronic applications. The studies are focusing on MgSnN2 thin films (bandgap energy ≈ 2 eV) that is a good candidate for green emitters in LEDs and an absorber material in tandem photovoltaics(3). MgSnN2 thin films have been deposited by magnetron co-sputtering at different substrate temperatures (up to 500 °C). The Mg/Sn atomic ratio has been controlled by the current applied to the Mg and Sn targets. The structure of the films has been studied by X-ray diffraction. Whatever the deposition temperature, the films crystallize in a wurtzite-like structure with a strong preferred orientation in the [001] direction. The columnar microstructure of MgSnN2 thin films have been studied by transmission electron microscopy and the chemical environment of the Sn and Mg atoms has been investigated using Mössbauer spectrometry and X-ray photoemission spectroscopy. The optical band gap deduced from UV-visible spectroscopy is ranging in the 2.1 – 2.4 eV range. These experimental optical properties of MgSnN2 films were compared to those obtained by ab initio calculations. Finally, the electrical resistivity, carrier concentration, type and carrier mobility have been measured by Hall effect. (1) Nakamura, S.; Senoh, M.; Nagahama, S.; Iwasa, N.; Yamada, T.; Matsushita, T.; Kiyoku, H.; Sugimoto, Y.; Kozaki, T.; Umemoto, H.; Sano, M.; Chocho, K. InGaN/GaN/AlGaN-Based Laser Diodes with Modulation-Doped Strained-Layer Superlattices Grown on an Epitaxially Laterally Overgrown GaN Substrate. Appl. Phys. Lett. 1998, 72 (2), 211–213. (2) Amano, H.; Sawaki, N.; Akasaki, I.; Toyoda, Y. Metalorganic Vapor Phase Epitaxial Growth of a High Quality GaN Film Using an AlN Buffer Layer. Appl. Phys. Lett. 1986, 48 (5), 353–355. (3) Yamada, N.; Matsuura, K.; Imura, M.; Murata, H.; Kawamura, F. Composition-Dependent Properties of Wurtzite-Type Mg1+xSn1–XN2 Epitaxially Grown on GaN(001) Templates. ACS Appl. Electron. Mater. 2021 3 (3) 1341-1349.

Resume : The growth of thin films on planar and nanostructured substrates is studied by means of coarse-grained kinetic Monte Carlo simulations under conditions typically encountered in Plasma Enhanced Chemical Vapor Deposition experiments. The basis of our approach is known to work well to simulate the growth of amorphous materials using cubic grids and have been extended here to reproduce not only the morphological characteristics and scaling properties of amorphous TiO2 but also the growth of materials with very different structural characteristics, like polycrystalline wurtzite-type ZnO and adamantane. The results of the simulations have been compared with available experimental data obtained by X-Ray Diffraction, analysis of the texture coefficients, Atomic Force Microscopy, and Scanning Electron Microscopy. The model is shown to reproduce with a good approximation many relevant features of the real samples.

Resume : Amorphous materials, such as amorphous alloys and metallic glasses (MGs) [1-4] are of current interest due to their unusual properties [5-8] like high strength, good corrosion resistance, and much higher hardness than crystalline alloys of comparable elastic modulus. Further, the combination of crystalline and amorphous layers represents a promising route for the design of multilayered coatings with improved mechanical properties [9]. Because glassy alloys do not exist in thermodynamic equilibrium, they undergo crystallization with the supply of thermal energy. However, despite decades of experimental and theoretical efforts, many questions regarding the details of these processes remain still open. Due to the small space scales involved, the experimental investigation of the mechanisms underlying the phase formations caused by strain/stress as well as during nanoindentation on amorphous materials is difficult. Fortunately, the fast increase in available computation power is today allowing more and more accurate and larger size molecular dynamics (MD) simulations of almost any kind of system. In this work, the crystallization of refractory metals (W, Nb, Ta, V, Mo) has been examined by means of molecular dynamics simulations. All these metals are more stable in their usual bcc structure, so under indentation, a growth of bcc crystals around the indenter is observed. The velocity at which this process occurs depends on various factors like the type of metal and the initial conditions of the amorphous sample. Similarly, the structure of the resulting grain boundaries and grain size average depends on the structural and thermodynamical properties of these metals. A simple model correlating crystal-forming ability (CFA) with thermodynamic properties will be presented. The model provides a guide towards the use of amorphous metals (or alloys) in novel materials design. References: 1. KLEMENT, W., WILLENS, R. and DUWEZ, P., 1960. Non-crystalline Structure in Solidified Gold–Silicon Alloys. Nature, 187(4740), pp.869-870. 2. Johnson, W., 1999. Bulk Glass-Forming Metallic Alloys: Science and Technology. MRS Bulletin, 24(10), pp.42-56. 3. Inoue, A., 2000. Stabilization of metallic supercooled liquid and bulk amorphous alloys. Acta Materialia, 48(1), pp.279-306. 4. Greer, A.L., 2014. Metallic glasses. Physical metallurgy, pp.305-385. 5. GASKELL, P., 1978. A new structural model for transition metal–metalloid glasses. Nature, 276(5687), pp.484-485. 6. Miracle, D., 2004. A structural model for metallic glasses. Nature Materials, 3(10), pp.697-702. 7. Sheng, H., Luo, W., Alamgir, F., Bai, J. and Ma, E., 2006. Atomic packing and short-to-medium-range order in metallic glasses. Nature, 439(7075), pp.419-425. 8. Ma, E., 2015. Tuning order in disorder. Nature Materials, 14(6), pp.547-552. 9.Yavas, H., Fraile, A., Huminiuc, T., Sen, H., Frutos, E. and Polcar, T., 2019. Deformation-Controlled Design of Metallic Nanocomposites. ACS Applied Materials & Interfaces, 11(49), pp.46296-46302.

Resume : Vapor-based synthesis of ultrathin metallic films on weakly interacting substrates (2D materials, dielectric surfaces) is a key step for fabricating heterostructure devices in the areas of optoelectronics, energy saving and energy conversion. Experimental results have shown that the layer morphology and substrate coverage can be controlled by different means. A simple growth manipulation strategy consists in performing a multistep deposition process in which growth interrupts are involved. Interrupting the deposition process allows the system to dynamically evolve (relaxation), with consequences on island aspect ratio, film continuity and optical/electronic performance. Prior work using real-time growth monitoring of polycrystalline Cu films on SiO2 substrate has revealed that the thickness at which the film becomes continuous (i.e. full coverage of the substrate) is affected by growth interrupts, but in opposite way depending whether the interruption of the deposition process occurs before or after the percolation threshold (electrical conductivity). To better understand these experimental findings, we have performed atomistic simulations using Kinetic Monte Carlo (KMC) method. A dedicated KMC model based on a 3D rigid lattice has been developed to study the growth of sputter-deposited Cu thin films. The model takes into account the angular and energy distributions of the incoming particles, as provided by SRIM and SIMTRA calculations. Beside deposition and diffusion events, atomistic mechanisms relevant to growth under energetic deposition conditions, such as re-sputtering, directionally-induced surface diffusion and bulk defect creation, have been explicitly taken into account. The anisotropy of Cu surface diffusion has been taken into account as well. We show here preliminary simulation results about the effect of multistep deposition process for a homoepitaxial system (Cu on Cu(001)). All simulations have been performed at the same temperature, 350K. The initial deposition time has been chosen in such a way that the relaxation period starts before and after the 2D percolation of the deposited film. Different deposition rates (1ML/s and 10ML/s) and relaxation times (0.5s and 1.0s) have been also considered. The simulation results show that the thickness at which the film becomes continuous is delayed (resp. anticipated) when the interruption of the deposition process occurs before (resp. after) percolation, in a qualitative agreement with the experimental results mentioned above. Our model being a rigid lattice model, a better agreement with the experimental data corresponding to Cu deposition on SiO2 is expected by simulating in the future a heteroepitaxial growth.

Resume : The recently-observed(1) self-assembly of salphen-based metal-organic frameworks (MOF) into networks of interconnected microrings with nano-thin strings may suggests a new intriguing tool for nanoscale patterning. Such patterning is highly desired for design of functional materials in energy applications. However, the mechanism of this phenomenon yet needs to be clarified. In this work we use ab initio calculations and all atomic molecular dynamics simulations in explicit together with umbrella sampling and free energy perturbation to investigate conformational space of the bis-salphen MOFs and potential self-assembly pathways. We have previously shown (2) that a particular conformation of the bis-salphen MOF allows it to form dimeric units, linking with other units via pi-pi and coordination interactions, forming to supramolecular chains, sheets and tubes, with highly variable mechanical properties controllable by the choice of solvent. Here we present an in-depth abinitial and molecular dynamics study of conformational change of such dimeric units under stresses, occurring in self-assembled chains during solvent evaporation and consequent growth of the network. Our findings illuminate the details of the relation between microscopic structure – macroscopic mechanics of self-assembling networks of bis-salphen compounds and help understanding how the forming nanostructured pattern can be controlled. Combined with the demonstrated ability of such networks to align carbon nanotubes (1) this opens the path to develop highly transparent and conductive films for transparent electrodes for flexible solar cells and LED illumination panels. References: 1. Escárcega-Bobadilla M V, Zelada-Guillén G a, Pyrlin S V, Wegrzyn M, Ramos MMD, Giménez E, et al. Nanorings and rods interconnected by self-assembly mimicking an artificial network of neurons. Nat Commun [Internet]. 2013 Nov 1 [cited 2014 Jun 28];4(May):2648. Available from: http://www.nature.com/doifinder/10.1038/ncomms3648 2. Pyrlin S V., Hine NDM, Kleij AW, Ramos MMD. Self-assembly of bis-salphen compounds: from semiflexible chains to webs of nanorings. Soft Matter [Internet]. 2018 [cited 2018 Jan 13];14(7):1181–94. Available from: http://pubs.rsc.org/en/Content/ArticleLanding/2018/SM/C7SM02371E

Resume : Diamond like amorphous carbon (DLC) film received significant interest duo to the very interesting combination of the high hardness (up to 80% of diamond hardness), low friction, chemical inertness, biocompatibility, optical transparency and possibility to control electrical properties in wide range. Combination of the diamond-like carbon properties mentioned above with ultra-low water wetting angle is interesting for different anti-fogging and anti-fouling application. In present research diamond like carbon films containing nitrogen and DLC films containing SiOx were fabricated by reactive DC magnetron sputtering, reactive high power pulse magnetron sputtering and ion beam deposition by anode layer ion source. Structure of the films was investigated by Raman scattering spectroscopy. Composition of the films was studied by X-ray photoelectron spectroscopy. Surface morphology was researched by atomic force microscopy. Hydrophilic nature of the films was studied by evaluating surface contact angle. Ultra-low surface contact angle DLC films were fabricated by setting appropriate deposition conditions.

Resume : Nanomultilayer (NML) materials are commonly formed by alternatively stacking nanolayers of a metal or an alloy, oxide or nitrides of two or more dissimilar materials. Their very flexible design criteria make them functional architecture for many applications as low temperature joining technologies, op-tical and radiation-tolerant coatings. They are mainly produced by physical vapor deposition (PVD) and in particular by magnetron sputtering, where a full control on thickness, period and interface roughness can be achieved with deposition parameters tuning. During the growing procedure, internal residual stress is generated in the forming multilayer. Stress represents one of the main factors de-termining failure and reliability issues and affecting the durability and the performance of functional coatings. Nevertheless, for some specific applications, a controlled level of stress is desirable to en-hance target properties like mechanical strength, thermal stability and thermal conductivity. For this reason, it is of paramount importance to study the relation between deposition parameters and stress states in NMLs. Copper-tungsten (Cu/W) multilayers are one of the most widely used nanomaterials in electronic, optical, and sensing devices for the electrical properties of Cu in combination with the me-chanical strength of W. In this work, Cu/W multilayers have been fabricated with opposite stress val-ues (i.e. tensile and compressive) by specific tuning of the growth parameters. The effect of tensile and compressive stress on microstructure, thermal properties and stability have been investigated. Stress derived from in-situ substrate curvature measurements has been compared with stress meas-ured ex-situ by XRD. The difference between the stress values obtained with these two techniques has been ascribed to interface stress, whose values have opposite signs in the tensile and in the compressive multilayers. Along with the stress state, also the change in microstructure has been characterized and correlated to the internal stress. Different techniques (SEM, TEM, XRD and sputter depth profiles acquired with XPS) have shown that the tensile NML has a more disordered structure than the compressive. The different microstructure and stress state have been observed to affect also properties like thermal stability upon annealing and the thermal conductivity of the NMLs. The com-pressive system displays higher resistance to degradation when annealed at high temperature and it has a higher thermal conductivity. This works paves the way to stress tailoring in multilayers for spe-cific properties and applications.

Resume : Full Heusler alloys such as Co2FeSi (CFS) have high Curie temperatures and a predicted 100% spin polarization at the Fermi level making them ideal candidates for spintronic devices [1]. Moreover, CFS has a huge potential for large scale integration into spintronic devices due to the excellent lattice match with Si. The half-metallicity is predicted to be a feature of the L21 ordering of CFS which is significantly reduced when the Fe-Si sublattice is disordered i.e. B2 ordering. Typically, CFS grows in the B2 phase at low temperatures (T< x), and transitions to the L21 phase with thermal annealing between 500°C and 700°C. However, at these annealing temperatures Si diffusion from the substrate reduces the magnetization and spin polarization close to the interface [2]. In this work, we study the magnetic and structural properties of epitaxial CFS films grown on Si(111) substrates at room temperature by MBE. Using X-ray diffraction (XRD) and aberration-corrected scanning transmission electron microscopy (STEM), we show that the as-prepared films exhibit mixed L21 and B2 ordering without the need of annealing. When the L21 ordering is present, we observe a reduction of the ferromagnetic resonance (FMR) linewidth. Interestingly, even at a low growth temperatures of <130°C, interfacial effects have an impact on the magnetic anisotropy of the films which act to switch the magnetic easy axis (EA) from [10-1] to [1-10]. HAADF-STEM images show the changes at the CFS/Si interface as a function of the growth temperatures. Further microscopy experiments are currently under way in order to fully correlate the magnetic and structural properties of the CFS/Si heterostructure. References: [1] B. Balke, S. Wurmehl, G. H. Fecher, C. Felser, and J. Kübler, Sci. Technol. Adv. Mater. 9, 014102 (2008) [2] B. Kuerbanjiang et al, Appl. Phys. Lett., 108, 172412 (2016).

Resume : With the need for green and sustainable energy growing higher research has focused towards new photocatalytic materials and the performance enhancement of existing ones. Lately Bi-based materials have shown a great potential for such applications due to their low toxicity, low solubility and corrosion resistance. Indeed, recently produced thin films of Bi/Bi2O3 and Bi/BiOxFy exhibit a higher degree of photocatalytic activity in pollutant degradation and in photoconversion of CO2 to CO compared to their powder counterparts. To further enhance their performance the present work demonstrates a novel process for deposition of these Bi-based materials in nanoparticles (NPs) via magnetron sputtering onto 1-butyl-3-methylimidazonium bis(trifluoro-methylsulfonyl)imide [BMIM][NTf2] ionic liquid (IL). IL has gained great interest for obtaining NPs of high purity and controlled size, as it acts as stabilizing mechanism for the produced particles. However, to this day, IL has been employed as substrate only for the elaboration of metallic nanoparticles. Therefore, the goal of this work was to synthesize semiconductor Bi-based NPs by injecting various reactive gases during the Bi target sputtering. DLS and SAXS analysis show that the elaborated NPs exhibit a narrow size distribution (diameter <20 nm), thus, increasing effectively the specific surface area (about x100 compared to thin film) and enabling to take advantage of the plasmonic effect. TEM observations further confirm a well-dispersed, non-agglomerated spherical particle formation. Controlling the reactive gas (Ar/O2/CF4) ratio allows to tune the desired composition of the NPs, from pure metallic bismuth to mixtures of metallic phase and oxide or oxyfluoride phases. XPS characterization reveals the presence of Bi0 as well as Bi+3 state indicating the successful formation of these phases. Finally, their photocatalytic efficiency in photodegradation and photoconversion will be presented.

Resume : TiO2 thin films have attracted large interest due to their photocatalytic and super-wetting properties, thus being attractive for self-cleaning, air and water cleaning, self-disinfecting and/or hydrophilic surface treatments. The anatase polymorph is considered to be the most active photocatalytic phase, and methods to prepare well-defined anatase thin films are therefore of utmost importance. Ideally, the deposition should be done at a sufficiently low temperature to be compatible with a variety of substrates, including polymers. High power impulse magnetron sputtering (HiPIMS) is regarded as one of the most promising PVD techniques for deposition of metal and compound materials, and has been reported to allow the synthesis of anatase TiO2 close to room temperature (RT). This is attributed to the ionization of the sputtered species in contrast to the standard magnetron sputtering. By ionizing part of the sputtered flux, sufficiently high energy of the imprinting ions can be achieved to promote surface diffusion and nucleation and crystal growth without applying substrate annealing. In this contribution, we report the deposition of TiO2 thin films by reactive HiPIMS and pulsed direct current magnetron sputtering (p-DCMS) with focus on its photocatalytic activity. A wide range of deposition conditions were investigated in order to promote crystallization. The influence of the deposition temperature, oxygen flow, substrate biasing, as well as different pulse configurations in HiPIMS were evaluated. Additionally, both metal (MM) and oxide modes (OM) of deposition were studied since the ion population in the sputtered flux is significantly different. The photocatalytic activity was assessed by measuring the photo-degradation of stearic acid by in situ FTIR spectroscopy. Furthermore, the film structure and morphology were studied by grazing incidence XRD and SEM. Our results show that films deposited by HiPIMS without any substrate heating present larger photoactivity than the corresponding p-DCMS despite being apparent XRD amorphous, but are also almost one order of magnitude less active than the heated films produced by HiPIMS. This difference with respect to higher deposition temperatures can be attributed to the crystallization of the TiO2, which we tentatively attribute to the microstructure of the HiPIMS films. HiPIMS pulse variations and substrate biasing were not sufficient to achieve the crystallization in RT depositions. Despite using distinct pulse duty cycles – 1 and 10% – aiming to increase the ion population, no evident difference in photoactivity was observed, and increasing the ion energy through substrate biasing resulted in denser films but with reduced photocatalytic activity. However, the mode of deposition had strong impact on the films’ activity. OM granted generally more active films than the MM, and the anatase phase was achieved at a lower deposition temperature, 200˚C. Interestingly, at the same temperature, all MM films shown traces of Rutile, specially under more energetic conditions, while the first hints of anatase were seen at 400˚C. Finally, we discuss the effect of different seed layers, i.e. deposition on single-crystalline LAO and ITO-coated substrates as well as differences in the crystallization kinetics.

Resume : For atomic layer deposition (ALD) of noble metals, processes with ozone co-reactant always allow lower deposition temperature, compared with those with oxygen. However, Pd and Rh ALD processes using ozone as the co-reactant were limited. For Pd ALD, previous studies on precursor Pd(hfac)2 coordinated with an oxidizing agent as the co-reactant failed in fabricating metallic thin film. Instead, explosive hydrogen has been always applied as the co-reactant, which bring safety concerns. For Rh ALD, oxide products were always obtained by using Rh(acac)3 as the precursor, ozone as the co-reactant. In this work, Pd and Rh metallic thin films were fabricated by using ozone as the only co-reactant. It was discovered that not only the deposition temperature, but also the ozone concentration contributes to the ALD products. The growth of the thin films showed self-limiting property of ALD technique and the morphology with various deposition cycles at different temperatures help extend the understanding of the nucleation of Pd and Rh.

Resume : The use of contact lubricants for current-carrying plug connections is the common standard technology in electrical power engineering. The aim of the project is to develop a galvanic silver dispersion coating with self-lubricating properties as an alternative. The particles, in the form of powders, are dispersed into a metal matrix electrolyte and kept in suspension by appropriate electrolyte circulation. The particle incorporation into the silver layer can be controlled by a suitable choice of process and electrolyte parameters [1]. Within the scope of this project, it was possible to incorporate various particles of known solid lubricants (graphite, hBN, SiC, MoS2, WS2, Bi2S3 and SnS) into a silver matrix electrochemical deposition [2-3]. Ag-graphite was used as a reference system for evaluating the friction and wear behavior of the other particles. The dispersion depositions with hBN, SiC, Bi2S3 and SnS showed no significant improvement of the co-efficient of friction compared to pure silver. Only MoS2 and WS2 particles improved the tribology properties of the silver particle dispersion depositions by a significant amount, with co-efficient of friction 0.32 and 0.26 respectively. In addition to the co-efficient of friction, the surface wear was also analyzed with light microscope comparisons and confocal microscopy 3D representations. [1] J. Meyer/ T. Sörgel (2013): Chemische und elektrochemische Dispersionsbeschichtung, in WOMag, Waldshut-Tiegen, Deutschland: WOTech, Jg. 2013, Nr. 9. [2] R. Hartung/ J. Schmidt/ S. Both (2008): Tribologische Nickel-Dispersionsschichten mit hexagonalem Bornitrid, in Galvanotechnik, Bad Saulgau, Deutschland: Eugen G. Leuze Verlag KG. Jg. 2008, Nr. 12, S. 2931-2939 [3] R. Arnet/ A-K. Egetenmeyer/ H. Kappl/ H. Willig (2021): Silberdispersionsschichten mit selbstschmierenden Eigenschaften, in Galvanotechnik, Bad Saulgau, Deutschland: Eugen G. Leuze Verlag KG. Jg. 2021, Nr. 1, S. 21-30

Resume : Crystalline vanadium sesquioxide (V2O3) undergoes a metal-to-insulator transition (MIT) at a temperature around 155 K, with the conductive phase above the transition temperature. Crystalline V2O3 thin films have been synthesized by various deposition techniques and typically require substrate temperatures above 400 °C. Such high deposition temperatures limit the application of this material for growth on temperature-sensitive substrates. Here, we show the deposition of crystalline V2O3 film at relatively low substrate temperatures (≤ 200 °C) using reactive high power impulse magnetron sputtering (HiPIMS) from a vanadium target. HiPIMS is a deposition technique that combines magnetron sputtering with pulsed power concepts, in which large fractions of sputtered atoms are ionized by applying power in pulses of high amplitude and low duty cycle. The flux of ionized film-forming species onto the substrate facilitates crystallization in the growing film due to increased surface mobility of adatoms. We discuss the choice of deposition parameters such as the working gas pressure and the oxygen flow rate. The resulting films were investigated for crystallinity and phase distribution, grain size, surface morphology, and cross-sectional microstructure. The MIT behavior of the V2O3 films was measured by a physical property measurement system (PPMS) at temperatures ranging from 300 K down to 2 K. We conclude that highly crystalline V2O3 films can be grown using the HiPIMS process at relatively low substrate temperatures. Since the principle may not be limited to V2O3, this may open new possibilities for future applications where low temperature deposition of crystalline films is essential.

Resume : Thin films from fish bones-derived (Sparus aurata and Salmo salar species) bi-phasic calcium phosphate materials were fabricated via pulsed laser deposition with a KrF* excimer laser source (λ = 248 nm, τFWHM ≤ 25 ns). Physical–chemical characteristics of targets and deposited nanostructures were assessed by SEM and XRD, and also by Energy Dispersive X-ray (EDX) and FTIR spectroscopy. The as-deposited films were Ca-deficient and contained a significant fraction of β-tricalcium phosphate apart from hydroxyapatite, which could contribute to an increased solubility and an improved biocompatibility for bone regeneration applications. The synthetized coatings proved efficient against Escherichia coli colonization, while presenting unchanged cytocompatibility with human gingival fibroblast cells in respect to the biological control, making them promising for fast osseointegration implants. Progress is therefore expected due to optimum biological activity profiles (combining antimicrobial, anti-inflammatory and regenerative properties) associated with the use of natural and inexpensive materials for advanced implant coatings. Acknowledgments: G.P.-P. acknowledges the financial support from a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0409 (PD 57/2020), within PNCDI III. G.P.-P. acknowledges, with thanks, the support under the national fellowship program L’Oréal UNESCO “For Women in Science”. C.R. and I.N.M. acknowledges the financial support from a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020-2030 (PCE113/2021), within PNCDI III.

Resume : The monolithic integration of nanostructured quartz films on silicon substrates is a key issue for the future development of piezoelectric devices as prospective sensors with applications based on the operation in the high frequency range. However, to date it has not been possible to make existing quartz manufacturing methods compatible with integration on silicon and structuration by top-down lithographic techniques. Here we report unprecedented controlled large-scale crystallization of nanostructured epitaxial quartz films on silicon substrates by the combination of soft-chemistry and three lithographic techniques: (i) laser transfer lithography, (ii) soft nanoimprint lithography on Sr-doped SiO2 sol-gel thin films and (iii) self-assembled SrCO3 nanoparticles reactive nanomasks [1,2]. Highly ordered 1D quartz patterns consisting of vertical quartz nanocolumns with diameters and heights ranging from 50 nm to 800 nm and from 200 nm to 2 µm, respectively have been obtained by using scalable lithographic methodologies that do not require masks. 1D-quartz nanostructures maintain the crystallinity, epitaxial orientation and piezoelectric properties. We quantify the piezoelectric coefficient of nanostructured quartz films by using PFM and Direct PFM method recently developed by the authors [3]. This work demonstrates the complementarity of soft-chemistry and top-down lithographic techniques for the patterning of epitaxial quartz thin films on silicon while preserving its epitaxial crystallinity and piezoelectric properties. These results open the door to the development of a cost-effective on-chip integration of nanostructured piezoelectric α-quartz MEMS [4,5] with enhanced sensing properties of relevance in different fields of application such as biology [6]. [1] D Sánchez-Fuentes et al. Micro/Nanostructure Engineering of Epitaxial Piezoelectric α-Quartz Thin Films on Silicon. ACS Appl. Mater. Interfaces 2020, 12, 4, 4732–4740 [2] Qianzhe Zhang, David Sánchez-Fuentes et al. Tailoring the crystal growth of quartz on silicon for patterning epitaxial piezoelectric films. Nanoscale Advances 2 2019 [3] Andres Gomez, Piezo-generated charge mapping revealed through direct piezoelectric force microspocy. Nature Communications, 8 (1113) (2017). [4] Claire Jolly, David Sánchez-Fuentes et al. Soft chemistry assisted On-chip Integration of Nanostructured quartz-based Piezoelectric Microelectromechanical System. Adv. Mater. Technol. 2021, 6, 2000831. [5] Claire Jolly, David Sánchez-Fuentes et al. Epitaxial Nanostructured α-Quartz Films on Silicon: From the Material to New Devices. J. Vis. Exp;(164), e61766, doi:10.3791/61766 (2020). [6] D. Sanchez-Fuentes et al, Mapping Cell Membrane Organization and Dynamics Using Soft Nanoimprint Lithography. ACS Appl. Mater. Interfaces 2020, 12, 26, 29000–29012.

Resume : The advantages of implants are notorious, both from a functional and aesthetic point of view, and their fixed nature contributes positively to a significant increase in the patient's self-confidence but also in the well-being by promoting a healthy lifestyle. Therefore, it is necessary to understand and analyze the characteristics and influence of materials that currently exist, ensuring their perpetuity and bio-integration. The osseointegration of an implant depends on the biocompatibility of the material and its inherent properties (chemical, physical and structural), with the cellular response and biofilm bone healing, at the implant-bone interface. This work intends to develop new multifunctional dental implant, with superior osteointegration capacity, and simultaneously with antibacterial activity. The multifunctionality required for these implants will be conferred through the development of coatings based on bioglass doped with copper, Cu, that enhance significantly the angiogenesis and also present antibacterial activity. The bioglass used as the basis is the 45S5 Bioglass prepared by melt-quenching technique. This material has caused a revolution in healthcare and it was applied in several clinical applications involving the regeneration of hard tissues in medicine and dentistry. The prepared Cu-doped 45S5 bioglasses were analyzed physically, chemically, and biologically. The incorporation of Cu ions does not show a significant change in the glass structure and does not alter the desirable properties of the bioglass. The in vitro bioactivity tests were conducted by immersion tests in simulated body fluid (SBF). Bacteria of the species Staphylococcus aureus, Streptococcus mutans and Escherichia coli, involved in the formation of the pathogenic biofilm, were used to assess the antibacterial activity of bioglass. The results show that the glasses loaded with copper from 0.25% to 2% inhibit the growth of bacteria without being toxic to mammalian cells.

Resume : Boron phosphide (BP) is a new material for electronic devices, which has attractive characteristics for different applications. It is quite chemically inert, it is resistant to the oxidation at high temperatures, and it has high thermal and mechanical stability. Thus it has a potential to create devices operating in extreme conditions. It was theoretically shown in ref. [1] that BP is one of the most promising binary compounds for creating a transparent conducting p-type coating, since it has an indirect bandgap and a large difference between the energies of the direct (4 eV) and indirect transition (2 eV), which implies low optical losses. Consequently, the use of BP/Si heterojunctions instead of poly-Si/SiOx/Si or (p)a-Si:H/(i)a-Si:H/Si could lead to an increase in short-circuit current. Preliminary work has shown that BP could be p-type doped and that the BP/Si interface exhibits a valence band offset either slightly positive (type I straddling gap heterojunction) or slightly negative (type II staggered gap heterojunction), while having a large conduction band offset, making it an excellent candidate as a selective hole contact, without requiring an additional ITO layer [2]. The growth of BP can be carried out by different methods on different substrates: gas-phase epitaxy on Si, plasma-chemical deposition on Si and ZnS, magnetron sputtering on Si. BP layers also can be grown by plasma enhanced chemical vapor deposition (PECVD). It is a reliable, industrial method, which allows electronic-quality films to be grown at low temperatures over large areas. In this work it is proposed to grow BP films on Si substrate using plasma chemical deposition with two different precursors of boron: trimethylboron (TMB) or diborane (B2H6), and phosphine (PH3) as a precursor of phosphorus. The electro-physical and structural properties of BP/Si heterostructures will be presented. The material properties will be analyzed by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), and by chemical characterization Electron diffraction x-ray spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS), and Raman spectroscopy. References: [1] Varley J.B., Miglio A., Ha V., van Setten M.J., Rignanese G., Hautier G. High-Throughput Design of Non-oxide p-Type Transparent Conducting Materials: Data Mining, Search Strategy, and Identification of Boron Phosphide Chem. Mater. 2017, 29, 6, 2568–2573. [2] King, S.W. Valence Band Offset at a-B:H and a-BP:H/Si Interfaces / S.W. King, M. French, M. Jaehnig, M. Kuhn, G. Xu // ECS J. Solid State Sci. Technol. -2012 - Vol. 1 - p. 250-253.

Resume : Among the III-V materials, gallium phosphide (GaP) has gained wide popularity finding application in devices such as LED, Hall sensors, optical filters and solar cells. The current interest of using GaP in solar cells is confirmed by the results of computer simulations. It has been shown that GaP has an advantage over other semiconductor materials when used as a thin transparent emitter. The scientific community is actively working on the formation of solar cells based on GaP obtained by epitaxial methods. However, solar energy applications require affordable and easy scalable deposition technology. One of such technologies is low temperature plasma-enhanced atomic layer deposition (PE-ALD), which makes it possible to obtain high-quality thin layers of binary compounds. Deposition of functional materials by the PEALD method has gained increasing popularity in recent years. One of the main advantages of this method is to obtain thin layers of material with high uniformity, which opens up prospects for depositing on developed structures. We have previously demonstrated a possibility to obtain a thin epitaxial GaP layer on the planar Si wafer using PEALD approach at low temperature (below 400°C). If solar cells are manufactured using flat silicon wafers, they have a high reflection coefficient, leading to reflection of light especially at high angle of incidence. To reduce the amount of reflected light from solar cells, a textured surface of the substrates is required. It is known that the larger the aspect ratio (height/width) in the texture, the less will be the reflection loss and the higher the resulting efficiency of the solar cell. In addition, textured Si substrates can provide current matching in the double-junction systems. This is possible due to enhanced absorption in the p-i-n structure due to a significant increase in the effective area compared to planar structures. Commonly, Si texturing is carried out using wet chemical etching, which does not allow obtaining structures with a high aspect ratio. To form a developed surface with a desired geometry it is proposed to use the cryogenic dry etching. This method makes it possible to obtain a self-organized highly developed Si surface, better known as «black silicon». Reflection from such surface is very low even at high angles of incidence, which is certainly an advantage compared to structures obtained by wet etching. In this work, it is proposed to combine the advantages of cryogenic Si etching for the formation of a developed surface with uniform and conformal deposition of GaP using PEALD method. It is of interest to study the effect of deposition conditions on the uniformity and structure of the resulting layers on a textured Si surface with a high aspect ratio. The structure and composition of the layers were characterized by high resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX).

Resume : Silicon thin film technology (solar cells and flat panel displays) has been driven by hydrogenated amorphous and microcrystalline silicon thin films which are routinely produced using silane plasmas. The dissociation of silane gas molecules results in a wide variety of film precursors, ranging from SiHx radicals to ions and clusters. While SiH3 is often considered to be the main radical for the obtaining of such films, we have shown that changing the process to conditions where silicon clusters and nanocrystals are produced in the plasma can lead to high deposition rates and materials with improved electronic properties, such as hydrogenated polymorphous silicon and polycrystalline silicon [1]. Moreover, by changing the substrate from glass to crystalline silicon and the film precursors from SiHx radicals to silicon clusters, it is possible to produce epitaxial silicon films developing a fragile (porous) interface layer, which favors their transfer to foreign substrates to make ultrathin crystalline silicon solar cells [2,3]. Even more interesting, this low temperature epitaxial process can be extended to doped films as well as to germanium and SiGe alloys and their heteroepitaxial growth on GaAs [4], thus providing an easy route for the integration of c-Si and III-V materials. Last but not least, combining PECVD with low melting temperature metal nanoparticles such as indium and tin, opens the way to the growth of nanowires (including Ge, Si and GeSn), which allow to achieve efficient light trapping and carrier collection in radial junction solar cells on flexible and light weight substrates [5] or even to growth in-plane c-Si nanowires for stretchable electronics and photonics applications [6,7]. 1) Ka-Hyun Kim et.al. Sci. Reports 7, (2017) 40553. 2) R. Cariou et. al. Prog. in Phot.: Research and Applications 24 (2016) 1075-1084. 3) A. Gaucher et. al. Nano Letters 16 (2016) 5358. 4) Gwenaëlle Hamon, et.al. J. Photon. Energy 7 (2017) 022504. 5) X. Sun, et.al. Nano Energy 53 (2018) 83-90. 6) Ruiling Gong et. al. Phys Status Solidi RRL (2021) 2100554 7) Ying Sun et. al. Adv. Mater. (2019) 1903945

Resume : In the last years, Transparent Photovoltaics (TPV) is receiving increasing interest in the development of transparent and semi-transparent systems as smart widows in BIPV applications and as functional devices powering sensors and IoT devices. State of the art TPV devices are mainly based on the selective absorption of the UV and IR spectral regions. Looking into the inorganic materials used for UV-selective absorption, ZnO and Zn(O,S) are basically the most studied inorganic wide-bandgap absorbers, but efficiencies lie below PCE=0.5% so far. As an alternative to increasing these PCE values, other wide-bandgap materials such as a-Si:H could be used but making them ultrathin. The nanometric nature of the a-Si:H absorber allows for a frustrated absorption of longer wavelengths (i.e. green/red/IR regions). Herein, we report on the synthesis and characterization of a-Si:H/oxide semi-transparent devices based on a nanometric absorber while using oxide-based charge transport layers (CTLs) and transparent electrical contacts. Characterization by J-V-T, EQE, UV-VIS, PDS, SEM and XPS are ongoing. Devices have been fabricated with a thickness of <=30nm for the a-Si:H absorber. After an initial screening of materials as CTLs, a first optimized device design using a 75 nm AZO layer as electron transport layer and a 10 nm MoO3 layer as hole transport layer has allowed achieving a promising record PCE of 1.9%, with average visible transparency > 30%. Results of the best devices and their in-depth characterization will be presented. Further optimization of the device efficiency will be discussed by the introduction of nanometric passivation layers and more detailed optimization of the CTLs

Resume : The replacement of fossil fuels with renewable energy sources such as solar is of great importance nowadays.[1] Generally, there are two routes for harvesting solar energy: the photovoltaic and the photothermal processes. More and more applications are driven by the photothermal process, including electricity generation, steam sterilization, and fuel production.[2] Photothermal materials, or absorbers, must strongly absorb the sunlight, while ideally losing little heat to the environment via convection and radiation mechanisms. Therefore, an absorber, that has strong solar absorptance and low infrared emittance, is called a spectrally selective absorber.[3] Cermet coatings have been extensively investigated as selective absorbers due to their high solar absorptance, low IR emittance, and good thermal stability. A cermet is a metal-dielectric composite in which metal NPs are embedded in an oxide, nitride, or oxynitride dielectric matrix.[4] Many parameters impact the performance of the cermet as a solar absorber such as the coating thickness, constituents, and metal NPs volume fraction in the matrix, as well as particle size, shape, and orientation.[4] Alumina-based cermet coatings which have excellent optical properties and thermal stabilities have been extensively investigated as spectrally selective absorbers. The inclusion of silver NPs in the alumina matrix reports the lowest emittance in IR compared to other NPs materials such as nickel or molybdenum. Moreover, the efficiency of the material has been demonstrated to be dependent on the fabrication process. For example, physical deposition leads to a lower thermal emittance compared to electroplating.[4] In this study, we report on the synthesis of a Al2O3-Ag cermet by co-sputtering of a silver and aluminum target in an Ar/O2 gas mixture. The influence of different sputtering parameters on the morphology and optical properties is reported by the mean of scanning electron microscopy and reflectance measurements, respectively. Moreover, the photothermal property of the cermet has been evaluated by measuring the surface elevation temperature under a solar simulator. Our data reveal that by tuning each deposition parameter, one can reach a temperature elevation of the surface up to 8 ͦC after 10 min under 1 sun illumination. We also report the stability of the cermet film without modification of the photothermal property after annealing at 250 ͦC during 1h under air. [1] P.M. Boffey, Science, 1970, 168, 1554–1559. [2] C. Chen et al., Joule, 2019, 3, 683–718. [3] H. Liu et al., Adv. Energy Mater. 2019, 9, 1900310. [4] F. Cao et al., Energy Environ. Sci., 2014, 7, 1615–1627.

Resume : Improving the performance of concentrated solar power technologies (CSP) requires the development of optically efficient and thermally stable absorbing materials. To achieve this, our objective is to develop spectrally selective coatings using plasma technology, i.e., absorbing in the visible and near infrared solar range and with low infrared emissivity. These coatings must also be resistant to high temperatures in air and high thermomechanical stresses. Suitable solutions include ceramic-metal composites (cermets) based on tungsten and SiCH materials. Anti-reflective materials such as TaO_x N_y can be deposited on these cermets to ensure maximum solar transmission to the absorbing part and potentially high temperature protection under oxidizing atmosphere. First, the thermo-optical properties of cermets consisting in tungsten inclusions embedded in SiCH matrix were simulated and optimized by optical modelling, using optical indices measured by ellipsometry on W and SiCH coatings previously developed at PROMES-CNRS. This study revealed that W-SiCH composites exhibit high efficiency in converting concentrated solar flux into heat under CSP working conditions. Then, W-SiCH materials were synthesized by radio frequency reactive PVD magnetron sputtering with ECR microwave assistance, and characterized by SEM, EDS, RBS, spectroscopic ellipsometry and spectrophotometry. In addition, TaO_x N_y deposited by the same method (without microwave assistance) have shown an antireflective potential for W-SiCH absorbing layers due to their suitable optical properties (n ~ 2 at 2 eV). Finally, the thermo-optical performance of W/W-SiC:H/TaON multinanolayer solar selective absorber coatings was simulated based on the experimental optical indices of these materials. As an example, α_s=0.69 and ε(500°C)=0.027 could be obtained with TaO_2,40 N_0,69 and W-SiCH annealed at 500 °C, showing good potential for CSP applications.

Resume : CO2 conversion has been proposed as a potential way to close the carbon cycle and generate chemical fuels. The electrocatalytic reduction of carbon dioxide, powered by renewable electricity, to produce valuable fuels and feedstocks provides a sustainable and carbon-neutral approach to the storage of energy produced by intermittent renewable sources. The development of such a technology is currently hampered by the lack of catalysts, which can drive the reaction at industrially relevant current densities with high efficiency and selectivity. Examples of strategies for optimizing the CO2RR performance include alloying, surface doping, ligand modification, and interface engineering. Our investigations focus on exploring the role of functionalization on the catalytic activity of Cu towards the conversion of CO2 to hydrocarbon products. We developed a method to modify the surface of bimetallic silver-copper (Ag-Cu) catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C2+ species such as ethanol and ethylene and enhances the reaction rates on the surface of the catalyst. As a result, we achieve a maximum Faradaic efficiency for the formation of C2+ of ≈ 80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm-2 for C2+ using functionalized Ag-Cu electrodes, compared to only 33.8% and 70.6 mA cm-2 for the pristine Ag-Cu electrodes. We anticipate that our strategy can further be extended in order to improve the selectivity of the reaction towards the production of specific multicarbon molecules.

Resume : CrSi2 (chromium (di)silicide) is a potential thermoelectric material that has attracted attention in the last few years due to its semiconductor properties and high thermal stability. In this sense, the ion implantation technique can be used to tailor the physical properties of different materials, and enhance their semiconductor and/or thermoelectric performance. This work investigates the influence of different ion species and implantation conditions on the microstructure, electrical resistivity q and thermal conductivity j behaviors in amorphous CrSi2 thin films. ~ 260-nm-thick CrSi2 films were produced by magnetron sputtering and deposited onto a SiO2/Si substrate. Samples were implanted at room temperature and at 250 ºC either with Ne or Al ions to form a concentration–depth plateau reaching a concentration of ≈1.0 at.% (Ne), or ≈0.008 at.% (Al). The microstructural modifications were characterized via TEM and STEM-EDX. The electrical resistivity was measured by the van der Pauw method, and the thermal conductivity measurements were obtained with SThM. The results obtained show that room temperature Al and Ne implantations cause the reduction of the electrical resistivity as compared to the pristine film. In contrast, the electrical resistivity values are significantly higher for Ne and Al implantations in heated substrates. A reduction in the thermal conductivity is observed for all implanted samples when compared to the pristine sample. The microstructure evolution, electrical and thermal behaviors are discussed considering the effects of radiation damage and the formation of dense nanocrystallite arrays during the implantation process.

Resume : Doping is one of the most important techniques in the semiconductor devices process. We have reported epitaxial Si films were grown by means of sputter epitaxy method at relatively low temperature [1]. Lowering the growth temperature is effective in suppressing diffusion. In this study, we investigated the electrical properties and dopant profiles in phosphorus-doped n-type Si films formed by the sputter epitaxy method. Phosphorus-doped silicon films were formed on p-type Si (100) substrates by means of the sputter epitaxy method. The growth temperature was in the range of 189 to 448 °C. The sputtering gas was Ar. The electron density and mobility were measured using Hall effect measurement, and the phosphorus profile was estimated by secondary ion mass spectrometry. The dopant was activated at a growth temperature of 247 °C or higher. The electron density was 1.4×10^19 cm^-3 at this temperature, and the higher growth temperature, the higher the carrier density was and was reached the highest value of 3.6×10^19 cm^-3 at 448 °C. The phosphorus density of the sample grown at 448 °C was 4.6×10^19 cm^-3, so the carrier activation rate was 77% without post-annealing. In contrast, post-annealing is required after the ion implantation at the temperature of 800 to 900 °C or even higher. Furthermore, the density of phosphorus dopants in the none-doped layer under the n-Si layer was decreased exponentially with the slope of 5 nm/decade, which was steeper than that in the film formed by the chemical vapor deposition (CVD) [2]. In this study, phosphorus-doped silicon epitaxial films were formed by the sputter epitaxy method. The carrier activation rate was 77% at 448 °C, and the diffusion of phosphorus dopants was low compared with the film formed by CVD. Refs. [1] K. Ikeno et al., ISPlasma2021/IC-PLANTS 2021, 1165 (2021). [2] Chen Li et al, Nanoscale Res Lett, 15, 225, (2020). The work was partly carried out in the Advanced ICT Devices Lab at NICT.