Carbon-, or nitrogen-containing nanostructured thin films

Resume : Research fields are commonly congregated around key physical and chemical properties, but often correlative approaches are lacking. An example can be found in the field of hard and protective coatings. Mechanical properties are central, but many other features, such as thermal management, could be detrimental in applications. Here, we discuss density functional theory (DFT) aspects of two isostructural nitrides: TiAlN and NbON (prototype NaCl). Besides considering hardness, a design methodology for hard coatings must include additional physical and chemical properties, such as thermal conductivity. Recently, also the hard coating – environment (or workpiece) and hard coating – substrate interfaces have been described, constituting new research directions. In the case of TiAlN, DFT enabled atomic scale understanding of the phase stability, formation of defect structures and interfaces for the elastic properties, enhancement of toughness, initial stages of oxidation, and interaction with molten polymers and metals. The second nitride coating discussed here, NbON, is a promising thermoelectric phase. Even though transport properties are central in designing efficient thermoelectrics, mechanical properties should also be considered to minimize their thermal fatigue during multiple heating/cooling cycles. Thermoelectric NbON was designed by filling the vacant sites in NbO with N, thereby increasing fivefold its Seebeck coefficient. Based on the elastic response, NbON can be perceived as ductile, which is validated experimentally. Only by applying holistic approach, where correlative treatment of many properties and phenomena occurring at different scales ranging from nanoscale to continuum, it is possible to design novel materials for specific applications.

Resume : Concerns regarding pollution prevention have rushed incentives for the advancement of solid lubrication to replace, whenever possible, oils and other liquid lubricants. Self-lubricant nitride coating systems with release of the lubricous species have enormous potential to be used in the protection of surfaces of components working in extreme conditions of wear. However, the rapid release of the lubricious agent and consequently, its total depletion from the coating has delayed the transfer of these coatings to the industry. This work is focused on the development of a new class of thin films with capacity to control the lubricious metal release. Thus, the effect of V additions on the structure, mechanical properties and tribological behaviour of Ti-Si-N films with nanocomposite structure, deposited by high power impulse magnetron sputtering (HiPIMS) in deep oscillation mode (DOMS) using different peak powers is investigated in this research. The TiSiN system was selected as matrix, because if deposited as a nanocomposite structure, the SiN phase, in the grain boundaries, will work as an anti-diffusion barrier to the lubricious metal ions diffusion. V additions shift the diffraction peaks to higher angles, suggesting the formation of a substitutional solid solution. Coatings deposited at lower peak power displayed a [111] preferred orientation and columnar morphology, ascribed to both the low energy bombardment conditions and low N2 dissociation rate. A [200] preferential orientation and a compact morphology was produced at high peak power. V additions decreased both friction coefficient and wear rate of the coatings, independently of the peak power used, due to the formation of a lubricious V2O5.

Resume : The phase composition and resulting microstructure of PVD hard coating materials such as TiAlN and CrAlN are crucial for their industrial applications [1]. In situ X-ray experiments are a versatile tool to study the microstructure formation during deposition [2]. Here, we present first results of a combined in situ X-ray reflectivity (XRR) and X-ray diffraction (XRD) study during reactive magnetron sputtering of Cr-Al-N coatings on Silicon. The experiments were performed at the MPI beamline of the synchrotron radiation source ANKA (Karlsruhe, Germany). The coatings were deposited by co-deposition, using rf magnetron sputtering for the Aluminum target and dc magnetron sputtering for the Chromium target. The target powers and the Ar/N2 flux ratio were varied, thus controlling the chemical composition and the reactive sputter regime. The combined results of simultaneous in situ measurements reveal a composition-dependent change in the structure formation, from rough, crystalline fcc layers at low Al content to smooth, amorphous layers at high Al content, which can already be identified during the initial growth stages. Furthermore, the real-time monitoring links instant signal (i.e. microstructure) changes with instabilities of the sputter process, offering thus new perspectives for the development of reactive sputter processes. [1] F. Rovere et al., Appl. Phys. D: Appl. Phys. 43 (2010) 035302, [2] M. Kaufholz et al., Journal of Synchrotron Radiation, 2015, 22, 76-85

Resume : Nitriding is a well-known surface modification to enhance wear resistance of metallic materials. The formation of nitriding layer is well described for conventional microcrystalline materials. However, with the development of their nanostructured counterparts, the question arises how the nanostructure influences the nitriding process. To answer this question, a series of experiments have been designed to compare the formation of nitriding layers in an austenitic stainless steel. To refine the microstructure down to nanoscale, hot (at 1000°C) and room temperature (RT) hydrostatic extrusion (HE) was applied to austenitic stainless steel 316LVM with a total true strain of 1.4. Subsequently, samples were nitrided using low-temperature plasma-assisted nitriding at 430°C for 1h, 3h and 5h. Annealed samples with coarse grains of 30 mikrometers in diameter were used as reference samples. In hot HE samples, most of the microstructure is occupied by cell structures with cell walls consisting of dislocation tangles. In HE samples, on cross sections one can distinguish twins of various width and shear bands. After nitriding the thickness of nitrided layers was measured. The phase composition of layers were investigated by X-rays diffraction. Furthermore, mechanical properties were evaluated in nanohardness tests.

Resume : The Modified Embedded Atom Method (MEAM) interatomic potential is used within the classical Molecular Dynamics (MD) framework to perform simulations of important model materials such as TiN, in order to understand the processes which control TiN growth modes on a fundamental level. We report the results of large-scale simulations of TiN/TiN(001) deposition using a TiN MEAM parameterization which reproduces experimentally-observed surface diffusion trends, correctly accounts for Ehrlich barriers at island step edges, and has been shown to give results in good qualitative and quantitative agreement with Ab Initio MD based on Density Functional Theory. We deposit 85% of a monolayer of TiN on 100x100 atom TiN(001) substrates maintained at 1200 K, at a rate of 1 Ti atom per 50 ps, for total simulation times of 212.5 ns. We use N/Ti flux ratios of 1, 2, and 4, and incident N energies of 2 and 10 eV, to probe the effects of N2 partial pressure on TiN(001) growth modes. We observe nucleation of TixNy molecules; N2 desorption; formation, growth and coalescence of mixed <100>, <110>, and <111> faceted islands; as well as intra- and interlayer mass transport mechanisms. For N/Ti flux ratios of 1 at 2 eV incidence energy, films exhibit Ti-rich surface regions which serve as traps to nucleate higher layers, leading to multilayer growth. Increasing the N/Ti flux ratio shifts the growth mode to layer-by-layer and modifies the overall film composition from under- to over-stoichiometric. As the N content of films is increased, N-terminated <110>-oriented island edges become increasingly dominant and the substrate vacancy concentration changes from being N- to Ti-dominated. We discuss the implications of these results on thin film growth and process tailoring.

Resume : SiCN:H thin films are widely used for their mechanical, optical and electrical properties. These coatings can be produced by different deposition techniques, leading to nitride and carbide like materials. In this study, SiCN:H thin films are deposited by three different plasma processes : - Microwave PECVD coaxial using tetramethylsilane (TMS) precursor diluted in Ar/NH3 gas mixture (PROMES laboratory), - ECR PECVD using H2/Ar/Hexamethyldisilazane (IJL Institute), - Radiofrequency Reactive Magnetron Sputtering using a silicon target in Ar/N2/CH4 (ICCF institute). Film atomic composition and arrangement determined by FTIR and XPS reveal that deposited layers can be tuned from nitride to carbide. Si-N and Si-C bonds quantification has been used to account for the chemical environment of both types of materials. Film optical properties have been successfully determined using spectroscopic UV-Visible ellipsometry. Refractive index (n) and Tauc’s optical gap (Eg) are modified over a wide range of values (1.6 ≤ n ≤ 2.5 and 0.25 ≤ Eg ≤ 3.5 eV) with nitrogen addition, leading to the general trends of both type of SiC or Si3N4 materials. The evolution of the film properties as a function of the deposition time is also investigated. This work is supported by the French National Research Agency (HD-Plasm-A-SiNOC:H project: PROMES/ICCF/IMN/IJL french laboratories).

Resume : Recently, organic materials have been intensively investigated in solar cells (SCs) with the aim of replacing conventional semiconductor devices thanks to their lightweight and potential low production cost. Significant improvements in energy conversion efficiency of these devices have been realized (reaching 11% [1] ) but their performance is still not sufficiently good enough for a large production scale. Among the recent progress in the SC study, the use of the organic-inorganic hybrid perovskites as absorbers has been demonstrated to provide higher efficiency and stability for applications in photovoltaics. The improvement of the cell performance with a power conversion efficiency reaching 20 %, is thought to be linked to their optoelectrornic properties of perovskites: strong optical absorption, high carrier mobility and diffusion length. However, from the defect point of view, the complex structure of the materials is prone to formation of defects, which enables charge carrier trapping, and therefore can impact on the long term stability and electrical property of the solar cells. In this talk, we briefly review some fundamental aspects of organic-inorganic hybrid perovskites and their applications in solar cells. In particular, we shall present and discuss updated results on the investigations of defects in solar cells using this material as an absorber. Understanding the structure-property relationships of perovskites may help to improve the design and thus, the performance of hybrid organic-inorganic solar cells. [1] C. Chen, W. Chang, K. Yoshimura, K. Ohya, J. You, J, Gao, Z. Hong, Y. Yang Adv. Mater. 26 (2014) 5670–5676

Resume : The search of new materials for solar absorbers is a challenging task. Among the various criteria to be fulfilled, environmental aspects are very important. These materials have to contain abundant and non-toxic elements. Very recently, it has been shown that ZnSnN2 is a promising n-type material for photovoltaic applications. Since this nitride has been scarcely studied, it is necessary to continue research activities to optimize its functional properties. This communication aims to compare two deposition methods: reactive co-sputtering of two metallic targets and reactive sputtering of an alloyed Zn-Sn target. Whatever the deposition process, the targets have been sputtered by regulating the target voltage. Due to the low melting point of tin, the voltage applied to this target is quite low. Then, the deposition rate of ZnSnN2 is limited to approx. 500 nm/h. This limitation can be overcome by sputtering an alloyed target. As-deposited films crystallize in an orthorhombic structure. No structural change can be evidenced after annealing at 400 °C. Mössbauer spectrometry has been used to characterise the tin chemical environment. The use of high nitrogen partial pressure allows the deposition of films without metallic tin contamination. The optical band gap (approx. 2.1 eV) has been deduced from UV-Visible spectroscopy measurements. Finally, the electrical properties of nitride thin films have been measured using the four point probe method.

Resume : Fabrication of organohalide perovskite solar cells based on ZnO naoparticles (NPs) has some advantages such as low-temperature process without sintering. However, there are few reports about perovskite solar cells fabricated on ZnO NPs due to the instability of perovskite on top of ZnO, i.e. the reaction of ZnO with perovskite materials. In this work, we report the details of a decomposition mechanism for CH3NH3PbI3 perovskite materials, and we find that the perovskite materials on top of the ZnO NPs layer will be converted into PbI2 during the annealing process due to the existence of hydroxide groups on the surface of the ZnO NPs. Depending on the annealing temperature, the reaction rate and the quality of the perovskite layer are changed. Herein, we proposed a nanocomposite to solve this problem. We synthesize a quasi core‒shell structure of ZnO/graphene QDs and employ it as an electron transfer layer. In this regard, graphene has two important functions: not only passivates the surface of the ZnO QDs to prevent the reaction but also extracts the charge carriers quickly from the perovskite layer to reduce the carrier recombination. The results of time-resolved photoluminescence measurement (TRPL) and electrochemical impedance spectroscopy (EIS) of perovskite solar cell have demonstrated that graphene decreases the carries life time and charge-transfer resistance due to fast extraction of electrons and its high conductivity, respectively. The PV measurements results show that, a perovskite solar cell using the ZnO/graphene QDs layer exhibits a stable power conversion efficiency as high as 15.2% and 11.2% on FTO glass and Polyethylene terephthalate (PET) substrates under AM1.5G illumination, respectively.

Resume : The need to harvest energy from renewable sources has increased dramatically in the last decades. Research efforts have mainly focused on new materials for solar cells, converting a small proportion of the solar energy into electricity. An alternative energy harvesting approach is provided through solar thermal applications in which sunlight is collected by absorbers that in turn heat a convective medium. Most of the materials currently in use exploit only a part of the solar radiation, leaving a great proportion unexplored. We here report on the synthesis and characterization of hydrogenated amorphous carbon (a-C:H) metal (Ag and Au) nanocomposite films with localized surface plasmon resonance (LSPR) characteristics and enhanced absorption capabilities. Free standing nanoparticles (np) of Ag and Au have been formed by annealing magnetron-sputtered films and have subsequently been capped with a layer of a-C:H. The np size was controlled through deposition time and annealing parameters. On the other hand, the a-C:H layer was deposited through an ion-beam source by cracking methane molecules using an RF plasma source. The morphological characteristics of the nps have been investigated with SEM and AFM whereas optical measurements have been performed using a UV/VIS spectrometer. Roughness, density and thickness of the nanocomposite films have been probed using X-ray reflectivity. The factors that affect the LSPR peak position such as np size, annealing conditions and np’s hosting environment have been investigated and quantified. These synthesis/processing- structure-property relations open up the way for tailoring and optimizing the absorption of nanocomposite films for solar thermal harvesting applications.

Resume : III-nitride and II-VI oxides are wide band gap semiconductors which have unique applications in both opto-electronic and optical devices. They exhibits interesting optical properties that could be applied in quantum confined structures and light emitting devices [1,2]. In this work, we report a chemical technique for synthesis of one dimensional nanostructures in a horizontal three zone furnace with alumina tube. AlN with different morphologies and sizes are grown on different substrates by thermal evaporation of source materials and gas transport in cold zone of furnace using a carrier gas. The effect of substrate, additional metal sputtering, gas flow flux and vacuum conditions are investigated on the structural and morphological studies by means of the field emission SEM, EDX and XRD. Photoluminescence spectra of the nanostructures show high intensity optical emission at room temperature around UV and blue wavelength which is very interested for LED applications. [1] X.W. Sun, J.Z. Huang, J.X. Wang and Z. Xu, Nano Lett. 8 (2008) 1219. [2] A. Khan and M.E. Kordesch, Mater. Res. Soc. Symp. Proc. 872 (2005) 1.

Resume : We present here self assembled growth of InAsN quantum dots (QDs) on GaAs (001) substrates by solid source molecular beam epitaxy (SS-MBE) associated with a radio frequency plasma source for nitrogen incorporation into InAs QDs. These nitride dots along with InAs/GaAs QDs used as a reference have been investigated by high resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM) and photo- luminescence spectroscopy (PL). Nitride QD sample consists of 1.8 ML InAs wetting layer followed by 0.7 ML of InAsN QDs. It has been confirmed by HR-XRD that low nitrogen background pressure (410-6 Torr) with high power (450W) enables lower incorporation of nitrogen (0.6 %) into InAsN dots whereas relatively high pressure (510-6 Torr) ensures 2.2% nitrogen incorporation. PL measurement exhibits higher emission wavelength with much reduced intensity in case of InAsN0.022 QDs than that of InAsN0.006 QDs because of higher nitrogen incorporation. Rapid thermal annealing (RTA) was carried out on the samples in nitrogen ambient for 30 sec and blue shift has been observed upto 800C. For both nitride QDs annealed at 750C, improvement in intensity of the emission peak has been achieved over one hundred fifty times whereas the reference sample provides a negligible enhancement. Hindrance of incorporation of higher nitrogen in InAs QDs can be resolved by this method. DST, IITBNF and Director SAMEER are acknowledged. Key words: SS-MBE, InAsN QDs, RTA, enhancement in PL.

Resume : We have grown InAlN, InAl15N, and InAlN/InAl15N thin films on Si (111) substrates using natural and isotopically enriched nitrogen (15N2) as reactive gases by reactive magnetron sputter epitaxy (MSE) [1]. X-ray diffraction θ-2θ scans confirmed that the targeted composition x = 0.17 of InxAl1-xN film was obtained. High-resolution transmission electron microscopy images show that all InAlN films are wurtzite structure and were grown epitaxially on Si(111) along c-axis orientation, although interlayers, containing amorphous and partially crystalline structures, with thicknesses ranging from 1.2 to 1.5 nm, were formed between the InAlN and the Si substrate. Energy-dispersive x-ray spectroscopy line profile indicate that the interlayer mostly consists of SiNx. However, the d-spacing measurement of the partially crystalline structures implies a co-existence of both SiNx (major) and Al-rich InAlN (minor) nanocrystals formed in the interlayer. From compositional depth profiles using time-of-flight secondary ion mass spectrometry, we further confirm that InAl15N and InAlN/InAl15N films were successfully grown on Si as well. Also here a Si15Nx interlayer was formed between the film and substrate. No prominent interdiffusion between InAlN and InAl15N was observed, indicating a good thermal stability of the formed isotopic nitride. 1. C. L. Hsiao et al., Nano Lett. 15, 294 (2015); E. A. Serban et al., Nanotechnology 26, 215602 (2015); M. Junaid et al., Mater. Sci. Semicond. Proc. 39, 702 (2015).

Resume : We tested graphoepitaxy as a technology to control in-plane orientation of organic semiconductor thin films on amorphous substrates. Such technology is important to improve the performance of organic thin film transistors because the surface of the substrates (gate dielectric) is often amorphous and the orientation of the films becomes random. We made periodic microgrooves on thermally oxidized silicon substrates by electron beam lithography. The surface of the grooved substrate was cleaned by UV/ozone (makes surface hydrophilic), or further treated with hexa-methyl-disiloxane (HMDS) (makes surface hydrophobic). A sexithiophene (6T; C24H14S6) thin film was grown on the grooved substrate by molecular beam deposition. Morphological analysis of crystal grains by atomic force microscopy (AFM) and grazing-incidence x-ray diffraction (GIXD) revealed that in-plain oriented growth (graphoepitaxy), b-axis was parallel to the grooves (c-axis was perpendicular to the grooves) on hydrophilic surface and b-axis was perpendicular to the grooves (c-axis was parallel to the grooves) on hydrophobic surface, was achieved [1]. Such orientation change is probably caused by the interaction between 6T molecules and the molecules terminating the groove surface. In the presentation, I will also show results of molecular dynamics simulation explaining such orientation change which results from surface conditions. [1] S. Ikeda et al., J. Appl. Phys., 103 , 084313 (2008).

Resume : To understand the phase-change mechanism of C doped In-Sb-Te, we fabricated C (1.5 wt.%) doped In-Sb-Te (CIST) thin film with amorphous phase. We observed two electrical-phase-changes at 250 and 275 ℃ in the sheet resistance measurement. All samples at each temperature are characterized by HRXRD, TEM, and HRXPS with synchrotron radiation. In a-CIST, the Sb-C bonding was observed with a kind of metal carbide. In the 1st electrical-phase-change at 250 ℃, the strong Sb-C bonding was formed in the film without structural-phase-change (still amorphous). On the other hand, the 2nd electrical-phase-change at 275 ℃ was due to the structural-phase-change from amorphous to crystalline without the change of chemical state.

Resume : In this work, we investigate the thermal oxidation effect on optical and thermal properties of meso-porous silicon (meso-PS) layers using photoluminescence (PL) and photothermal deflection techniques (PDS, PTD). Samples have been successfully prepared by electrochemical anodization process. After a pre-oxidation for 1h 30 min at 300°C, layers are thermally oxidized in dry oxygen at different temperatures (800, 1000°C) and durations. PL measurements show that the annealed layers have comparable spectra with a peak position focused on 2.1 eV. This behavior indicates the formation of luminescent silicon (Si) nanocrystallites with comparable average sizes. From the effective mass theory, the diameter of those nanocrystallites was estimated to be around 2.2 nm. Another estimation of the mean size of the Si nanocrystallites obtained from the evolution of the thermal conductivity of the meso-PS layers based on photothermal deflection technique (PTD) data was close to the values obtained from the PL results. Photothermal deflection spectroscopy (PDS) measurements show that the thermal oxidation affects the absorption edge of the Si substrate. The optical band gap energy of the started substrates determined from the Tauc’s relation is observed to increase with the thermal temperature and duration.

Resume : In this work, photothermal deflection techniques have been used to characterize the opto-thermal properties of porous GaAs samples. In particular, those layers are formed on heavily doped p-type GaAs substrates using electrochemical anodization process at different current densities (6, 12 and 24 mAcm-2). Photothermal deflection spectroscopy was used to determine the optical absorption spectra and the band gap energy of both porous layer and substrate. An estimation of the average mean size of the GaAs nanocrystals obtained from the effective mass theory and based on photothermal data is of about 8 nm. Spectral Reflectance was employed in the wavelength range of 250 to 800 nm, which served to exclude an important decrease in the optical loss with anodization current density. From the dependence of the photothermal deflection signal on the excitation light modulation frequency, thermal conductivity of the porous layers was evaluated. It was found that the increase of the current density causes a huge decrease in the thermal conductivity of the porous GaAs layers. This reduction is mainly due to phonon boundary scattering at the increased amount of interfaces. The obtained results reveal porous GaAs as an interesting candidate for both thermoelectric and photovoltaic applications in which thermal transport is a crucial issue.

Resume : The present work is dedicated to the complex study of Mo-Si-B-N films produced by direct current magnetron sputtering (DCMS) of multiphase ceramic MoBSi cathodes. Special attention was paid to increasing of adhesion of the films to the different types of substrates. High power impulse magnetron sputtering (HIPIMS) and ion implantation assisted magnetron sputtering (IIAMS) were applied for this reason. The Mo-xB-ySi (x=0-50at%, y=0-67at%) cathodes were manufactured by self-propagation high-temperature synthesis. MS were performed in Ar, N2, and Ar-15%N2 gas mixture. Mo-, Cr-, Ni-based and WC-Co alloys, Al2O3 and Si, C/C and C/SiC composites were used as substrate materials. To evaluate the short- and long-time oxidation resistance, diffusion-barrier properties, and thermal stability, films were isothermally annealed in air atmosphere at temperatures 700-1700C. The structure of the as-deposited and heat-treated films, structure of HIPIMS- and IIAMS-formed pseudodiffusion interlayers were studied by means of XRD, SEM, HR TEM, GDOES, XPS, FTIR, and Raman spectroscopy. The mechanical and tribological properties of the films were measured using Nanohardness-tester and HT-tribometer. Adhesion strength was estimated by scratch-, impact-testing, and thermo-cycling experiments. The results obtained show that Mo-Si-B-N films with optimal structure and phase composition demonstrate hardness up to 35 GPa, elastic recovery up to 70%, elastic modules less than 350 GPa, wear rate less than 2∙10-6 mm3N-1m-1, high oxidation resistance up to 1600C. HIPIMS and IIAMS deposited films exhibited two times higher adhesion strength compared to DCMS samples.

Resume : In this work, we investigate the effects of growth conditions on the optical properties of bulk AlxGa1-xN layers using photoluminescence (PL), time-resolved photoluminescence (TRPL), and photoreflectance (PR) techniques. The studied samples were grown by atmospheric-pressure metal organic vapor phase epitaxy (AP-MOVPE) on GaN templates. Our results show that the Al solid composition (x) of the studied AlxGa1-xN layers is related not only to the trimethylaluminum (TMA) flow rate, but also to the trimethylgallium (TMG) and NH3 flow rates. It is found that the increase of the Al solid composition, via increasing TMA or NH3 flow rates, deteriorates the optical quality of the AlxGa1-xN layers. In contrast, when the TMG flow rate is reduced, the optical quality is improved and the Al composition is increased. Keywords: AlGaN, photoreflectance, photoluminescence, time-resolved photoluminescence, metal organic vapor phase epitaxy.

Resume : In the present work, TiCN, ZrCN and NiCN reference coatings were alloyed with Cr and Si. The alloying elements were selected because Cr and Si additions are known to improve corrosion and oxidation resistance of transition metals based hard coatings. TiCrSiCN, ZrCrSiCN and NiCrSiCN coatings have been deposited on Si and 316 L steel substrates by cathodic arc method in C2H2 N2 reactive atmosphere. Film characterization was performed in terms of elemental and phase composition, hardness, adhesion, corrosion resistance, friction and wear performance in 3.5% NaCl solution. It was found that the coatings were composed of nanoscale carbonitride crystallites (grain size 3.8‒9.6 nm) embedded in an amorphous hydrogenated carbonitride phase. Hardness and adhesion related critical load values in the ranges of 24-35 GPa and 27-35 N, respectively, were measured. The experimental results revealed that Cr and Si incorporation into the reference coatings resulted in enhanced corrosion resistance, more electropositive corrosion potential, lower corrosion current density and higher polarization resistances being measured. Compared to the reference coatings the alloyed coatings exhibited superior tribological behavior.

Resume : Microlenses are widely used in mobile phones, digital projectors, light emitting diodes, etc. In this work, the plano-convex microlenses with nominal diameter of 16 – 28 µm were fabricated on a fused silica substrate in two ways: by dose modulated 3D electron beam lithography and optical lithography followed by thermal reflow technique. Surface wettability was varied using plasma treatment and ion beam deposition of diamond like carbon (DLC) techniques in order to find the optimal thermal reflow conditions. We found that resulting shape of the microlenses is strongly dependent on the surface treatment conditions and the best results were obtained for microlens arrays on DLC and SiOx doped DLC coated substrates. The nominal 3D exposure dose determined a fidelity of microlenses after thermal reflow. Minimal temperature required to complete reflow of the lenses on SiOx doped DLC coated fused silica substrates depended on the lateral dimensions of the lenses and varied from 130 C to 140 C. Radius of curvature for the fabricated lenses could be tailored by the further increase of reflow temperature.

Resume : The dependence of structure stability, surface effects and elastics properties of free nc-TiN nanocrystals on a size in the range of 1 – 20 nm was investigated by means of molecular dynamics and statics using the LAMMPS code. The nanocrystals were presented as polyhedral particles with two different types of the surface morphology, the quantity of Ti ions being equal to N ones. The structure stability of nc-TiN was determined by the absence of negative frequencies in the vibration spectrum at temperature 373 K. The simulation showed both the absence of negative frequencies for the sizes of particles in the chosen range and the highest wavelength restriction associated with finite size of the particle. It has been revealed that the surface tension coefficient depends on the surface morphology and is described by a cubic polynomial function of the size. According to the obtained results the surface tension coefficient is mainly determined by a surface pressure which was calculated as a level of stress state of the particle after the energy minimization. The highest value of the surface tension coefficient equals 671 mJ/cm2 for the nc-TiN with a diameter of 10.8 nm. The surface pressure changes the sign and the surface tension coefficient becomes negative with increasing in the particle dimension more that 20 nm. It results from the intention of the crystal to increase the free surface, the elastic module of the nc-TiN being close to the same module of the bulk material.

Resume : Nanocomposites consisting of transition metals nitrides nc-MeN (Me=Ti, Zr, V etc.) nanocrystals with a size of 3 – 4 nm separated by some monolayers of amorphous silicon nitride Si3N4 are reported to possess high hardness, high elastic recovery and thermal stability in a wide temperature range. The purpose of the present work is a determination of the initial defect structure of nc-TiN/a-Si3N4 nanocomposite, stress fields in the amorphous matrix, interphase boundaries and the nanocrystals and its dependence on a size and volume fraction of the nc-TiN particles. The defect structure of nc-TiN/a-Si3N4 nanocomposite results from mismatch defects. The nc-TiN/a-Si3N4 nanocomposite was modeled as a cubic object with an edge length of 1.5 – 1.9 nm including polyhedral nanoparticles of nc-TiN with the size of 1.0 – 1.5 nm surrounding by amorphous matrix a-Si3N4 with the total number of 500 – 600 atoms. The simulation was carried out with the high-performance computational cluster Cyberia (Tomsk, Russia) using the calculation of the ground state, structural optimization and ab-initio molecular dynamics implemented in the QuantumEspresso code. The electron density, the function of electrons location, density of states and stress were determined for the structure analysis. The obtained results were compared with literature data.

Resume : The study introduces a quite innovative way for the synthesis of functional films onto substrates directly from the liquid phase. The reported method is based on the initialization of the synthesis by means of an atmospheric pressure plasma jet operating with argon above a thin liquid film of the organic compound. The plasma initiated synthesis and annealing is demonstrated using three liquids: hexamethyldisiloxane (HMDSO), octamethyltetrasiloxane (OMCTS), and tetrakis(trimethylsilyloxy)silane (TTMS) [1]. The process is initiated by the formation of a thin SiOx layer at the interface between liquid and plasma by precursor activation and successive cross-linking of the molecular complexes inside the liquid. The resulting film has been investigated with in-situ ATR-FTIR spectroscopy (deposition directly on the diamond crystal) and characterized by high resolution SEM imaging methods at low energies of the electron beam. The experimental and theoretical approach related to imaging of specimens with electrons of energy below 100 eV is investigated in HV and UHV SEMs in reflected detection mode. The chemical composition of the SiOxCy films is obtained by XPS analysis. The deposited films exhibit a low concentration of carbon groups in the films and more generally a surprisingly high degree of chemical similarity. [1] J. Schäfer et al, Surf. Coat. Tech. (in press), DOI: 10.1016/j.surfcoat.2015.09.047

Resume : In machining applications like milling or turning, frequently hard coatings are applied to increase the performance of the used tools. The positive effect of coatings on tool performance is typically attributed to their high hardness, low friction coefficients against common workpiece materials as well as to improved oxidation resistance. The influence of the thermal conductivity is usually neglected, although adequate thermal shielding of the substrate material can retard or even prevent plastic deformation of the tool and consequently, also the accompanying damage. In particular, hard coatings consisting of metastable solid solutions deposited by PVD techniques, like TiAlN or CrAlN based coatings, are reported to exhibit low thermal conductivities in the as deposited state. Due to their metastable nature, the micro- and nano-structure and phase composition of such coatings changes during annealing which also affects the thermal conductivity. Within this work, the thermal stability and micro/nanostructural evolution of metastable TiAlN and CrAlN hard coatings and the effect of annealing on the thermal conductivity were investigated. As reference, the results were supplemented by measurements on TiN, CrN and AlN coatings. The thermal stability of the metastable coatings was investigated by differential scanning calorimetry (DSC) and thermo-gravimetric measurements, giving information on temperatures where spinodal decomposition, phase transformation and mass-loss or -gain due to chemical reactions occur. Thus, suitable temperatures for subsequent isothermal vacuum annealing treatments could be selected. The micro- and nanostructure of the as deposited and annealed coatings was investigated by X-ray diffraction and the thermal conductivity of the coatings was determined using time-domain thermoreflectance. The obtained results indicate in general an increasing thermal conductivity with increasing annealing temperature, which can be attributed to spinodal decomposition and phase transformations. However, besides the significant influence of the micro- and nanostructure on the thermal conductivity of the as deposited coatings, it was found that the initial microstructure, can alleviate or even prevent the increase of the thermal conductivity during isothermal annealing. The presented examples highlight the benefits of modern hard coatings and sophisticated heat-treatment strategies for a knowledge based thermo-physical design.

Resume : The dependence of carrier effective mass of GaNxAs1-x, InNxP1-x, InNxAs1-x, and InNxSb1-x alloys on nitrogen content is theoretically investigated using a 10-band k.p model. The electron effective mass m*e at the bottom of conduction band in GaNxAs1-x and InNxP1-x exhibits a gradual increase as a function of N concentration in the range 0-1% and a decrease for x between 1 and 5 %. However, the behavior of m*e in InNxAs1-x and InNxSb1-x shows a strongly decrease in all studied x-range. Our theoretical results are compared with the available data reported in the literature. On the other hand, contrary to heavy-hole effective mass m*hh, the light-hole effective mass m*lh in all studied alloys is significantly affected by nitrogen states which modify the non-parabolicity of the LH band. The modification of the carrier effective mass affects the transport and mobility properties of the III-N-V alloys. Keywords: Diluted III-N-V alloys; 10-band k.p model; carrier effective mass. * Corresponding author: ahmed.rebey@fsm.rnu.tn

Resume : Plasma spray coating technology and deposition is one of the most important technologies available for producing the high-performance surfaces required by modern industry. In plasma spray coating process, particles are fed into a high- velocity, high- temperature gas jet where they melt or partially melt while being propelled at high velocity onto the surface to be coated. The flattening characteristics of the droplets impinging on a substrate are important determinants in governing the eventual quality of the plasma spray coating. Since plasma spray equipment is expensive to operate, the cost of developing new coatings can be very high. A computer model capable of predicting the coating properties as a function of process parameters will greatly reduce the development time and cost. Different codes have been developed in recent years to simulate the overall thermal spraying process, as well as the growth of the 3D coatings. The present investigation was carried out to have an approach to systematize the atmospheric plasma spraying process of two molten droplets in order to create a basis for numerically modeling the plasma dynamics, Keys words: Plasma spray process; molten ceramic; coating properties; fluid dynamic technique.

Resume : The objective of this work has been to study the structural and mechanical properties of amorphous SiC:N thin films. The a-SiC:N films were grown by plasma-enhanced chemical vapor deposition (PECDV), using Hexamethyldisilazane (HDMSN) as precursor on 316L stainless steel and crystalline silicon substrates <100>. For the deposition, the changed parameters were the self-bias (from -150V to -450v) and the deposition temperature (25oC, 200oC and 300oC) The deposition rate and the internal stress of the films were obtained by profilometer. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy used to identify the presence of bonding between Silicon, Carbon and Nitrogen atoms. The chemical composition of the surface was determined by XPS. The chemical composition of the bulk and the interface between the substrates and the films were determined by Glow Discharge Optical Emission spectroscopy (GD-OES). The results show higher concentration of Si and C in the interface between stainless steel and a-SiC:N films. Raman spectroscopy was employed to observe the presence of the D and G bands with characteristics of nanostructured carbon films. Atomic force microscopy (AFM) evidenced the presence of nanostructures on the surface of the films. The nanoindentation analysis determined that the hardness of the films are between 8 and 12 GPa.

Resume : Contrary to Fe, Co or Cu nitrides, the Ni ones are scarcely studied. Thus, the binary Ni-N system is not well defined. It contains a stable hexagonal phase that exhibits a Ni3N formula. Although another nitride (Ni2N) has been also reported, the structure and the properties of this material are not clearly detailed in the literature. Nickel nitride thin films have been deposited at room temperature on glass and silicon substrates by reactive sputtering of a Ni target in various Ar-N2 atmospheres. The increase of the N2 partial pressure allows the deposition of either pure Ni3N or Ni2N films. Biphased films can be also deposited with the use of a N2 flow rate ranging between those necessary to deposit single phase. Electron probe microanalysis has been used to determine the Ni / N atomic ratio in as-deposited films. Ni2N films exhibit a preferential orientation in the [110] direction. Cumulative X-ray diffractogram obtained at various chi angles has been used to show that Ni2N crystallizes with a primitive tetragonal unit cell. Full profile refinement using a Rietveld method confirmed the atomic arrangement proposed by ab initio calculation. Ni2N films have been annealed from 100 to 300 °C. XRD analyses of films annealed at 100 and 150 °C show a slight shift of the Ni2N (110) diffraction peak position due to a progressive denitridation. In addition to Ni2N, Ni3N is evidenced after annealing at 200 and 250 °C. Finally, metallic nickel is observed after annealing at 300 °C.

Resume : Synthesis of carbonitride thin films containing high percentages of nitrogen and their characterization has some interest with respect to potential applications in hard coatings, optics, optoelectronics. In another field of research, carbonitride particles are produced in the CH4-N2 planetary atmospheres of the outer Solar system, such as the atmosphere of Titan and Pluto. Taking benefit of the Optimist instrument from the CNRS Cold Plasma Network (Réseau des Plasmas Froids), we could synthesize CNx films in CH4-N2 plasmas at substrate temperatures from -180°C to 25°C, and achieve in situ XPS surface characterization at synthesis temperature and during warm-up to room temperature. Process parameters investigated are the gas mixture (5-100% CH4 in N2), total pressure (2 and 10 Pa) and substrate temperature. Film deposited at room temperature present a composition (N/C) varying from 0 (100%CH4) to 1 (5% CH4). Subsequent ex situ analyses were carried out by high resolution XPS, FTIR and ellipsometry. FTIR and XPS show in particular the presence of C(sp2)-N, N-C(sp2)-N, C(sp2)=N and nitrile groups. During warm-up of the sample under vacuum we observed a strong pressure increase revealing outgassing of the thin film. Mass spectrometry analysis and vapour pressure data allowed identifying that ammonia and cyanides are the main chemical compounds outgassing from the film; and evolution of the C1s and N1s XPS spectra is consistent with this interpretation.

Resume : Enhanced toughness in hard and superhard thin films is a primary requirement for present day ceramic hard coatings, known to be prone to brittle failure during in-use conditions, in modern applications. (TiAl)1-xMxN thin films in the B1 structure, with 0.06 < x < 0.75, are obtained by alloying with M = V, Nb, Ta, Mo and W, and results show significant ductility enhancements, hence increased toughness, in these compounds. Importantly, these thin films are also predicted to be hard/superhard, with similar and/or increased hardness values, compared to TiAlN. The general, electronic mechanism responsible for the ductility increase is rooted in the enhanced occupancy of d-t2g metallic states, induced by the valence electrons of substitutional elements (V, Nb, Ta, Mo, W). This effect is more pronounced with increasing valence electron concentration (VEC), and, upon shearing, leads to the formation of a layered electronic structure, consisting of alternating layers of high and low charge density in the metallic sublattice. This unique electronic structure allows a selective response to tetragonal and trigonal deformation: if compressive/tensile stresses are applied, the structure responds in a “hard” manner by resisting deformation, while upon the application of shear stresses, the layered electronic arrangement is formed, bonding is changed accordingly, and the structure responds in a “ductile/tough” manner as dislocation glide along the {110}<1 0> slip system becomes energetically favored. The findings presented herein open new avenues for the synthesis of hard, yet tough, ceramic coatings, by tuning the VEC of alloying elements to optimize the hardness/toughness ratio in relevant applications.

Resume : Hydrophilic/hydrophobic polymer composite membranes have known a growth of interest in various separation processes, such as desalination of water, pervaporation, reverse osmosis, gas separation, micro- and nano filtration. They are promising due to their high transport fluxes, which are determined by the formation of a thin layer on the porous support. In this work we describe the synthesis and characterization of porous hydrophilic/hydrophobic composite membranes. Polytetrafluoroethylene-like (PTFE) thin film has been applied by RF magnetron sputtering technique on one side of a polyethylene terephthalate track etched membrane (PET TM) used as a porous substrate. The magnetron sputtering source was mounted in a vacuum chamber with the axis positioned at 45° relative to the axis of substrate holder, which was rotated in order to achieve good uniformity of the PTFE-like deposition. Atomic Force Microscopy (AFM) technique was used in order to assess the deposition rate, while the morphological aspects of the hydrophobic/hydrophilic composite membrane surfaces were studied by Scanning Electron Microscopy (SEM) technique. Chemical composition of the as-resulted PTFE layers was revealed through Fourier Transform Infrared Spectroscopy (FTIR) investigation. The relative wettability of the composite membrane surface was evaluated by measuring static contact angle. Such porous hydrophilic/hydrophobic composite membranes are suitable devices for directional ion transport.

Resume : Cr-based hard coatings are known for many years as suitable protective coating to be used in certain applications such as cutting tools for machining Al and Ti alloys, due to their high fracture toughness and ductility, superior friction behavior as well as good resistance to oxidation, wear and corrosion. The work presents a comparative analysis of the characteristics of the CrN, CrCN and CrSiCN coatings obtained by two deposition techniques: magnetron sputtering (MS) and cathode arc evaporation (CAE). The coatings were deposited on Si and C45 steel substrates in CH4+N2 reactive atmosphere. Film characterization was comparatively performed in terms of elemental and phase composition, texture, surface morphology, mechanical properties (hardness, adhesion) and friction behavior. Research carried out rendered evident that the complex systems (CrCN, CrSiCN) were superior to CrN binary coating in terms of hardness and friction performance, revealing the beneficial effects of C and Si presence in the film composition. Comparing the corresponding coatings produced by the two methods, it was shown that the CAE deposited films possessed higher hardness and superior friction behaviour compared to MS coatings, while smoother surface topography and higher adhesion strength were found for the MS coatings. The highest hardness and the lowest friction coefficient values (~29 GPa and ~0.3, respectively) were obtained for the CrSiCN coating prepared by arc evaporation.

Resume : Amine plasma coatings are actively employed for immobilization of biomolecules, cell adhesion enhancement, gas sensors or grafting of complex moieties. The in-depth distribution of amine groups can play a significant role for the interaction of biomolecules and surface reactions of amine coatings. To date the majority of the amine coatings and films were characterized by X-ray Photoelectron spectroscopy (XPS), spectrophotometric derivatization or IR spectroscopy. In order to obtain a reliable information regarding the in-depth distribution of primary amines (most reactive group among all amine moieties), they have to be derivated with trifluoromethyl benzaldehyde (TFBA) and then analyzed by XPS depth profiling. In this work, the cyclopropylamine plasma coatings were deposited by low pressure radio frequency discharge and their in-depth distribution of primary amines was analyzed by XPS depth profiling after derivatization with TFBA. At the surface of the plasma coatings the NH2/N and NH2/C were 9.4 and 2.5, respectively. Both ratios were rapidly decreasing in depth and they turned to zero after 100s of sputtering. Interestingly, the nitrogen concentration was increase at a shallow depth from 17 to 20 at.% and then remain stable till the interface with the Si substrate has been reached. The explanations why the primary amines are concentrated at the top surface of plasma coatings will be given during the presentation.

Resume : Nitride or carbide silicon thin films, deposited currently by Plasma Enhanced Chemical Vapor Deposition with low (LF) and radio frequency (RF), are used in photovoltaic industry for their passivation and antireflective properties. However, these processes are silane-based and have a low deposition rate which raises costs. To tackle this issue, this work focuses on an alternative organosilicon precursors, namely tetramethylsilane1 (TMS) with two different plasma applicators and gaseous mixtures. Using microwave electron cyclotron resonance plasma applicators or coaxial microwave antennas as plasma sources enables us to obtain relatively high deposition rates. Different gaseous mixtures containing Ar/NH3 and Ar/N2 are studied by means of optical emission spectroscopy (OES) to retrieve information about precursor decomposition and film-forming species. Information about the growing thin film is acquired via in situ interferential reflectometry which gives us real-time insight about the optical path of the light inside the thin film. We looked into various species with OES (NH, N2, CH, C2, CN, H2, Hα and SiH as well as their ratios) and correlated their behavior to the growing thin film. FT-IR spectra of thin films deposited under plasma conditions resulting in silicon nitride, silicon carbide and silicon carbonitride films were also investigated. Refractive index in the IR range could be determined from the FT-IR spectra, and the refractive index in the visible range has been extracted from UV-visible transmission measurements. Thin films underwent further characterization via AFM, XPS and SIMS. This work is supported by French National Research Agency (HD-Plasm-A-SiNOC:H project: laboratoire PROcédés, Matériaux et Energie Solaire/ Institut des Matériaux de Nantes/ Institut de Chimie de Clermont-Ferrand/ Institut Jean Lamour-France).

Resume : Nano-layers of low and also high Z such as Mo, W, Ta, C, Si and B were deposited on glass substrates by Thermionic Vacuum Arc (TVA) plasma. Their adherence, thickness, waviness and roughness as well as the presence of defects were investigated using standard surface analytical techniques. In order to assess the applicability of the TVA technology for X-ray mirror fabrication, we have also synthesized bi-layer combinations of these elements and investigated adherence and inter-layer stress. The X–ray reflection power of the best quality samples was also assessed. A comparative study of the bi-layer combinations was undertaken aiming at finding the optimal deposition parameters and material combinations for the mentioned purpose. Conclusions are drawn regarding the advantages and disadvantages of the technology.

Resume : Proposed work is dedicated to research of conditions for deposition of multilayer (Ti,Al)N/(Si,Al)N coatings for protective proposals. First serials of single layer (Ti,Al)N, (Si,Al)N and multilayer (Ti,Al)N/(Si,Al)N were deposited by reactive magnetron sputtering on glass, silicon and steel substrates. Total thickness of coatings varies in range of 0,1÷1,5 µm. Expected values of bilayer thickness in multilayer films is from 8 up to 40 nm. Basic structural, elemental and phase analysis were performed and will be compared in couple with deposition conditions and mechanical properties.

Resume : This paper is focused on study of multilayer CrN/MoN coatings, their structure, elemental and phase composition. Coatings were obtained by using Arc-PVD deposition on high speed steel substrate in vacuum-arc unit “Bulat-6”. The total thickness of each coating is 8÷13µm. 6 samples have various numbers of layers in coating: 11, 24, 44, 88, 180, 354 and hence they have different bilayers thickness. Elemental analysis was performed using energy-dispersive X-ray spectroscopy (EDS) and wavelength-dispersive X-Ray spectroscopy (WDS). Surface morphology and cross-section were analysed with scanning electron microscopy (SEM). X-ray diffraction measurement (XRD) and Electron backscatter diffraction were used for structure characterization. Mechanical properties will be studied and the relation between them and deposition conditions, layers thickness and structure will be found.

Resume : Fabrication of protective coatings with various functional purposes is one of the main task of industry, material science and solid state physics. This work is focused on study and characterization of coatings, based on metal nitrides MoN which could be used in coatings for protective proposals. Samples were obtained on high-speed steel X18H9T substrate using Arc-PVD deposition in vacuum-arc unit “Bulat-6”. The thickness of coating was ranged from 7 µm up to 22 µm. Elemental composition analysis of coatings was performed using Energy-Dispersive X-ray Spectroscopy (EDS) and Wavelength-Dispersive X-Ray Spectroscopy (WDS), both methods are compared. Morphology of coatings and surface topography were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. Structure-phase composition of coatings was investigated by X-ray Diffraction Analysis (XRD) and Electron Backscatter Diffraction (EBSD). The hardness and elasticity values of coatings are also shown. Coatings were evaluated by Scratch Testing. Relations between deposition conditions and features of the structure, composition and physical-mechanical properties of obtained coatings were found. The interaction at the interface between the steel substrate and MoN coatings under stress was found.

Resume : We demonstrate fabrication of novel ultrasensitive microfluidic biosensor using NV centre detection in thin film diamond diamond. The innovative detection concept is based on combination of electrochemical device combined with nitrogen-­‐ vacancy (NV) centre optical readout. The device consists of 20 μm thick highly ([p]≈10 21 cm­‐3) boron doped homoepitaxial (100) diamond, with a smooth surface of Rms < 1 nm, covered by ~ 15 nm thin intrinsic epitaxial diamond, containing single NV centre sites incorporated in the i‐layer. The surface of the i­‐layer was oxygen terminated. The functionality of the sensor was studied by controllable adsorption of polyethylenimine (positively charged cationic polymer) onto the device surface. The occupation of the NV0 /NV­‐ charged states was controlled by the electric field. We demonstrate a reversible switching of the NV centre charge state from non-photoluminescent to photoluminescent state by applying of the planar bias voltage on the aluminium electrodes. The applied electric field allows for setting up the operation point of the device, by controlling the quasi Fermi levels, while the charged attached molecule lead to a deviation of the band bending over the junction and consequently in the luminescence change. Mathematical modelling was used to simulate the band bending under different applied voltage, applied to the device. The final aim of this work is to combine electrochemical sensing with single site NV optical readout.

Resume : Transitional metals carbides and nitrides have been extensively investigated as protective coatings since they possess both excellent ceramic and metallic properties, which are very useful for applications where there is a combination of high temperatures, corrosive gases, or high level of radiation. The pulsed laser deposition (PLD) technique is useful to grow thin carbide and nitride films to investigate their properties. We deposited ZrCN and TiCN thin films using the PLD technique under various conditions on Si substrates and investigated their properties. X-ray reflectivity technique was used to measure the films density, while the structure, texture and microstress levels were obtained from analysis of diffraction patterns obtained in both grazing incidence and symmetrical X-ray diffraction. Mechanical properties have been assessed by nanoindentation (resulting in hardness and elastic modulus values) and by scratch and wear testing to obtain the critical loads concerning the adhesion to the substrate, wear rates and friction coefficients. The chemical composition, density and thickness were extracted by modelling Rutherford backscattering spectra acquired with 2.2 MeV alpha particles. These investigations helped us understanding the interdependence between structure, composition and properties of Zr and Ti carbo-nitride thin films.

Resume : In recent years, interactions of atoms and molecules with carbonaceous nanosystems have been of great importance on account of their physical and chemical properties allow elucidate diverse technological applications. However, experimental and theoretical analysis of these interactions has difficulties to establish values of adsorption energy, essential for determine when physisorption or chemisorption processes occur. The main goal of this theoretical work is determine the role of the exchange-correlation functional in the adsorption energy of atoms or molecules by Two-dimensional honeycomb lattices. Using Density Functional Theory into Generalized Gradient or Local Density Approximation with different exchange-correlation functionals, we study the interactions between atoms of Al or Water molecules with honeycomb monolayers, for example graphene, silicene or germanene. Atoms or molecules may fall down over an atom or bond in the monolayer. Also, it may fall down in the center of the hexagonal pattern. Total energy curves as a function of distance between atom/molecule and monolayer are evaluated for different exchange-correlation functionals. In particular the Ceperly-Arder and the Perdew-Burke-Ernzerhof exchange-correlation functionals are used. Also, we take into account that the interaction between a water molecule and a hexagonal monolayer can be a dipole - induced dipole interaction. For this reason, we calculated total energy curves with a DFT implementation that use van der Waals interactions, for example the SIESTA code.

Resume : One of the grand challenges in material science is to develop the efficient and low-cost sensors for quick detection of various toxic and carcinogenic molecules, which require rather lengthy procedures or costly techniques for detection. These challenges can be tasked with carbon nanowall-based sensors, where the thin film maze-like structures are deposited on silicon substrates with plasma-enhanced chemical vapour depositions. These sensors demonstrate the high sensitivity in response, selectivity and reversibility for the vapour detection of volatile organic compounds, when tested by an electrical resistance method during adsorption and desorption cycles. The maze-like structures of carbon are composed of several layers of vertically aligned sheets - mostly graphene. The structures are deposited from two different plasma gas mixtures generated either in CH4 or C2F6 with H2. Herein the neutral H atoms are generated in surface wave plasma region driven by a 2.45 GHz microwave power supply and then mixed with CH4 / C2F6 and deposited in capacitively coupled plasma region operating at 100 MHz. By variating plasma processing parameters, we are able to achieve even different wall-to-wall distances ranging from 50 nm and 300 nm when prepared on silicon wafer substrate. Sequently these structures are subjected to different organic vapours of: DMA; urea; iso-pentane; diethyl ether; acetone; methanol; different hydrocarbons; etc. in order to evaluate the relationship between the change in resistance, molecular weight of the adsorbent, the polarity and the bonding/interaction type. For assessment and unravelling the detection mechanisms different surface analyses methods (XPS, Raman, FTIR, SIMS, UV-Vis) are applied prior, between and at the end of molecule detection. The properties of carbon nanowalls are then linked, and will be discussed in respect to the properties of detected molecules.

Resume : Thanks to the long-term stability of their properties, hydrogenated amorphous carbon thin films (a:C-H) are very promising materials for numerous applications including coatings of data storage devices. In order to improve their performances, a full understanding of their local chemistry is highly required.1 Fifteen years ago, according to the seminal work of Ferrari et al.2, electron energy loss spectroscopy (EELS) was the most used technique to get such kind of quantitative information on these materials. Nowadays the complexity of the physics phenomena behind the EELS spectroscopy is well known3 and this technique is regarded as time-consuming and difficult to interpret properly. Other optical techniques such as Raman spectroscopy are now clearly favored by the scientific community. However they still lack of the spatial resolution that EELS in a scanning transmission electron microscope offers for getting direct chemical information. In this contribution, we will revisit the procedures to extract properly and reliably quantitative chemical information from EELS spectra. In addition, the coupling of multi-wavelength Raman and EELS spectroscopies to extract a wealth of chemical information will be discussed. Our results provide a complete combination of C-hybridization, spatial elemental analyses and structural defects studies for shedding light on these complex materials. We will show in particular how the deposition process induced a gradient of sp2 fraction in the thin films and how this gradient is cured as a function of the annealing time. 4 1 C. Casiraghi et al., Materials Today 10 (1), 44-53 (2007) 2 A.C. Ferrari et al., Phys. Rev. B 62 (16), 11089 (2000) 3 P. Schattschneider et al., Phys. Rev. B 72, 045142 (2005) 4 L. Lajaunie, C. Pardanaud, C. Martin, P. Puech, C. Hu, M. J. Biggs and R. Arenal, Advanced Spectroscopic Analyses on a:C-H Materials: Revisiting the EELS Characterization and its Coupling with multi-wavelength Raman Spectroscopy, submitted.

Resume : Over the last few years, a broad panel of carbon materials was proposed for sensing applications. Among these materials, nanoporous carbon (np-C) is of particular interest due to its high specific surface area and low fabrication cost. In this contribution we report on the synthesis of np-C thin films using an original approach combining the growth of copper/carbon nanocomposite thin films by co-sputtering followed by a selective wet etching of copper in nitric acid. We show that the metal nanoparticles of such heterogeneous material must be percolated to obtain an open nanoporosity. We further show how the pore size and the structure of the carbon skeleton can be controlled by adjusting the deposition conditions (e.g., powers applied to the targets, deposition temperature) of the nanocomposite thin films [1]. Furthermore, the possibility of integrating such nanoporous materials in field effect transistors for sensing application will also be discussed. [1] Bouts et al., Carbon 2015, 83, 250.

Resume : Dewetting of a thin polymer film on physically heterogeneous substrates is known to result in numerous ordered meso scale structures. This work reports the dewetting of a thin bilayer of Polystyrene (PS) and Poly(methylmethacrylate) (PMMA) on a topographically patterned non wettable substrate comprising array of pillars, arranged in a square lattice. With increase in the concentration of PMMA solution (Cn–PMMA), the morphology of the bottom layer changes as: 1) aligned array of spin dewetted droplets arranged along substrate grooves at very low Cn–PMMA; 2) threads surrounding each pillar at intermediate Cn–PMMA; and 3) continuous bottom layer at higher Cn–PMMA. The morphology of the PS top layer depends largely on the nature of the pre-existing bottom layer, in addition to Cn–PS. When both Cn–PMMA and Cn–PS are very low, an ordered array of core–shell droplets forms right after spin coating. The bilayers with other initial configurations evolve during thermal annealing, resulting in variety of ordered structures. We observe some unique morphologies such as laterally coexisting structures of the two polymers confined within the substrate grooves due to initial rupture of the bottom layer on the substrate followed by a squeezing flow of the top layer, an array of core-shell and single polymer droplets arranged in an alternating order etc. Apart from ordering, under certain specific conditions significant miniaturization and downsizing of dewetted feature periodicity and dimension as compared to dewetting of a single layer on a flat substrate is observed.

Resume : Polydopamine (PDA), a carbon- and nitrogen-containing polymer, has recently attracted a great deal of attention as a conformal coating material for the functionalization of metal oxide scaffolds for energy application. It is known as a polymer for facile and homogeneous surface coating that virtually sticks to the surface of all types of solid materials, regardless of their chemical nature. With this contribution we describe how the chemical treatment of TiO2 nanotubes (TiO2 NTs) can affect the self-polymerization and deposition reactions of PDA. In particular, we show that simple immersion of the TiO2 NT substrates in a slightly alkaline dopamine solution results in the spontaneous deposition of thin adherent PDA films. However, if the TiO2 NTs are first exposed to a H2SO4/H2O2 solution, dopamine polymerization occurs in the solution and the adhesion process is totally quenched. We propose that H2O2 dehydrates the TiO2 surface and ascribe the observed inhibited deposition to the absence of OH-terminated surface sites no longer available for strong binding PDA. Consistent results are obtained also if TiO2 compact oxide layers are used, leading to the conclusion that the observed results is independent of the surface morphology of adopted layer.

Resume : Boron nitride nanofibers (BNNFs) have diverse area of applications including high temperature composites and electrical nano-insulators due to their excellent thermal and electrical properties. In this study, fabrication and characterization of BNNFs are studied. The synthesis of BNNFs has two successive steps as the electrospinning and the nitridation. Electrospinning is a method which can easily be scalable, cheap and simple. First, electrospinning solution is prepared by using polyvinylbutyral (PVB), boron oxide (B2O3) and ethanol. The prepared solution is electrospun to achieve composite B2O3/PVB nanofibers (BOFs). Nitriding with NH3, O2, N2 is applied to BOFs in a high temperature tube furnace and finally BNNFs are obtained. Scanning electron microscopy (SEM) used for morphological analysis demonstrated that fiber formation was uniformly achieved. Fourier Transformation Infrared (FTIR) spectroscopy is also conducted to identify phase formation of BNNFs. Results of FTIR confirmed that BN is gained from B2O3. For further investigation the effects of concentrations on the structural and morphological properties of BNNFs at different weight ratios of B2O3 and PVB is studied. In addition, time and temperature effect on the BNNF formation is studied to reduce the time of nitridation step. BNNFs/polymer composite materials are also investigated by monitoring the effect of BNNFs on thermal conductivity and mechanical properties for high temperature applications.

Resume : It is well known that dimensionality is one of the most important parameters for materials, and two dimensional (2D) layered materials are of particular concern from both scientific and application points of views due to their distinctive planar structures and properties. Due to their exceptional structural, physical, and chemical properties, 2D materials are anticipated to have important impact on various applications, ranging from electronics to opto-electronics, sensors, energy storage and field emitters. Recently, 2D hexagonal boron nitride (hBN), which can take the form of nanowalls, nanosheets, etc, has generated a lot of interest. Despite many great efforts, synthesized hBN structures retain a considerable amount of defects and unwanted BN phases, i.e. amorphous (aBN) and turbostratic (tBN) boron nitride, particularly at the initial stage of thin film growth. The presence of those phases is largely dependent on chemical dynamics at the interface of ionized/neutral particles and substrate surface. Diamond’s many excellent properties, such as a negative electron affinity (NEA) on hydrogen terminated surfaces, mechanical hardness, and high thermal conductivity, make nanocrystalline diamond (NCD) thin films an interesting potential substrate material for hBN. For example, field emission devices those take advantage of the NEA of NCD thin films and electric field enhancement of hBN nanowall (hBNNW) structures, maybe an exciting potential application for these materials. This work grows hBNNWs on nitrogen doped NCD (nNCD) films/nanostructures and investigates the role of the diamond film on the crystallinity of the deposited hBNNWs at the interface of the hBN-diamond based heterostructures. The nNCD films are first grown by microwave plasma enhanced CVD, and then the hBNNWs are synthesized on the nNCD films using a home built radio-frequency sputtering system. Superior field electron emission (FEE) properties of the given structures are observed. The FEE properties of hBNNWs-nNCD heterostructures show a low turn-on field of 15.2 V/m, a high FEE current density of 1.48 mA/cm2 (at an applied field of 21.3 V/m) and life-time stability up to a period of 248 min. These values are far superior to those for hBNNWs grown on Si substrates without the nNCD films, which have a turn-on field of 46.6 V/m with 0.21 mA/cm2 FEE current density (at an applied field of 91.6 V/m) and a 27 min life-time stability. A cross-sectional transmission electron microscopy (TEM) investigation reveals that the utilization of the diamond interlayer circumvents the formation of amorphous BN prior to hBN growth. Incorporation of carbon in hBNNWs improves the conductivity of hBNNWs. TEM and Raman spectroscopy show that the hBN crystallization in the hBNNWs deposited on nNCD substrate is higher than that of hBNNWs deposited on Si. Such a unique combination of materials results in efficient electron transport from nNCD to hBNNWs and inside the hBNNWs, resulting in enhanced field emission of electrons from the hBNNWs. Additionally, vertically aligned diamond nanorods (DNRs) are fabricated from nNCD films using nanodiamond particles as mask and hBNNWs are then grown on the DNRs to further enhance the FEE properties of these heterostructures. The potential application of these heterostructures is demonstrated by the plasma illumination measurements where the lowering of the threshold voltage by 350 V confirms the role of hBN-DNR heterostructures in the enhancement of electron emission. Consequently, these hBNNWs-diamond based hybrid heterostructures with superior FEE behaviors is a direct and simple process which opens new prospects in flat panel displays and high brightness electron sources. K. J. Sankaran, S. Turner, and P. Pobedinskas are FWO Postdoctoral Fellows of the Research Foundation – Flanders (FWO).

Resume : Graphene thin films on Diamond-like carbon (DLC) films have been obtained on Si or transparent substrates like quartz by pulse laser deposition (PLD) of carbon at ambient temperature with subsequent thermal annealing performed in Ultra High Vacuum condition up to 1273 K. The surface formation of a graphene-like film on top of the DLC, soon described in Appl. Phys. A, Materials Science & Processing, 71, 433–439 (2000), has been investigated as a function of many parameters (fluence, DLC thickness, annealing temperature). The roughness of the films was set at the atomic-scale level with a high uniformity over a 10*10 mm2 area, as seen by atomic-force microscopy. The formation of graphene films on top of DLC have been characterized by different techniques including X-ray photoemission, Auger electron and electron-energy-loss spectroscopies, Raman scattering. At high thermal treatment (1273K) and medium fluence, these films exhibit high performances as transparent conductors, as determined by conductivity measurements (4 points probe), UV-visible transmittance and work function measurements. This infers high figures of merit (conductivity of transparency). As an application an organic photovoltaic cell has been achieved with such films (without graphene film transfer) in the direct configuration and it exhibits a diode behavior.

Resume : Ultrathin carbon films were grown on 4 different types of metallic substrates. Free-standing foils of Cu and Ni-Cu alloy were prepared by electroforming and a pure Ni film was obtained by galvanic displacement on a Si wafer. As a reference substrates, were used the commercial foils of Ni 99.95%. Carbon films were grown on these substrates by CVD in a CH4 - H2 atmosphere at 1000 °C. Obtained films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The XPS at grazing collection angle was used to determine the thickness of carbon films on different metals. XPS analyses were carried out by using an Escalab 250Xi (Thermo Fisher Scientific Ltd, UK) equipped with a monochromatized Al source and electromagnetic lenses for chemical imaging. AES spectra were acquired by using electron gun LEG200 in the analysis chamber of Escalab MkII (VG Scientific Ltd, UK). Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area was investigated from Raman data, optical images and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes [1] was determined from C KVV spectra acquired by using X-rays and electron beam. [1] S. Kaciulis, A. Mezzi et al., Surf. Interface Anal. 46 (2014) 966.

Resume : Due to the European directive on chemicals (REACh), hard chromium coatings, produced from highly toxic and carcinogenic baths, must be replaced by “green” solutions by 2016, the date when their use will only be possible under severe restrictions and regulations. So far, alternatives already exist and are commercially available. Nevertheless, the turn to non-critical, fully “green” coating processes and surfaces is far away from being completed. Anticipating the consequences in the near future, substitutes with at least equal or even better properties than CrVI based coatings have to be developed. WC-C thin films have been synthesized using reactive sputtering of W target in Ar-C2H2, and WC target sputtering in Ar. We discuss the influence of the gas mixture, the kind of target, and the bias voltage on the film chemistry (composition and structure), mechanical (hardness) and tribological properties (friction coefficient and wear rate). Properties similar to CrVI based coatings have been obtained

Resume : Multilayer-based X-ray optics depends on the quality of their interfaces. To achieve high reflectivity the interfaces between the two materials forming a multilayer pair have to be sharp and smooth. When the multilayer is periodic one can optimize deposition conditions such that these requirements are met. However, this gets very difficult in a multilayer where the period varies, either randomly or continuously. For example, a multilayer period across the multilayer Laue lens (where the period varies according to the zone plate law) can vary in principle from a few nanometers to several microns. Transitions from amorphous-to-crystalline phase and microstructural changes are material depend. Carbon containing alloys usually shift formation of polycrystalline phase. In multilayers with non-periodic design it is thus desirable to work with materials that remain stable, e.g. in amorphous phase, over extensive range of layer thicknesses. We are interested in carbon-containing W/Si material combinations because it was demonstrated that they form very smooth and sharp interfaces even in multilayers with only ~1 nm layer thickness. We will report about our thermal stability study of W/SiC and WC/SiC multilayers over a large temperature and multilayer period range. In particular, microstructure, surface and interface roughness and stress were investigated as function of the annealing temperature using x-ray diffraction, atomic force microscope, and scanning electron microscope techniques.

Resume : ZrC, ZrN and SiC have been extensively investigated as protective coatings since these materials possess high hardness, high melting point, good thermochemical stability and thermal conductivity. The pulsed laser deposition (PLD) technique is very useful to grow thin carbide and nitride films to investigate their properties. A simple control of the deposition conditions will results in the deposition of films having various metal to carbon or nitrogen atoms ratios, grain sizes, texture level and stress levels. We deposited mixtures of ZrC/SiC and ZrN/SiC films having a continuous composition range from rich ZrC or ZrN to rich SiC along the main transversal axis using the combinatorial PLD technique. Films were deposited on Si and highly polished Ti substrates to identify conditions that will results in nanocrystalline or even amorphous films exhibiting good mechanical and thermochemical properties. X-ray reflectivity, grazing incidence and symmetrical X-ray diffraction, nanoindentation, scratch and wear testing techniques were used to characterize the structure and mechanical properties of the films. Electrochemical measurements involving corrosion and electrochemical impedance spectroscopy studies were carried out in physiological solutions at room temperature to evaluate the chemical stability of the titanium, bare or covered with the PLD grown films and to compare their performance.

Resume : This work deals with the synthesis of highly active and high surface area Pt-free catalyst and its integration in proton exchange membrane fuel cells (PEMFCs) devices. Among the potential candidates, tungsten oxycarbide (WOxCy) appears to be attractive since it presents some Pt-like catalyst behaviours even though just a few studies have been led. Tungsten oxycarbide can be prepared by many methods, but the key issue in synthesis is the difficulty to produce films at room temperature with high surface area. This work focuses on the synthesis of highly porous WOxCy films by reactive r.f. magnetron sputtering on GDL substrates. For this purpose, a deposition vessel was specifically developed and connected to an X-ray Photoelectron Spectroscopy system in order to achieve in-situ chemical characterization. The effect of processing parameters on the chemical and microstructural properties of the films was investigated. This study has evidenced the major role of the CH4 flow rate, dCH4, the O2 partial pressure, PO2 as well as the plasma power. The chemical composition of the films can be controlled by playing with these parameters: the (O+C)/W atomic ratio in the top most layers of the film can vary from 1.4 to 5.6 while the O/C one can be tuned from 0.2 to 1.1. The WOxCy layers are found to exhibit a typical columnar growth, the films porosity being strongly dependent on deposition parameters. More porous films are obtained with low values of both dCH4 and PO2, as well as lowest possible power.

Resume : Surgical sutures are used to close wounds or incised tissue and can be either resorbable or non-resorbable, depending on the specific purpose. The non-resorbable surgical sutures need to be biocompatible and have high breaking strength and constant thickness over the entire length. Another very important requirement of non-resorbable surgical sutures is their resistance to chemical corrosion induced by body fluids. Non-resorbable surgical sutures are generally made of steel or polymers. Their main shortcomings are induction of inflammatory reactions and loss of strength during contact with living tissue. One of the best biocompatible materials reported is diamond-like carbon (DLC). Although this material has been synthesized by a large range of deposition techniques over the last twenty years, technologies for large production are not mature yet. We investigated the applicability of thermionic vacuum arc (TVA) for the synthesis of good quality DLC films on polymeric materials commonly used in non-resorbable surgical sutures. Dependence of their thickness, morphology and mechanical properties on plasma parameters was investigated by standard analytical techniques. In order to assess the applicability of the DLC-TVA films in surgical sutures, their corrosion properties were investigated in a series of simulated body fluids. Our work draws conclusions on the TVA deposition parameters necessary for obtaining quality DLC films relevant for surgical suture applications.

Resume : Magnetometry is used in various fields, such as for navigation, biomedical applications, quantum computing, mineral exploration or space exploration. There is a need for highly sensitive (<0,1 pT), stable, robust and compact magnetometry sensors, operating in harsh environments. Diamond, as a carbon material, offers a novel platform for ultrasensitive magnetometry. We demonstrate a method for electrical measurement of magnetic field in based on nitrogen-vacancy (NV) centers in diamond using plasma enhanced CVD grown diamond, in which we generate NV crystallographic defect. We excite NV centers by 532nm, focused, green light, which is inducing two‐photon ionization generating photocurrent. Electrodes fabricated on the top of diamond films are used for spin-­sensitive electron transition detection. External magnetic field leads to Zeeman splitting effect that is use for magnetic detection. Photocurrent readout method compared to ODMR, does not require complex readout optical path, therefore enables miniaturization of the final magnetometry device. With future development and testing we expect further increase in sensitivity, speed and resolution of our measurement system for space applications.

Resume : Owing to their excellent physical, optical, and mechanical properties, amorphous carbon (a-C) films have been the subject of extensive research in diverse fields of science with applications ranging from protective coatings on mechanical/biomedical parts to functional films for energy harvesting devices. a-C, however, suffers from brittleness that limits the extent of its exploitation in applications where scratch resistance and mechanical toughness are required. In this work, we investigate the effect of silver nanoparticles incorporation in an a-C matrix (hydrogenated and hydrogen-free) on the nanomechanical and nanotribological response of the resulting a-C:Ag nanocomposite films. Additionally, the effect of temperature (during and post-growth) on the microstructure and mechanical properties is studied. Two deposition methods were used: (a) Pulsed Laser Deposition and (b) a hybrid RF Ion Beam/Nanoparticle source system. The mechanical/tribological response of a-C:Ag films was studied using nanoindentation whereas the hybridization states and the elemental compositions were quantified through XPS and EDS, respectively. Surface topography/characteristics were probed using AFM and SEM. Experimental results are supported by atomistic simulations. It is concluded that silver incorporation graphitizes, in part, the a-C matrix with subsequent reductions in hardness and elasticity but with a significant improvement on ductility, leading to a material with enhanced nanotribological characteristics. The ability to form nanocomposites with tailored microstructures (sp3, sp2, H, and Me size/content) opens new avenues to coating optimizations for a broad range of applications were mechanical, physical and/or optical properties are required.

Resume : Nanocomposite thin films comprised of metastable metal-carbides in a carbon matrix have a wide application profile. While their deposition using non-equilibrium techniques is established, an understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and their application remains critically limited. Here, we investigate sputter deposited nanoscaled nanocomposites of metastable Ni carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal post-deposition processing via complementary in-situ X-ray diffractometry, in-situ Raman spectroscopy and in-situ X-ray photoelectron spectroscopy. At low annealing temperature (300 °C) isothermal Ni3C decomposition into highly carbon saturated face-centered-cubic Ni and amorphous carbon is observed but without changes to the initial finely nanoscaled nanocomposite morphology. Only for higher temperatures (400-800 °C) isothermal Ni-catalyzed graphitization of the amorphous carbon matrix sets in, which is linked to bulk-diffusion-driven phase separation of the nanocomposite into coarser Ni and graphite grains. This demonstrates that filler phase transformations and nanocomposite morphology modifications can be decoupled which is advantageous from a manufacturing perspective. We identify the high carbon saturation of the Ni filler crystallites at any stage of processing as the key hallmark feature which leads to the observed thermal evolution of the metal-carbon nanocomposites. In a wider context, we discuss our findings also with regard to the recently debated role of metastable Ni3C as a possible catalyst phase in graphene and carbon nanotube growth.

Resume : Nano-structured Cu:CuCNx composite coatings were synthesized by Plasma Enhanced Chemical Vapor Deposition (PECVD) combined with high power impulse magnetron sputtering (HiPIMS). Cu:CuCNx interlayers were generated by using the mixture of Ar, N2 and C2H2 gases in addition to copper target. Cross-sectioned samples reveal a multi-layered nanostructure enriched in Cu, C, N and O in different ratios caused by the periodic deposition. In addition, a systematic study on the effect of cathode voltage on the carbon-copper composite coating’s structural and mechanical properties is presented. Elastic modulus and hardness were significantly improved by using higher cathode voltage. Moreover, the Cu:C ratio can be correlated with the cathode voltage. On the other hand, Cu crystal size and amorphous carbon content remain the same. The correlation of the structural and mechanical properties of the composite with the deposition process parameters has been fundamental in order to generate high dynamic stiffness materials addressing critical engineering vibration-related problems. Further study will investigate the effect of current density on the composite properties. This work is part of HIPPOCAMP project (http://www.hippocamp.eu/) where academic researchers and industrial partners join their skills in the development of nanostructured composites with advanced functional properties for structural components in the automotive and manufacturing applications.

Resume : One way to alter the grain size of the material in the controlled way is by using the co-deposition of two or three materials. This paper will highlight some of the most important developments in the present state of the art in scientific research and industrial practices that involve titanium (Ti) and carbon(C)-based films in different combination prepared by Thermionic Vacuum Arc (TVA) method. Hence, we will focus our attention mainly on the most important developments of the behavior of the shafts, gears, impellers as part of gearboxes, turbines and mobile irrigation machines coated with different nanocomposite in different environment. The recent research on their significant properties and wear mechanisms will be summarized. The morphologies and compositions of the coated surfaces by TVA were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) in order to identify the wear mechanism. Corrosion, debris adhesion, and oxidation were found to be the dominant wear processes. The tribological behavior of the coatings under corrosive conditions (0.9% NaCl solution) was investigated using a ball-on-disc tribometer (6-mm-diameter sapphire ball, 0.15 ms−1 sliding speed, 400 m sliding distance). The unique properties (increasing two times the wear resistance and hardness) are tailored by varying the ratio of the material constituents. (C, Ag, Mg, Ni and Ti), proving valuable characteristics for longer life of the irrigation pumps. Acknowledgement: CNDI–UEFISCDI, project number 160/2012, PN-II-PT-PCCA-2011-3.2-1453

Resume : Nanocomposite materials based on metallic particles embedded in various carbon based matrices have been extensively studied during the last decades due to their interesting optical, electrical and biomedical properties. Among the widely used methods for synthesis of such composite materials are those based on plasma techniques. The present work deals with the use of various configurations based on hybrid PVD/PECVD systems for producing a large variety of composite materials with metallic inclusions. The PECVD process insures the synthesis of the matrix, which can be, according to the precursors used an experimental conditions, from polymeric materials to nanostructured carbon, while the PVD plasma source is a magnetron sputtering gun functioning with a metallic target which provides the metallic incorporation in the composite. A great diversity of nanocomposites can be synthesized in such hybrid PVD/PECVD systems, and they can find extensive range of applications. Examples will include combinations of amorphous hydrogenated (or deuterated) carbon materials (a-C:H and a-C:D) with W inclusions as model layers with relevance in fusion research, polymeric materials (polythiophene and polypyrrole) with Cu and Ag nanoparticles for surface plasmon resonance effect, polysiloxane and silicon dioxide-like matrices with various Cu or Ti content for antimicrobial or biocompatible materials, as well as carbon nanowalls decorated with metal (Au, Ni, Pt) for catalytic applications.

Resume : Recently, terrestrial carbonaceous debris produced by atmospheric hypervelocity-shock aeroplasma processes have been identified as resistant metal-polymer nanocomposites (RMPN) [1]. The synthesized filaments exhibit a nanostructured assemblage of either a polymer matrix made out of alkanes with pure or oxidized metal nanoinclusions with phosphate and sulfur particles, or a metallic matrix with polymer agglutinates. To better investigate the properties of such materials, plasma synthesis of carbon-based nano-composite wires doped by metallic nanoparticles was performed using discharges in heptane. Discharges in liquid are ideal to grow wires with very similar features to RMPNs’ [2]. The synthesis process is two-fold. First, nanoparticles of carbon, produced by decomposition of heptane in discharges, are created to form a nanofluid. A pulsed plasma is ignited between two metallic pin electrodes by applying voltages up to 15 kV. Next, the gap distance is increased from about 100 µm to more than 2 mm. With such a large gap, no breakdown is possible. By repeating these steps, the liquid get enriched in wires. The wires are often assembly of 2 or 3 wires with smaller diameters. They can be several millimeters long and are generally insulating. Indeed, the matrix is a hydrogenated amorphous carbon. Although metallic nanoparticles are embedded in the matrix, the percolation threshold is likely not reached, preventing the wire from being conductive. A special attention will be paid in this work to the growth mechanism of the wires. By using ultrafast video imaging (up to 500,000 frames/s), we could get insight into the way wires are produced. [1] Courty and Martinez, Procedia Engin. 103 (2015) 81 [2] Hamdan et al., Mater. Lett. 135 (2014) 115

Resume : Our work deals with thin films of silver phthalocyanine (disc shaped molecules containing carbon and nitrogen atoms) carrying gold, palladium and silver nanoparticles. We varied type (Au, Pd and Ag) and amount (equivalent to 1 – 50 nm thick layers) of metal sputtered on or under phthalocyanine layer, for underlying nanoparticles also alumina substrate temperature (20 – 600 °C) and investigated properties of created nanostructures. Layer/nanoparticle growth was continuously monitored through in-situ conductivity measurements. Processes which occur within thermal annealing (at 160 °C for 2 hours in the air) were studied with SEM surface morphology scans. If the amount of metal is low enough (i.e. less than equivalent layer with thickness of 4 nm for Pd, 5 nm for Au and 8 nm for Ag) metal clusters on organic surface are created. Continuous incompact layers are formed for slightly greater amounts of sputtered metal. Continuous compact layers for significantly greater amounts ( ≈ 15 nm). Annealing generally shifts the percolation threshold to greater amounts of metal. Optimized metallic cluster arrays were finally applied for detection of nitrogen dioxide and two most widely used taggants in explosives. The taggants’ vapors were detected in two modes: without or with photoactivation (λ = 266 nm). While the dc-response of Pd/AgPc sensor to 189 ppm of non-activated 2-nitrotoluene vapors was negligible (i.e. around 1), with photoactivation the dc-response rose to 373.

Resume : Ag nanoparticles have been well known for their properties of localized surface plasmon resonance (LSPR). LSPR can be used in many areas including increased efficiency solar cells, OLEDs, lasers, chemical and biochemical sensors or different medical applications. Although the use range of Ag nanoparticles is quite wide, they are prone to mechanical or chemical damage. One way to solve this problem is the incorporation of Ag nanoparticles in diamond-like carbon (DLC) matrix as DLC is known for its excellent chemical and mechanical stability. In the current research LSPR dynamics of Ag nanoparticles with different atomic concentration embedded in a DLC matrix were analyzed. DLC films (100 nm in thickness) with different metal content were synthesized on fused quartz substrates employing unbalanced magnetron sputtering of Ag target with argon ions in acetylene gas atmosphere. The size of nanoparticles and chemical composition of the films were determined employing SEM-EDS, TEM. Optical properties were analyzed with UV-VIS-NIR spectrometer, while ultrafast processes - employing transient absorption spectrometer (HARPIA, Light Conversion Ltd.). The size/concentration effects of nanoparticles and influence of excitation wavelength on LSPR relaxation dynamics in DLC:Ag nanocomposite films were studied. We have found that the transient absorption spectra relaxation dynamics depends on the size distribution of nanoparticles and ultrafast energy transfer processes between the nanoparticles and host matrix are negligible. The results suggest that excitation at different wavelengths (0.4 – 1.2 μm) enables to follow dynamics of plasmon relaxation Ag nanoparticles of different size.

Resume : Nanocomposite metal/dielectric films consisting of metal inclusions embedded into a polymer matrix are widely used as attractive materials for research and application. They can have interesting optical, mechanical and electrical properties. Especially, the electrical properties are influenced by structural and morphological properties of the nanocomposite materials. The paper concentrates on the morphological properties of nanocomposites and a very efficient tool for their assessment is presented. The evaluation of morphology can help to learn more about electrical properties; consequently, desired properties can be projected by a proper nanocomposite morphology and therefore suitable technology of preparation. The goal of the morphological analysis of the 3D nanocomposites is to derive main characteristics as local metal particle concentration, their size distribution, or their spatial distribution using 2D images (e.g. TEM images). It is an ill-posed task; hence the results can be only approximate. The paper focuses on the spatial distribution evaluation. Many morphological methods have been used for 2D structures. Nevertheless, results presented here show methods suitable in the case of 3D nanocomposite structures when its objects are more or less randomly distributed in space and have various dimensions. A low metal volume fraction is supposed. The computer tool enables a subsequent analysis of electrical properties of the films and their dependence on the morphology.

Resume : Physical attributes of multicomponent materials of a given chemical composition are determined by atomic arrangement at property-relevant length scales. A potential route to access a vast array of atomic arrangements for material property tuning is by synthesis of multicomponent thin films using vapor fluxes with their deposition pattern modulated in the sub-monolayer regime. However, the applicability of this route for creating new functional materials is impeded by the fact that a fundamental understanding of the combined effect of sub-monolayer flux modulation, kinetics and thermodynamics on atomic arrangement is not available in the literature. Here we present a research strategy and verify its viability for addressing the aforementioned knowledge gap. This strategy encompasses thin film synthesis using a route that generates multi-atomic fluxes with sub-monolayer resolution and precision over a wide range of experimental conditions, deterministic growth simulations and nanoscale microstructural probes. Investigations are focused on structure formation within the archetype immiscible Ag-Cu binary system, revealing that atomic arrangement at different length scales is governed by the arrival pattern of the film forming species, in conjunction with diffusion of near-surface Ag atoms to encapsulate 3D Cu islands growing on 2D Ag layers. The knowledge generated and the methodology presented herein provides the scientific foundation for tailoring atomic arrangement and physical properties in a wide range of miscible and immiscible multinary systems.

Resume : We have previously shown [Zenkin, S., Kos, Š., Musil, J. (2014), Journal of the American Ceramic Society, 97: 2713–2717] that oxides and nitrides of low-electronegativity metals form intrinsically hydrophobic hard ceramics needed for various harsh-environment applications. The van Oss-Good-Chaudhury approach based on the Lifshitz-van der Waals/acid-base theory used for the analysis of the results revealed that the dominant component of the surface free energy of these ceramics is the electrostatic Lifshitz-van der Waals component, strongly suggesting a thickness dependence of the wetting properties. We used the reactive high power impulse magnetron sputtering with a pulsed reactive gas flow control as a novel technique capable of producing dense films with smooth surfaces and well controlled thickness down to units of nm. We prepared films of HfO2 as a typical case of a low-electronegativity-metal based ceramic. We have found a thickness dependence of the water droplet contact angle ranging from 120º for the thickness of 50nm to 100º for the thickness of 2300nm considered as bulk material. The Lifshitz-van der Waals component of the surface free energy remained the dominant component throughout the range of measurement and exhibited a corresponding thickness dependence. The XRD and FTIR showed only minor differences among the films. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the sub-dominant texture and/or non-monotonic size dependence of the crystal grain surface energy.

Resume : Via homogeneous dissolution of conjugated polymers, such as poly(3-hexylthiophene) (P3HT), poly(9,9-dioctylfluorene) (PFO), and poly(9,9-di-n-hexyl-2,7-fluorene)(PFH), in the melt of crystalline hexamethylbenzene (HMB), binary eutectic systems have been achieved. During cooling from molten state, crystalline platelets of HMB solvent were efficiently developed and spread first, which subsequently initiates epitaxial crystallization of dissolved conjugated polymers. The involved epitaxial relationship selectively induces certain types of ordered molecular packing, including the growth of less stable form of PFO crystalline modification that has been pursued for decades in order to harvest efficient electroluminescence. Regarding the successive molecular organization process within studied binary mixtures, the length of side chains, mixing ratio, molecular weight and the degree of supercooling were found capable of manipulating the organization behaviors including the azimuthal orientation of conjugated backbones relative to substrate; edge-on or face-on orientation were selectively achieved. With the incorporation of carbon nanotubes within these binary systems, the designed crystallization routes of eutectic mixtures were found capable of intercalating 2D oriented arrays of carbon nanotubes within crystalline domains of conjugated polyfluorene. Furthermore, the oriented array of carbon nanotubes is able to induce the growth of shish-kebab crystals of P3HT. These eutectic systems thus unveil the opportunities of modifying optoelectrical properties of organic thin films via introducing new routes of crystal engineering and oriented association of carbon nanotubes.

Resume : Semiconductive conjugated polymers, including polyfluorenes, normally are not miscible with insulate polymethylmethacrylate (PMMA) in melt. Nevertheless it was discovered that these two kinds of polymers are able to form liquid phases of disparate densities in solutions. These polymer liquid phases are able to simultaneously distribute into networks or granular domains upon the variation of mixing ratios. Furthermore, functional materials such as carbon nanotubes and fullerene derivatives were found to blend into one of polymer liquid phases. Based on the success of selectively distributing carbon nanotubes in the liquid phase of Poly(9,9-dioctylfluorene), we attempt to largely enhance the amount of suspended carbon allotropes in solutions in order to achieve continuous organization of carbon allotropes via networks of polymer liquid phases. This is a new mechanism for establishing percolation network of functional carbon allotropes within polymeric thin film for augmenting the performance in various aspects. Moreover, in view of favorable pi-pi interactions with conjugated polymers, crystalline small organic molecules with optoelectrical properties, such as pentacene, anthracene and hexamethylbenzene, are introduced into solutions as an approach to manipulate the network of polymer liquid phases and enhance the preferred distribution of carbon allotropes as well. Upon these results, it is expected to establish a fundamental mechanism to manipulate the development of complex liquid phases in solutions, which can be a novel way to reach desired structures of optoelectrical thin film.

Resume : The growth of carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) in H2/C2H2 atmosphere was achieved using nanocomposite nickel carbon (nc-Ni/C) thin films as catalysts. In order to identify the most favorable conditions to obtain dense CNTs arrays, the Ni contents in the catalysts as well as the growth conditions of the CNTs were varied. According to previous studies,[1,2] nc-Ni/C thin films containing 40, 55 and 65 at. % of Ni were selected. On the other hand, the growth temperature of the CNTs was varied between 500 and 700 °C and the power applied to the PECVD source was tuned from 30 to 50 W. SEM and µ-Raman spectroscopy were then employed to probe the morphology and the structure of the CNT’s. According to the chemical composition of the nc-Ni/C thin films, different trends were observed. No CNTs were obtained neither for the higher nickel content (i.e. %Ni = 65 at. %) nor for the lower temperature (i.e. 500 °C). On the other hand, for temperatures higher than 500 °C, while a high power on the PECVD source (i.e. 50 W) was necessary to obtain CNTs in the case of films with a moderate Ni content (i.e. %Ni = 55 at. %), a low power (i.e. 30 W) was sufficient for the film with the lowest Ni content (i.e. %Ni = 40 at. %). This difference in behavior was attributed to the differences in microstructure of nc-Ni/C thin films which is directly related to their chemical composition.[2] [1] A. Achour, A.A. El Mel, N. Bouts, E. Gautron, E. Grigore, B. Angleraud, L. Le Brizoual, P.Y. Tessier and M. A. Djouadi, Diam. Relat. Mater. 34 (2013) 76–83. doi:10.1016/j.diamond.2013.02.006. [2] A.A. El Mel, N. Bouts, E. Grigore, E. Gautron, A. Granier, B. Angleraud and P. Y. Tessier, J. Appl. Phys. 111 (2012) 114309. doi:10.1063/1.4728164.

Resume : Ag/C:H nanocomposite is a material formed by silver nanocrystallites embedded in an hydrogenated carbon matrix. The metal content, the size and the shape of the nanoparticles have a direct impact on the properties (e.g., electrical, optical) of the nanocomposite material. Therefore, for an applicative aimed, an accurate control of the microstructure of the material is of crucial importance. In this work, we study the synthesis of Ag/C:H nanocomposite using a hybrid process combining magnetron sputtering and plasma enhanced chemical vapor deposition in Ar/CH4 gas mixture. This approach combines the sputtering of a silver target and the simultaneous dissociation of CH4 resulting in the formation of the hydrogenated carbon matrix. In particular, we investigate the influence of the microstructure and the chemical composition on the electrical conductivity of the material. The atomic silver content (at. % Ag) in the layers was found to increase (from 7 to 65 %) when decreasing: i) the CH4 fraction in the gas mixture and ii) the distance between the silver target and the substrate. Cross-sectional SEM micrographs reveal that the morphology of the material evolves from a compact carbon matrix encapsulating silver nanoparticles at low silver content to a granular morphology when increasing the metal amount. By means of the four probe method, one can conclude that for at. % Ag > 60%, the Ag nanoparticles are percolated giving rise to an electrical conductivity about 7.102 S/cm.

Resume : The goal of this work was to study the main characteristics of TiSiC coatings alloyed with stainless steel, which was selected because it contains three main elements (Fe, Ni, Cr) expected to improve the characteristics of TiSiC coating. The coatings were deposited on Si, 316 L and C 45 steel substrates by cathodic arc method in C2H2 atmosphere at different mass flow rates (60–130 sccm). The coatings were investigated in terms of elemental and phase composition, chemical bonds, microstructure, morphology, mechanical characteristics and wear performance. Ti, Fe, Cr, Ni, Si and C atomic concentrations of 27–34 at. %, 2–17 at. %, 0.3–5 at. %, 0.1–2 at. %, 2.5–4.3 at. % and 49–64 at. %, respectively, were determined. The coatings were found to consist of crystalline carbide solid solution (FCC structure) and amorphous hydrogenated carbon phases. The increase in C2H2 mass flow rate led to the decrease in crystallinity and the change of preferred orientation from (200) to a random texture. Hardness and critical load values from 30 to 45 GPa and from 30 to 35 N, respectively, were measured. The tribological tests in dry atmosphere showed friction coefficients and wear rates in the range of 0.2–0.6 and 3–8×10-6 mm3N-1m-1, respectively. The improvement of the mechanical and tribological characteristics with increasing carbon content was evidenced. The best tribological behaviour was found for the coating deposited at the highest C2H2 mass flow rate.

Resume : Silver nanoparticles on insulating supports have a plasmonic resonance stronger than other noble metals. Thus their plasmonic response can be exploited in a wide range of fields: Catalysis, Photonics or Biosensors. However chemical degradation, plasmonic damping and red-shift of Ag nanostructures in ambient conditions can prevent their widespread use. Herein, we have deposited Ag nanoparticles on a 15 nm buffer layer of amorphous Al2O3 by pulsed laser deposition. Later on, some regions of the samples were exposed to laser irradiations. Both regions (as deposited and laser irradiated) are forming discontinuous layers with larger Ag nanoparticles in the case of laser exposed regions. The plasmonic, morphological and chemical evolutions of these Ag nanostructures have been analyzed for 15 months by extinction spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Extinction spectroscopy and electron microscopy have shown that laser irradiated regions are optically and morphologically more stable than as deposited ones, where a progressive blue shift in the plasmonic resonance and a gradual agglomeration of native silver nanoparticles are observed after several months of atmospheric exposure. The chemical characterization of these degradated samples by XPS has revealed that silver nanoparticles have been thoroughly oxidized, and their surface adsorbs noticeable amounts of nitrile species. The formation of a dielectric shell surrounding the core of metallic silver, made of silver oxide and silver nitrile, is proposed. Nitrile species would be formed at the surface of the metallic nanoparticles by adsorption of NO and NO2 from the atmosphere, followed by reaction with CO or other carbonaceous reductive agents, a catalytic reaction promoted by the Al2O3 buffer layer.

Resume : High resistance to corrosion in body fluids is crucial for optimal performance of biomedical devices, so in vitro corrosion resistance investigation of novel biomaterials represents a compulsory requirement. (HfNbTaTiSi)C, (HfTaTiZrSi)C and (NbTaTiZrSi)C high entropy alloy carbide coatings were investigated as possible candidates for biomedical applications. The coatings were deposited on 316L stainless steel substrate through reactive co-sputtering from pure element targets in Ar+CH4 gas mixture. In vitro corrosion behaviour of the coatings was studied in simulated body fluid (pH=7) at 37 °C. The coatings were also investigated for elemental and phase composition, crystalline structure and morphology. The coatings, with almost equiatomic concentrations of metals (8.2-10.9 at.%), with Si content of 6.9 -7.0 at.% and with C/(metal+Si) ratio of about 1.1, consisted of single FCC solid solution phases. Smooth surfaces and columnar cross-sectional morphologies were observed. Compared to the bare 316L substrate, all coatings showed significant better corrosion behaviour in terms of open circuit, corrosion and breakdown potentials, corrosion current density, polarisation resistance and weight loss. (NbTaTiZrSi)C coating was found to be the most corrosion resistant in SBF solution at 37 °C, followed closely by (HfTaTiZrSi)C. This last result can be tentatively ascribed to the film morphology, which appeared to be more compact for these coatings compared to (HfNbTaTiSi)C.

Resume : In this paper we report the preparation of films of vertically-oriented carbon nanotubes by the injection CCVD method. By this process iron particles are continuously incorporated into the growing CNT films. We report the preparation, the structural and chemical characterization of the array by TGA, XPS, TEM, SEM, XRD as well as the magnetic properties. Iron nanoparticles are mainly made up of cementite. The magnetic properties were investigated either with the magnetic parallel or perpendicular to the direction of the carbon nanotubes. Main results may be explained by the preferential anisotropy of the nanoparticles along the direction of the carbon nanotubes.

Resume : We investigate magnetic properties of iron based nanoparticles (NPs) intercalated into carbon nanotube (CNT) aligned arrays for magnetic fields oriented both along and perpendicular to the CNT axes. Samples have been synthesized by floating catalyst chemical vapor deposition. They are characterized by HRTEM and XRD. A low continuous iron concentration in the gas mixture allows to insert selectively the iron particles inside the nanotubes. The NPs are mainly made up of iron carbide Fe3C with different orientations. The NPs density is directly related to the iron concentration. The magnetic properties were investigated eithzer with the field parallel or perpendicular to the direction of the carbon nanotubes.

Resume : Few layer graphene (FLG) was synthesized by µ-wave assisted exfoliation of expanded graphite in toluene with an overall yield of c.a. 7%. A significant difference in the absorption of µ-waves by the expanded graphite and toluene allowed a rapid heating of the medium. The number of FLG sheets varies from 1 to 7, while the lateral size of the sheets exceeds few µms. The obtained FLG exhibits very low resistance with average value of 1.6 kΩ which is comparable to high quality graphenes synthesized by CVD methods, and lower than number of exfoliated graphenes.

Resume : Nanocomposite materials based on matrix-embedded noble metal nanoparticles (NP) are known as very promising materials because nanocomposite often exhibits exacerbate or exotic properties compare to conventional materials. Gas phase aggregation process based on magnetron sputtering is a convenient technique to obtain thin films. NP are produced in a broad range of sizes – from a few nanometers to tens of nanometers– depending on the operating conditions, which reveal many interesting properties according to the size. Metallic Ag and Cu-NP embedded in AlN, Al2O3 and Carbon matrix were deposited using the free NP generator coupled to a conventional magnetron sputtering chamber. An innovation of such device is the ability to use separately, simultaneously or sequentially the two processes, leading to a wide range of nanostructured materials. Variations on Ag and Cu NP sizes will be shown versus the aggregation length distance. Optical properties of the obtained nanostructured materials will be investigated by both ellipsometry and optical spectroscopy pointing out differences related to shape, size and nature of nanoparticles. A comparison between a stack of Ag-NPs, Ag-NPs doped-dielectric and a “conventional” silver thin film will emphasize the role of the density and the percolation threshold on electrical resistivity. Size distributions, shape and surface features of Ag and Cu NP will be discussed and compared using TEM, SEM and AFM respectively.

Resume : We have theoretically studied optical properties of p-doped GaNAsBi/GaAs Single Quantum Well in order to reach the 1.55µm telecommunication wavelength. The calculation are carried out by solving selfconsistently the band (16×16) Kane Hamiltonien combined with the Poisson equation for the hole charge density. We have investigated the effect of p doping density in the well on the subband energies, potential Fermi level and the confining hole density distribution for specific couple (well width〖 L〗_w,Bi composition y), with respect of confinement conditions. The increase of doping density blueshifts the fundamental transition. Furthermore, the case of doped barrier has been discussed. Based on these results, potential applications in long wavelength range are proposed.

Resume : The development of new electrodes for energy storage devices is a complex topic in the last twenty years. A remarkable progress was obtained in the case of vertically graphene -like carbon nanowalls (CNW), based materials. We already demonstrated the efficiency of these electrodes in the utilization in vanadium redox flow batteries [1] and after decoration of CNW with ruthenium oxide nanoparticles in getting high performance electrodes for micro supercapacitors [2]. In this study we focus on plasma processing of CNW electrodes aiming to improve their response/efficiency in electrochemical reactions. We used plasma jet treatment with various gases (nitrogen, ammonia, oxygen etc.) in order to attach new functional groups at surface. The properties of the obtained nanostructured electrodes were investigated by SEM and TEM, Raman, FTIR, XPS, contact angle and cyclic voltammetry (CV). Plasma functionalization of CNW led to the modification of the chemical composition of electrodes surfaces (ratio of C/O/N) and to the embedding of chemical groups that favor electrochemical oxidation-reduction reactions. Acknowledgments: This work was financially supported by UEFISCDI, under projects PN-II-PT-PCCA-2013-4-2066 and PN-II-ID-PCE-2012-4-0629. 1. González, Z., Vizireanu, S., Dinescu, G., Blanco, C., Santamaría, R., Nano Energy, 1, 833, 2012 2. Dinh, T.M., Achour, A., Vizireanu, S., Dinescu, G., Nistor, L., Armstrong, K., Guay, D., Pech, D., Nano Energy, 10, 288, 294, 2014

Resume : When thin hard films on soft substrates are disturbed through external stress/strain stimuli they tend to buckle, creating in the process a nanostructured surface with wrinkled patterns of specific height and wavelength. External stimuli can be strain, caused through temperature modulations, or stresses that are either externally applied or generated during the thin film deposition process. We here report on two, seemingly disparate, routes for surface patterning on polydimethylsiloxane (PDMS) with nanoscale control of the wrinkles wavelength: (a) Argon ion bombardment and (b) hydrogenated amorphous carbon deposition on PDMS. In the former case a hard thin film is generated through the ion bombardment on the surface that changes the chemistry of the first 20-30nm of the PDMS material and stiffens it in response. In the latter case a hard thin film (a-C:H) is deposited on the PDMS surface through plasma enhanced chemical vapour deposition (PE-CVD). In both methodologies the internal stresses generated during the thin film growth trigger the buckling instability of the surface that patterns the material with specific length characteristics. It is observed that the geometrical details of the surface can be indirectly controlled through changes in the relative elastic moduli of the film to substrate or film thickness. AFM, SEM, and uv-vis measurements are used to probe the morphological and optical characteristics of the produced surfaces with potential applications to antibacterial coatings, energy harvesting materials, microfluidic devices, etc.

Resume : Transition metal nitrides have been established as a major category of engineering materials, which find applications in a vast range of technological sectors, such as protective coatings for cutting tools and machinery parts, thin films resistors, Al and Cu diffusion barriers, and ohmic contacts on III-nitride semiconductors. Emerging applications such as plasmonics, hot electron devices, and photo-catalysis require the nitrides to be in nanoparticle form. This is a challenging task due to the oxidizing nature of the transition metals (mostly Ti and Zr), making any ex-situ nitridation process impossible, as well as the high melting point of transition metal nitrides that makes the formation of nanoparticles by thermal dewetting demanding. Therefore, new pathways for the deposition of transition metal nanoparticles in high-vacuum conditions and their in-situ nitridation would be highly desired. In this work, we investigate the deposition of Ti and Zr nanoparticles by a cluster beam source (Nanogen, Mantis), which is based on sputter deposition of Ti and Zr, whose vapours are passing through a high pressure inert gas (Ar) condensation zone allowing for nucleation in the gas phase before deposited on a substrate in nanoparticle form. The nanoparticle size is controlled via a quadrapole mass filter and can vary between 2 to 20 nm. The nanoparticles are then in-situ nitrided by nitrogen plasma generated by an RF ion source. The morphology, crystal structure, surface chemistry and optical properties of the produced nanoparticles are investigated using AFM, XRD, XPS and optical reflection/transmission spectroscopy, respectively. The effect of nanoparticle size and nitridation conditions on the overall response are studied and reported.

Resume : Over the last decades, TiSiC coatings, with or without adding elements, have received considerable attention due to their remarkable properties such as high hardness and strength, chemical stability, superior friction and wear performance, good thermal and electrical conductivity, etc. The goal of the present study was to evaluate the bonding structures in TiSiC-Cr coatings with Cr and Si as alloying elements, using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The coatings were prepared in reactive atmosphere of CH4 and C2H2 hydrocarbon gases by the cathodic arc method. Their properties as derived from these analyses were comparatively examined for similar carbon contents in the films grown in either CH4 or C2H2. The XPS 1 Cs spectra gave evidence of different carbon bonds (C–Ti, C–Ti*, C–Cr, C–C sp2, C–C sp3 and C–O), with proportions depending on the reactive gas used. For example, for the films deposited in CH4, both C–Ti and C–Ti* bonds were detected, whereas for the C2H2 – grown films only C–Ti* bonds were observed. The intensity ID/IG ratio, G peak position and the full width at half maximum of the G peak as determined from the Raman spectra provided information on the sp2 phase clustering, sp3 and sp2 contents, structural and topological disorder etc. Both XPS and Raman analyses showed that the bonding structures were significantly dependent on the precursor gas.

Resume : One of the main goals in the development of wear-resistant ceramic protective coatings is to improve ductility, hence reduce brittleness, while maintaining high hardness, which equates to enhanced toughness. In our previous work, we demonstrated theoretically and experimentally that TiMeN and VMN (Me = W and Mo) ternary alloys possess enhanced toughness as compared to their parent binaries, due to increased valence electron concentration. It is yet unknown whether similar effects can be achieved in the corresponding TiC- and VC-based alloys. We use density functional theory to calculate Ti0.5M0.5C and V0.5M0.5C formation energies, elastic constants, surface energies, and stress-strain curves for selected slip systems. Our results show that cubic Ti0.5Me0.5C and V0.5Me0.5C solid solutions are thermodynamically stable with respect to the mixing of cubic Ti(V)C and hexagonal MeC over a wide compositional range. According to the Pugh and Pettifor empirical criteria, which predict the degree of plasticity vs. brittleness based on elastic constants values, none of the studied alloys is expected to be more ductile than TiC or VC parent binaries. Nevertheless, the room-temperature meta-stability of the cubic alloys leads to the formation of hexagonal stacking faults upon shearing which, promoting {111}<110> slip, allows for stress dissipation via transformation toughening beyond the yield point.

Resume : Matrix assisted pulsed laser evaporation (MAPLE) has been employed for the deposition of composite thin films of layered double hydroxides (LDH) – graphene. MAPLE technique is derived from standard pulsed laser deposition (PLD), where one or more guest molecules (in our case LDH and graphene) are dissolved and subsequently frozen into a light absorbing matrix. When laser light irradiates this matrix, the solvent evaporates and the guest materials are collected on a substrate. Ni/Al based LDH (Ni: Al ratio =3) and lab synthesized graphene were homogeneously dispersed in various solvents, frozen and used as targets for MAPLE experiments. The forth harmonic of a Nd:YAG laser (266 nm) irradiated the target, and the composite thin films were grown on Si substrates placed at a distance of 4 cm. The as deposited thin films were subsequently immersed in aqueous solution with monosodium glutamate of 0.5% concentrations (w/w), to be further used as active element in food additive sensors. The investigation techniques used to analyze the films before and after immersion were X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy(SEM) combined with energy dispersive X-ray (EDX) analysis and Fourier Transformed Infra-Red Spectroscopy (FTIR).

Resume : The amine functionalization of carbon nanomaterials gained a considerable interest thanks to the versatility and reactivity of NH2 groups. The application of amine functionalized carbon nanotubes (CNTs) for gas sensing is an emerging technology allowing for the new level of the detection limit and reliability. In general, the amine functionalization of CNTs is made by multi-step chemical processes. In this work, CNTs were functionalized with amine functions by environment-friendly plasma polymerization of cyclopropylamine (CPA). The X-ray photoelectron, IR and Raman spectroscopies were used to characterize the functionalized CNTs. Depending on the CPA flowrate, the atomic density of nitrogen varied from 2 to 10 at.%. IR spectroscopy confirms that peaks of amine groups are present in the CNTs. By Raman spectroscopy it is found that the ratio of D peak area over the G peak area is increasing with the CPA flowrate. Hence, the amount of the introduced sp3 carbon is increasing with the latter parameter. The gas sensors prepared by using amine functionalized CNTs showed high affinity towards formaldehyde vapours.

Resume : Artificial polymer scaffolds for regenerative medicine have to exhibit very good bioactivity and sufficiently fast biodegradation. It requires research and development of suitable polymers, their structure and surface functionalization. In this work, the first two issues have been solved by preparation of polycaprolactone/polyethylene glycol (PCL/PEG) nanofibers by electrospinning. The optimization of PCL/PEG ratio, polymer concentration and electrospinning conditions (e.g. voltage, electrodes distance) leads the changes of substrate morphology, homogeneity and fiber thickness. The third issue is caused by low bioactivity of polymer materials. Therefore, the surface modification is required to adjust the wettability and introduce bioactive functional groups such as amines useful e.g. for protein bonding. Plasma enhanced chemical vapor deposition has been applied for coating of PCL/PEG nanofibers by amine-rich films from cyclopropylamine in low pressure capacitively coupled discharges (13.56 MHz). The properties of the coated nanofibrous meshes were studied by X-ray photoelectron spectroscopy, IR spectroscopy and scanning electron microscopy (SEM). The influence of PCL/PEG composition and amine overcoat of nanofibers on the hydrolytic stability of nanofibrous foils was investigated after immersion in water at 37 °C by weighting, SEM and chromatography.

Resume : The chemoresistive ammonia gas sensors were based on carbon nanotubes on Si/SiO2 substrates. The sensors were obtained by plasma enhanced CVD of catalytic nanoparticles followed by thermal CVD growth of carbon nanotubes. To improve the sensor response, plasma polymerization of maleic anhydride with different durations (2 - 7 min) was used. The sensors obtained were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. The link between the functionalization of active layer and defectiveness of carbon nanotubes was determined. Plasma functionalization allowed to increse the sensor response from 0.5 % to 3.6 % (for 500 ppm of ammonia) using treatment during 5 min.

Resume : ncorporating inorganic nanoparticles into conjugated polymer matrices is an area of current interest in the fields of organic optoelectronics and photovoltaics. The obtained composite can have high optical properties from the organic component and advantegeous electrical properties and stability from the inorganic one. Such materials are widely employed in organic electronic devices such as light-emitting diodes or solar cells We have investigated nanocomposites composed of titanum dioxide (TiO2) nanoparticles and poly(3-hexylthiophene)(P3HT), by focussing on the charge transfer process between P3HT and TiO2. The photoluminescence results revealed that incorporation of TiO2 nanoparticles in concentrations up to 0.3 mM significantly enhanced the luminescence intensity of P3HT when exposing to light of energy higher than TiO2 bandgap. The observed variation suggested an energy transfer from TiO2 nanoparticles to P3HT.Meanwhile, when P3HT/ TiO2 composites were exposed to light of energy below TiO2 bandgap, the nanoparticles gradually quench the fluorescence of P3HT,demonstrating the injection of excited electrons from lowest unoccupied molecular orbit of P3HT to the conduction band of TiO2

Resume : Graphite oxide synthesis dynamics was investigated by the sampling technique. The synthesis of graphite oxide was carried out by the modified Hummers method. Small probes of solid phase (30-50 mg) were collected from the reactive mixture and analyzed by thermogravimetry and differential scanning calorimetry. Additionally, the samples obtained were analyzed by scanning electron calorimetry, X-ray diffraction and energy dissipative X-ray spectroscopy. The strongest oxidation was detected after 10 min of synthesis started after the addition of KMnO4. The intercalation of graphite starts from the step after 30 min of synthesis beginning when temperature was increased to 35°C. The time intervals during which the intensification can be applied were estimated.

Resume : We report on the direct deposition of nanostructured carbon (fibers and flakes) on ceramic foams via downstream deposition in an expanding radiofrequency argon plasma beam discharge injected with acetylene and hydrogen as active gas. The ceramic foams are fabricated from red mud collected as waste product from aluminum industrial production. The nanostructured carbon films are deposited on the red mud derived ceramic foams aiming to increase their affinity for hazardous organic pollutants from waste water and hence to increase their potential catalytic activity for their oxidation. The Fe dispersion and the mechanical properties of the ceramic foams supports influence the morphology of the nanostructured deposited material. The obtained carbon structures have been investigated by SEM coupled with EDX, XRD, and Raman spectroscopy.

Resume : Myoblast are myogenic precursors that proliferate, activate, and differentiate on muscle injury to sustain the regenerative capacity of skeletal muscle. Therefore, myotube formation plays an important role in restoring muscular functions, and substrates to promote the differentiation of myoblasts to myotubes need to be developed for muscle tissue engineering. We developed the nanowires with different densities (low, medium and high) using polyaniline (PANI) and plasma modified polyaniline (P-PANI) and investigated the L6 cell differentiation on them. The plasma modification was performed by pulsed plasma polymerization of cyclopropylamine described previously to yield functional coatings containing up to 9 at.% of amine groups. The L6 myoblast cell proliferation rate and total protein content by using PANI nanowires with all densities were similar but it varied for P-PANI nanowires. It indicates that P-PANI nanowires substrates can modulate the induction of myoblasts into myotube formation without additional electrical stimulation, suggesting that these fibers may have potential as a temporary substrate for skeletal tissue engineering.

Resume : Plasma polymers, i.e. materials that are created as a result of the passage of organic vapour through plasma, are due to their unique properties employed in impressive range of applications. Although films of plasma polymers are traditionally described as smooth and pinhole free, the possibility to produce nanorough and nanostructured plasma polymerized coatings receives increasing attention. Two different approaches based on application of gas aggregation sources of plasma polymerized nanoparticles (NPs) that enable fabrication of such materials will be presented. The first strategy is based on the deposition of film of plasma polymerized NPs that is subsequently overcoated by a thin film of plasma polymer with desired chemical structure. It will be shown that this makes it possible to control independently surface chemical composition of produced surfaces, which is linked to the chemical structure of the overcoat layer, and roughness, which is given by the size and surface density of NPs that form the base layer. Furthermore, the same process my by adapted also for production of nanocolumnar structures of plasma polymers when glancing angle deposition is used instead of conventional PE-CVD or RF magnetron sputtering. As observed, this enables to prepare coatings with adjustable size of produced nanocolumns, which is determined by the size of NPs used as seeds for the growth of nanocolumns, and their spacing, which is dependent on the surface density of NPs.

Resume : Primary amine-based plasma polymer films (PPFs) attract great attention for various biomedical applications (biomolecule immobilization, biosensor development,…). In this context, to better understand the growth mechanism of such coatings, we investigate the impact of the precursor mixture on plasma chemistry and ultimately on PPFs properties evaluated by gas phase FTIR and mass spectrometry and FTIR and XPS, respectively. PPFs are synthesized from both cyclopropylamine (CPA) and ammonia/ethylene (NH3/C2H4) mixture in low pressure (2.7 Pa) inductively-coupled plasma discharges keeping the N/C ratio constant in the precursor flow rate. The studied parameter is the power injected in the discharge. The results show that, in similar deposition conditions, the use of CPA allows a better nitrogen incorporation in the film compared with the NH3/C2H4 mixture. This is attributed to the presence of C-N bonds in the CPA molecule, while for the mixture, NH3 and C2H4 molecules and fragments do not react in the gas phase and are therefore incorporated separately in the layer lowering the probability to generate C-N bonds. The composition of the plasma phase has therefore and logically a strong influence on the layer growth but, from our set of data, it appears that it is necessary to consider additional rearrangements in the layer to explain the higher content of some chemical groups (e.g. alkyne) in the film whereas this content is lower in the gas phase, when comparing the two precursors.

Resume : Since the 1980s, NH2-based plasma polymer films (NH2-PPF) attract a considerable attention owing to their promising use in a broad range of modern technological applications. To date, the biggest part of the research in this field has been dedicated to the control of the chemistry of the NH2-PPF. Nevertheless, it has recently been shown that besides the optimization of the chemical composition, structuring the NH2-PPF at the nanoscale can be of a real benefit for applicative purposes as for instance in the biomedical field (e.g., development of biosensors). In this context, here, we report on an original three-step approach combining several plasma-based methods to nanoengineer NH2-PPF. At first, NH2-PPFs are synthesized by PECVD (“Plasma Enhanced Chemical Vapor Deposition”) in a C2H2/NH3 mixture. In a second step, silver nanoparticles, employed as a hard-mask, are deposited on top of the NH2-PPF films by magnetron sputtering. The surface nanoengineering of the layers is achieved by a plasma-based etching process in Ar/N2/H2 gas mixture resulting in the formation of NH2-PPF nanopillars with a length of about 50 nm. The SEM micrographs and AFM measurements reveal that the diameter and the density of the NH2-PPF nanostructures are governed by the characteristics (e.g., shape, size and density) of the silver nanoparticles forming the hard-mask. The advanced understanding gained in this work enables to modulate in a wide range the structure of NH2-PPF at the nanoscale.

Resume : Recently, the epoxy surface functionalization gain considerable interest thanks to the easy, efficient one-step covalent binding of biomolecules induced by a rapid reaction between epoxy and amine groups, including primary, secondary and even tertiary amines. Nevertheless, there are just few papers dealing with the deposition of epoxy layer by plasma polymerization, although some promising results were obtained by plasma polymerization of glycidyl methacrylate. Unfortunately, this compound was found to be highly toxic. The plasma polymerization of non-toxic ally glycidyl ether (AGE) was pioneered by Thierry et al. However, the reported high thickness loss (40%, after 24 h in methanol) of AGE plasma polymers would be a problem for bio-application of these layers. In this work the low pressure plasma polymerization of AGE is thoroughly studied. Different discharge parameters including plasma power (P), duty cycle (D.C.), monomer flowrate (F) and pressure are varied in order to optimize the conditions for deposition of stable epoxy-rich layers. The IR spectroscopy, chemical derivatization and X-ray photoelectron spectroscopy were employed to characterize layer chemistry, whereas the spectroscopic ellipsometry was used for the determination of the layer thickness. Analyses revealed that the influence of duty cycle, power and AGE flowrate can be summarized by a macroscopic parameter W/F=P*D.C./F. The AGE fragmentation is increasing with W/F. The retention of epoxy groups increases by a factor of 4 (up to 3 carbon %), when the pressure is increasing from 10 to 50 Pa.. At the optimized condition, the density of epoxy groups and the thickness loss are 2 carbon % and <10%, respectively.

Resume : Since the eighties, functionalized plasma polymer films attract a considerable attention owing to their potential in a wide range of applications. For such materials, controlling the chemistry of the coatings by a clever choice of the process parameters represents the main challenge. Through the years, it became quickly obvious that, in view of the complexity of the growth mechanism, a fine control of the layers properties can only be reached by understanding, at a fundamental level, the mechanistic formation of the layers. In this context, a detailed comprehensive study of the plasma chemistry is therefore of crucial importance as the numerous interlinked chemical reaction occurring in the discharge govern the film properties. In this presentation, we review our recent efforts to contribute towards a better understanding of the plasma polymerization chemistry by using state-of-the-art diagnostic tools such as Mass Spectrometry and in-situ Fourier Transform Infrared Spectroscopy. In addition, we describe how theoretical calculations based on Density Functional Theory (DFT) can help for a better understanding of the acquired data.

Resume : Electrospun nanofibers are promising materials for tissue engineering thanks to their architecture analogous to the natural environment of tissue in physical structure and biological function. However, nanofibers prepared from biodegradable polymer polycaprolactone (PCL) are hydrophobic, which strongly decrease their biocompatibility. Therefore, a surface modification of the nanofibers is required in order to increase the wettability by introducing reactive groups (carboxyls, amines, anhydrides, etc.). In this work the deposition of the reactive anhydride groups was performed by co-polymerization of maleic anhydride and acetylene using atmospheric pressure dielectric barrier discharge (DBD). The discharge was operated in optically homogeneous mode in order to achieve homogeneous deposition and to minimize a damage of nanofibrous PCL substrate. At optimized conditions the DBD allowed the deposition of stable coatings onto the PCL nanofibers in the whole volume of the mesh while the structure of nanofibers was not damaged. Anhydride groups were chemically derivatized with trifluoroethylamine and plasma coating homogeneity was studied by scanning electron microscopy and secondary ion mass spectrometry imaging. Chemistry of the coating was investigated by means of infrared and X-ray photoelectron spectroscopies. The concentration of deposited anhydride groups was determined of up to 8.3 per 100 carbon atoms.

Resume : Surface plasmon resonance (SPR)-based methods are currently among the best choice to assess bioaffinity interactions at interfaces due to their sensitivity to local changes in the refractive index to adjacent media. From last decades, studies concerning the preparation of the SPR sensor focused on “bifunctional surface properties”: enhancement of the specific recognition of a biomolecule and avoidance of the nonspecific adsorption of other compounds. To fulfil these two objectives, scientists were mainly using self-assembled monolayers, which are sometimes quite unstable. As plasma deposition can provide highly stable polymer films, this technique appears to be suitable to prepare micropatterned films for sensing purposes. In this study, we propose a novel functional coating formed by a first amino-containing PPF layer, and a second carboxylic acid-containing PPF that is deposited through a mask. By this way, spatial localization of the second coating is controlled. Coating was then characterized by different analytical techniques (SEM, XPS, WCA). The use of a fluorescent protein highlighted the presence of the micropatterning, and of the two functionalities.