Protective coatings and thin films

Resume : Zirconium nitride (ZrN) coatings due to its inherent high hardness, wear resistance, corrosion resistance and gold like colour have attracted many applications ranging from coatings for wear resistance, corrosion resistance, coatings for biomedical appliances, high reflectivity optical and decorative surfaces. ZrN coating properties have shown a strong relationship with their employed techniques of growth process. Reactive Bipolar Pulsed Dual Magnetron Sputtering (BPDMS) is a powerful technique for the deposition at high deposition rate of dense and defect free coatings. Operating in the mid-frequency range the periodic target voltage reversals suppress arcing and stabilize the reactive sputtering process. Despite the success of the dual bipolar process, there are many aspect of this complex process that are not yet well understood, particularly the interrelationships between target voltage waveforms and plasma parameters and their impact on film growth. We studied the effect of BPDMS from a Zr target on structural and mechanical properties of the deposited ZrN films. We found that the hardness increases with decreasing of grain size and increasing packing factor. For BPDMS with 80 kHz and increasing duty cycle duration from 20 to 80 % the structure changes from a (111)-preferential oriented to random oriented single-phase cubic, resulting in hardness increases from 20 to 32 GPa, respectively.

Resume : Nanoporous materials exhibiting a sponge-like structure have recently revealed enhanced properties compared to their solid counterparts. Dealloying, which is an ancient alchemy technique used in the past in depletion gilding for the surface enrichment of artifacts of gold alloys, is among the most popular methods employed to create nanoporous materials. Currently, the conversion chemistry of such process has attained enough maturity to start concentrating the efforts on the integration of this promising class of materials in practical applications. An elegant way to achieve this goal is by using thin films technology. In this work we shed the light on a novel approach to synthesize nanoporous thin films of various materials (e.g., carbon and gold) exhibiting a sponge-like structure. Such process consists in the growth of binary alloy [1] or nanocomposite [2] thin films by co-sputtering followed by a free-corrosion process in nitric acid. We explore the impact of the composition, the structure and the morphology of the as-grown thin film precursors on the dealloying process as well as on the final porosity and crystalline structure of the nanoporous films. Based on our experimental observations, a scenario is further proposed to provide a detailed explanation of the fundamental mechanisms occurring during the dealloying process of films with various structures. [1] El Mel et al, ACS Appl. Mater. Interfaces, DOI:10.1021/am5065816 [2] Bouts et al, Carbon 83, 250, 2014

Resume : Requirements for tribological protective coatings for medical tools, which would increase their wear and corrosion resistance, particularly are very high. The presented paper deals with the novel nanocomposite, multilayer protective coatings for tissue interaction elaboration and their diagnosis on metallic substrates. A hybrid PLD system was used for coatings deposition. In the presented work, nano- composite, Cr/CrN+[Cr/ a-C:H implanted by metallic nanocrystals] multilayer coatings have been developed for surface protection. The mechanical properties of the coatings were investigated by means of micro- hardness and elasticity modulus measurements. Bio- medical tests were done using eukaryotic cells. Microstructure analysis by TEM indicated that chromium which was implanted into a-C:H layers reacted with carbon forming chromium carbides. Carbides were distributed in the a-C:H structure as nano- multilayers.

Resume : This study presents the bacterial reduction by visible light absorbing nanocomposite stable, resistant and non-corrosive oxynitrides films presenting absorption in the visible spectral range and their silver derivatives. The design, sputtering, bacterial evaluation and surface characterization of uniform and adhesive nanoparticulate oxynitrides films is described in detail. The bacterial reduction was observed by these Ag- oxynitrides in the dark and with high kinetics under daylight/actinic light irradiation. The special interest for the oxynitrides is their low cytotoxicity and chemical stability, making them suitable as supports for highly oxidative Ag-nanoparticles. The Ag-TiON fast inactivation kinetics concomitant with low cytotoxicity, low cost and long operational lifetime are the essential requirements for the potential practical application of these antibacterial surfaces. The aim here is to show the bacterial inactivation as a function oxynitride composition and details of the microstructure and properties by up-to-date surface characterization techniques.

Resume : Quaternary TiZrAlN and TiZrSiN films were grown at Ts=600 °C by reactive magnetron sputtering in Ar+ N2 plasma discharge from elemental targets. Deposition occurred at the constant power of Ti and Zr targets, while changing the Al (resp. Si) power and adjusting the N2 flow rate, resulting in stoichiometric nitride films (N concentration between 48 and 53 at.%) with Al (resp. Si) content up to 23 at.% (resp. 13 at.%) and fixed Zr :Ti ratio of 1.1. It is shown that single-phase, cubic (Ti,Zr)1-xAlxN solid solutions are stabilized upon incorporation of Al, while dual-phase, nanocomposite TiZrSiN films consisting of cubic TiZrN grains surrounded by SiNy phase are formed upon incorporation of Si. The lattice parameter of Al-containing films linearly decreases with the increase in Al concentration. During vacuum annealing (up to 1000 °C), the subsequent increase in the lattice parameter can be connected with out-diffusion of Al from c-TiZrAlN phase. The lattice parameter of Si-containing films is close to that of pure TiZrN film. The phase composition of TiZrSiN films is stable under vacuum annealing, except above 1000°C where a weak ZrN (200) reflection appears, indicating that structural phase transformation occurred. Both TiZrAlN and TiZrSiN films are under compressive stress state (up to -2 GPa). For these films the maximum hardness, 25 GPa (resp. 29 GPa) is achieved at Al content of 19 at.% (resp. Si content of 6 at.%).

Resume : Keywords : hard thin films, oxidation, microstructure, SEM, TEM, in situ approach, micro-tensile tests, Digital image correlation New economical and ecological tendencies in the industrial area yield to increase machining speeds together with a drastic restriction of lubricant-cooling fluids. As a consequence, the surface of coated tools has to withstand extreme conditions, especially in terms of temperature, which can locally reach 1000°C, and severe deformation. Simple transition metals nitrides cannot sustain such extreme conditions. Therefore, a new generation of coating enriched in aluminium, as it is the case for AlTiN and AlCrN, and reactive elements, such as yttrium to form CrAlYN or AlTiYN, has been developed. The aim of this talk is to characterize at a fine scale and in situ the damage linked to an important controlled deformation of the surface, and to determine its consequences regarding the oxidation behavior. Influence of the microstructure and of yttrium incorporation is studied through a metallurgical and micro-mechanical approach. 3 µm-thick films were synthesized by arc-evaporation of Al60Cr40 and Al59.1Cr30.4Y1.5 targets into a PVD random arc reactor, using a constant evaporation intensity of 80 A. Deposition was conducted for a bias voltage applied in the range of -30/-60 V at a deposition pressure of 3 Pa. Surface defects are observed using SEM, TEM and quantitatively determined by electrochemistry. Residual stresses of films are measured through XRD measurements using the sin2 psi method. Of prime interest is the cracking behavior, investigated at a deep-scale through a micro-tensile test machine able to be implemented into the SEM chamber. The dynamic of the surface is got through a specific DIC (Digital Image Correlation) post-treatment. Deformation behaviors are then discussed in light of chemistry, residual stresses and microstructure of films.

Resume : Accurate characterization of the mechanical properties of superhard, nanocomposite thin films is particularly complicated, but it is crucial since these nanomaterials attract the interest of the scientific community and meet the needs of the protective coatings industry. In this paper, we focus on the accurate nanomechanical characterization of superhard Ti-B-N nanocomposite thin films using depth-sensing nanoindentation and atomic force microscopy (AFM). Nanoindentation was performed using two Berkovich (triangular-pyramid) type diamond indenters with different tip roundness (nominal tip roundness 20 nm and 50 nm), while the AFM was used to image the nanoindentation imprints and to study the difference in the deformation induced to the superhard films by the two different Berkovich diamond tips. The sharper diamond tip was found to induce elastic/plastic deformation at swallower depth (~10 nm), fact that enables the measurement of the hardness (H) and the elastic modulus (E) closer to the thin film surface. In addition the analysis of the nanoindentation load-displacement curves showed that both the H and E values were found to be considerably higher in the case of the sharper tip (e.g. 52 GPa against 31 GPa for the H in the case of the most promising sample). Finally, the mechanical properties were correlated with the thin film structure coming from the X-rays characterization. Acknowledgments: Hellenic National Strategic Reference Framework 2007?2013, contract no. 11ΣΥΝ-5-1280, Project ?Nano-Hybrid?, within the Program ?Competitiveness and Entrepreneurship?.

Resume : In this work, the evolution of the structure and morphology of Sn4Sb6S13 thin films grown by thermal evaporation was investigated .The films were deposited onto glass substrates heated in the temperature range 30-200°C.The deposited films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Scanning electron microscopy (SEM), Homogeneous films were found to be preferentially orientated along the ((6 ) ̅11) direction. The surface morphological analysis revealed that the films had an average roughness increase from 0.58 to 6.45 nm with increasing the substrate temperature from 30 to 200 °C. The variations of the microstructural parameters, such as crystallite size (D), dislocation density (δ), stacking fault probability (α) and strain (ε) with substrate temperature were investigated. FTIR and Raman were used to obtain information about structural changes of Sn4Sb6S13 films.

Resume : Owing to outstanding characteristics of carbon nanotubes (CNTs) such as small size, large surface area, hollow geometry, and highly sensitive electrical properties, CNTs have been widely used in a variety of devices and systems. We have prepared metal-CNTs core-shell nanostructures by sputtering technique with the metal target, subsequently investigating the effects of thermal annealing. The surface of metal-CNTs became rougher by the thermal annealing, being attributed to the agglomeration of the metal shell layers into the metal oxide (MOx) nanoparticles. The gas sensing test demonstrated that the MOx functionalization significantly improved the sensing performances, successfully attaining the higher sensitivity and faster response than bare CNTs. We have scrutinized the possible mechanisms for improvement of the sensing properties by MOx-functionalization.

Resume : The optical confinement is an important parameter for enhancing the efficiency of solar cells. In this context, transparent conductive oxide coating (TCO) with randomly textured surfaces is widely used to improve optical confinement, where many numerical and experimental studies have been carried out to investigate the impact of the surface texture morphology on the electrical performance of the solar cell. However, till now, any analytical investigation is proposed to optimize and improve the electrical efficiency of SiGe-based solar cells, taking into account the texture morphology effects. In this paper we present an analytical investigation including texture morphology effects, in order to optimize the texture morphology and TCO design parameters. In the present paper, we propose an analytical model allowing the electrical efficiency optimization for Glass/ZnO:Al/SiGe/Si heterojunction solar cell, by taking into account the surface texture morphology, Al concentration and Ge mole fraction effects. A multi-objective genetic computation has been used to optimize triangular grating. Solar cell with optimized triangular grating exhibits an enhancement over planar and randomly triangular grating cells. The purpose of this work is to formulate novel design criteria based on analytical and optimization investigation of surface texture morphology that would help in obtaining a high electrical performance.

Resume : Cobalt-chromium (CoCr) alloys and austenitic stainless steels (ASSs) are the most suitable metallic biomaterials owing to their good wear and corrosion resistance, and sufficient biocompatibility. However, there are concerns over the wear of such biomaterials surfaces and toxic metal ions release when they are used as medical implants. Low temperature plasma assisted nitriding is an effective treatment that improves wear and corrosion resistance, and reduces the release of potentially harmful metal ions from these alloys. Expanded austenite phase, formed after plasma assisted nitriding of CoCr base alloys and ASSs, is characterized by the expansion of the alloy lattice and an anomalous diffusion of nitrogen. In this work the nitrogen diffusion in CoCr alloy and ASS is investigated on the basis of internal stress assisted diffusion model. Proposed model assumes that the stress field, associated with the distorted alloy lattice due to incorporation of nitrogen, effects the diffusive flux of nitrogen. It was shown, that the enhanced nitrogen diffusivity in the expanded austenite as well as a plateau-type shape of nitrogen depth profile can be explained by proposed model.

Resume : TTMS has been used to study plasma enhanced chemical vapor deposition processes at atmospheric pressure (AP-PECVD). TTMS has been chosen because of its potential to form branched organosilicon polymers of regular structure that is used in the chemical synthesis. Despite the widespread surveying of various silicon-organic molecules for PECVD, the use of TTMS in AP-PECVD has not been investigated deeper yet. Deposited films based on TTMS exhibit diametrically opposed morphology from closely spaced smooth films to nano-dendriticaly branched 3D structures depending on the particular process. AP-PECVD processes have been performed with two different plasma jets. While they are alike regarding the geometry and injection of TTMS, they differ in electrical power and excitation frequency. The radiofrequency plasma (RF) jet [1] operates at lower power densities as compared to the microwave plasma (MW) jet [2]. For all observed film morphologies, from amorphous, smooth films to films with dendritic structure, the results of the surface and film analysis (X-ray photoelectron spectroscopy and FTIR absorption) demonstrate their inorganic character. The carbon content does not exceed 5% while the IR absorption band of OH remains below the detection limit. The stoichiometry resembles that of silicon dioxide (Si:O=1:2). Supported by DFG TRR 24. [1] J. Schäfer et al., Plasma Phys. Control. Fusion 51, 12, 124045, 2009. [2] J. Hnilica et al., J. Phys. D: Appl. Phys. 45, 5, 055201, 2012.

Resume : Perovskite materials with ABO3 formula present interesting properties depending on their composition, and are studied for their potential applications as smart or monitoring devices. Some of these perovskites based on iron and Rare Earth elements are particularly adapted as NOx gas sensors, or fuel cells electrodes, and the requirement of miniaturization and low power consumption in such electronic components has led to the development of thin films. The understanding of their growth and crystallization mechanisms are thus important to optimize their properties. In this work, we investigate crystallization mechanisms of REFeO3 (RE= La, Pr, Nd, Sm) thin films. Films were deposited by magnetron sputtering, from two metallic targets (RE and Fe), in reactive atmosphere (Argon + Oxygen), onto (100) undoped Si single-crystal. The deposition temperature was fixed at 400°C to avoid stresses and crystallization start. The chemical stoechiometry of these films was checked by energy X-ray analyses (EDS). As grown films were amorphous and crystallization was induced by heating it in a furnace. This crystallization develops during heating and this evolution was characterized by in situ XRD measurements. We have used Johnson-Mehl-Avrami-Kolmogorov (JMAK) model to quantify the kinetic crystallization of films. In a first step, XRD measurements were performed at different temperatures, to approximately determine the crystallization temperature. Secondly, XRD measurements were performed on a restricted diffraction angle range, to record area of (121) peak as a function of time. The peak area is linked to the crystallized fraction inside the film. Then, JMAK equations have been applied to find crystallization mechanisms, depending on Avrami parameters. Finally, Arrhenius law was used to calculate rate constant and activation energy of the crystallization reaction. We observe a constant increase of the energy required to crystallize the perovskite by decreasing the ionic radius of the Rare Earth element.

Resume : Carboxyl coatings are extensively used for adhesion promotion, bio-immobilization, surface reactions, thanks to their reactivity towards nucleophilic groups and high wettability. The deposition of relatively stable carboxyl-rich coatings using low-cost atmospheric pressure plasma processes was achieved by copolymerization of acrylic acid and ethylene or maleic anhydride and vinyltrimethoxysilane. The acrylic acid or maleic anhydride provide a reactive carboxyl group, while layer crosslinking is enhanced by adding a second monomer. The detailed research of the thickness loss and the retention of carboxyl function after immersion of such copolymers in water is not available in the literature. This work is aimed at the investigation of the plasma copolymerization of maleic anhydride and acetylene by atmospheric pressure dielectric barrier discharge. The quantification of the carboxyl groups was performed by X-ray photoelectron spectroscopy (XPS) C1s curve fitting and by derivatization with trifluoroethanol. The layer synthesized at optimized monomer flow rate and plasma power, contained 5 at% of COOH groups (determined by derivatization combined with XPS) and exhibited the thickness loss below 10% after 128 hours in water. The influence of plasma chemistry, gas dynamics and plasma power on the layer properties was studied. Numerical models were developed to understand the importance of the gas dynamics in the deposition process and optimize the set-up.

Resume : Raney type nickel alloys with high surface area and specific morphology are promising catalysts for low-temperature fuel cells, particularly alkaline and urea fuel cells. Our research focuses on improving the catalyst performance by controlling the shape and size of the nickel nanostructure. In this respect, we use thermionic vacuum arc deposition to produce Ni - Al thin films; the method employs two independent and constant electron beams emitted by externally heated cathodes inside a vacuum chamber. The resulting Ni - Al films are thermally treated at high temperatures, then activated with concentrated sodium hydroxide, which also results in aluminum leaching from the alloy. The aim of this work is to investigate skeletal nickel catalysts incorporation in alkaline fuel cells. The Raney type Ni nanostructures are evaluated by scanning electron microscopy and electrochemical methods; the prototype catalysts are then tested in an alkaline fuel cell.

Resume : In this study selective permeability of poly(hydroxyethylmethacrylate), p(HEMA), thin film membranes are investigated. P(HEMA) free standing thin films with different crosslink ratios are synthesized via initiated chemical vapor deposition (iCVD). Dependence of swelling kinetics on the chemical composition of the films is studied by spectroscopic ellipsometry and Fourier transform infrared spectroscopy. Selective permeation of dyes with different size and hydrophilicity through the membranes is investigated via diffusion tests using a side-bi-side cell and UV-vis spectroscopy. Using the diffusion studies of the model dyes, the relation between the chemical composition and the permeability coefficients of the membranes is studied and methods to tailor the selectivity of the membranes by tuning the fabrication methods are discussed.

Resume : Multicomponent carbide coatings, containing transitional metals, with or without Si, are promising ceramic materials, exhibiting high hardness, low residual stress, improved corrosion resistance. An amorphous coating - (CuTiYSiZr)C, and three crystalline coatings - (CuTiYCrNb)C, (TiYCrNbAl) and ZrSiC, were analyzed in term of elemental composition and crystallographic structure. The surface and in-depths coating morphology was correlated with their tribological performance, assessed in terms of friction coefficients and wear rates. Compared to the stoichiometric coatings with columnar structures, the overstoichiometric ones present finer, denser, and almost glassy structures. The existence of the free-carbon phase in overstoichiometric coatings, evidenced by Raman and XPS analyses, determined a reduced surface roughness, with a reduced coefficient of friction (<0.2) and low wear rates (of about 10-6 m3N-1m-1). The tribological characteristics similarities noticed for all the investigated overstoichiometric coating indicated that the amorphous carbon phase plays a major role, out-shadowing the nature of other elements, as well as their number. The increase of carbon content in the coating to about 80% determined an accentuated decrease of the surface roughness (RMS < 2 nm), resulting in a further decrease of the friction coefficient to about 0.05.

Resume : Zr- and Cr- doped TiSiC coatings were deposited on Si and 316 L steel substrates by the cathodic arc technique using CH4 as reactive gas. Corrosion and wear tests in normal 0.9% NaCl solution were performed. Additional investigations on elemental composition, crystalline structure and surface morphology of the coatings were carried out. The following main conclusions are drawn from the experimental results of the present study. An overstoichiometric film composition was determined, with a C/ (metal Si) ratio of 1.5‒1.7 and added metal/Ti ratio of about 0.4‒0.5. All the coatings contained FCC nanocrystalline solid solution phases, with nanometer size crystallites (4.3‒7.1 nm). If compared to the 316 L steel substrate, the coatings exhibited superior corrosion behaviour. This fact is indicated by the more electropositive corrosion potential, the lower corrosion current densities and the higher polarization resistances. Combined effects of corrosive, adhesive and oxidative wear were considered to mainly contribute to coating damage under wear in corrosive environment. In the saline solution, the TiSiC-Cr coating was found to have better tribological performance than TiSiC-Cr coating, opposite to the results obtained in dry tribological tests. Therefore, for a proper selection of the alloying metal aiming to improve the performances of TiSiC protective coatings, one should consider the specific working conditions in the envisaged application.

Resume : Thin film metallic glasses are a new class of promising materials for advanced structural applications. In this work, binary Zr-based thin film metallic glasses (TFMGs) were deposited by the magnetron co-sputtering process from pure metal targets. Two similar enrichments were investigated (44 at.% for the nickel, 43 at.% for the cobalt), in order to determine the effect of the alloying element’s nature on the structural, mechanical and electrochemical behaviors. Structure of films was determined by in situ XRD measurements carried out during heating up to 600°C, while their morphology was characterized by SEM observations. Mechanical properties of amorphous and crystallized films (hardness and Young’s modulus) were measured by nanoindentation. Intrinsic electrochemical properties are deduced from polarization curves and electrochemical impedance spectroscopy measurements carried out in Na2SO4 aqueous solution. It is found that the surface morphology of TFMGs were very smooth with a compact and dense microstructure. When heated, glassy films exhibit a high structural stability (up to 440 °C) with crystallization occurring through a multistage process for the Co-containing film. Whatever the coating, Zr affords its beneficial passive-ability, while crystallization process accelerates the global corrosion kinetics. Corrosion mechanisms of the Zr-based TFMGs were discussed in the light of the alloying element (Ni or Co) and the structure of films (amorphous or crystallized).

Resume : The interest in nanocomposite materials containing those metal NPs embedded in dielectric matrices, such as TiO2 or Al2O3, is related with their potential use for a wide range of advanced technological applications, including colour filters, optical sensors, solar cells, photocatalytic antibacterial and pollutant-degradation materials, gas sensors and Surface Enhanced Raman Spectroscopy (SERS). Most of these applications, particularly, those in the decorative field, rely on the so-called localized surface plasmon resonance (LSPR) absorption, which is governed by the type of the noble metal NPs, their distribution, size and shape and as well as of the dielectric properties of the matrix. Results show that the annealing experiments enabled a gradual increase of the mean grain size of the Au NPs (from 2 to 23 nm), and changes in their distributions and separations within the dielectric matrix. For higher annealing temperatures of the as-deposited films, a broad size distribution of Au NPs was found (sizes up to 100 nm). The structural conditions necessary to produce LSPR activity were found to occur for annealing experiments above 300 ºC, which corresponded to the crystallization of the gold NPs, with an average size strongly dependent on the annealing temperature itself. The host matrix started to crystallize at an annealing temperature of about 500 ºC, which is an important parameter to explain the shift of the LSPR peak position to longer wavelengths, i.e. a red-shift.

Resume : Nanoparticles (NPs) of noble metals on surfaces or embedded in dielectric hosts give rise to interesting optical responses related to collective oscillations of free electrons. They lead to surface plasmon resonances (SPR) in the visible part of the spectrum that give rise to intense colours, thus becoming attractive for decorative coatings. One of their appealing properties is the possibility to tune the optical response or colour through parameters such as the size or shape of the NPs as well as their spacing or proximity. In this work we demonstrate that surface treatment of multilayer thin films (thickness <20 nm) with single UV nanosecond laser pulses is an easy-to-use tool for tuning the NPs optical response in a wide spectral range. We have selected a bilayer system (Au & Ag) on glass substrates and used single layers of Ag or Au for comparison. As film parameters, we have studied the deposition order and the composition by varying the thickness of the Au layer while keeping that of Ag constant. As laser parameter, we have varied the fluence. The samples are optically and structurally characterized by extinction spectroscopy and scanning electron microscopy, respectively. The laser treatment produces mixing of the two metals and NPs with a diameter that depends on the total amount of metal. Depending on fluence, the interparticle distance can become comparable to the NPs diameter and multipolar interactions dominate the optical response.

Resume : LaB6 is a refractory compound that is well known for its very low work function. It has been mainly used for electron emitting devices working at high temperatures in vacuum. We depos-ited LaB6 films on Si substrates at 500 deg. C under ultrahigh vacuum conditions using the pulsed laser deposition technique. The structure was investigated by grazing incidence and symmetrical X-ray diffraction. The use of a high laser fluence (~7 J/cm2) during deposition re-sulted in the synthesis of slightly textured films along (100) axis, with small crystallite sizes and rather high level of microstresses. X-ray reflectivity investigations showed that films were very dense and smooth, while X-ray photoelectron spectroscopy found that films were almost stoichiometric and contained a low amount of oxygen. Four point probe measurements showed that films exhibited very good electrical conductivity, below 100 micro-ohm.cm. Nanoindentation and scratch tests found that films were hard, adherent, and exhibited low friction coefficients. All these characteristics recommend the LaB6 films for usage as sliding electrical contacts operating under vacuum and/or extreme temperatures.

Resume : In order for thin film photovoltaic devices to contribute to future renewable energy generation they must consist of earth abundant materials and be cheap to manufacture. At the heart of thin film photovoltaic devices lies the p-type semiconductor absorber layer whose job is to convert incoming solar radiation into electrical charge carriers that are subsequently separated across the p-n junction. The leading earth abundant thin film absorber layer is Kesterite, Cu2Zn(Sn,Ge)(S,Se)4, which has produced laboratory scale power conversion efficiencies of around 12 %, close to the necessary efficiency for thinking about industrial production. Here, the current status of Kesterite technology will be reviewed in terms of desired and achieved properties and the synthetic challenges which must be overcome to improve overall device efficiency. Amongst the key semiconductor properties for thin film absorber layers are band gap, doping density and minority carrier life. Additionally, attention to layer integrity and the presence of detrimental secondary phases is of equal importance. The quaternary Kesterite has a rather small single phase region and multiple secondary phases are possible. Also, under normal synthesis conditions it releases two volatile species that must be taken into account for any controllable synthesis. Given these challenges, and with a perspective to depositing films on a meter squared basis, a close examination of Kesterite layer growth strategies is required.

Resume : III-V semiconductors represents ideal candidates for several applications. However, the spontaneous oxidation in air leads to the loss of its electrical properties. The surface passivation becomes a key step for its integration in attractive devices. In this work, the electrochemical passivation of III-V semiconductors is evidenced in liquid ammonia ( 55 °C) during an anodic treatment as alternative ways for nitrogen (N2+) ion bombardment procedure or N2 plasma technique. We reproducibly realized the formation of a polyphosphazene-like (H2N-P=NH)n film on InP. The monitoring of the film formation was performed using a systematic coupling between electrochemical measurements and X-ray photoelectron spectroscopy. Detailed analysis show the growth mechanism of the film starting from nucleis up to a complete coverage. The lowest charge required to guarantee full coverage of InP by the film is determined (~ 0.5mC/cm2) which shows that only some layers of InP are involved (density of surface atoms=1015/cm2). The study of the air ageing or the evolution in contact with strong oxidants of the modified surface revealed the chemical protection of the surface by the film. This tremendous stability is also in accordance with the high level of luminescence. PL measurements show that really few interface states are created upon film formation. Promisingly, the film prevents the decrease of luminescence in long periods of time suggesting the maintaining of a good interface.

Resume : Nowadays there is a strong belief that thermoelectric thin film-based devices represent a suitable route to mitigate thermal management problems in micro- and nano-electronics. Bi0.5Sb1.5Te3 is considered to be a state-of-the-art p-type thermoelectric material, at temperatures near room temperature, due to its high power factor value. We have grown p-type Bi0.5Sb1.5Te3 thin films onto different types of substrates using pulsed laser deposition at 248nm and home-made targets with different Bi concentrations, and investigated their structural, electrical and thermoelectrical properties. In this talk, we will present our recent results on Seebeck coefficient, electrical resistivity and Hall carrier concentration as a function of temperature for a series of Bi0.5Sb1.5Te3 thin films. We will discuss how their thermoelectric properties are affected by the substrate type and Bi content. Also, we will address the effect of post-annealing treatment on their structural and thermoelectric properties.

Resume : Non-thermal atmospheric pressure plasmas (APPs) have attracted great interest due the potential cost reductions in manufacturing and processing of materials for a wide range of applications. Although APPs present several challenges, considerable progress has been achieved in recent years with an increasing number of industrial and commercial applications utilizing different forms of APPs. One of the most attractive applications of APPs is for the synthesis and processing of nanomaterials with specific focus on materials for energy applications. In this contribution we will present recent advances in both the synthesis and surface engineering of a range of materials including metal, metal-oxides and quantum confined silicon-based nanoparticles. We will then discuss the integration of such materials and low-cost APP-based processes for the fabrication of photovoltaic devices, demonstrating their contribution and potential for an all-APP fabrication sequence. Device parameters will be presented and analysed for different device architectures. Finally, we will show also how APP-based surface engineering can also offer great opportunities for tailoring surface properties of nanoparticles and contribute to further our scientific understanding of nanosystems.

Resume : Stable amine-rich plasma coatings have numerous important applications including cell adhesion enhancement and biomolecule immobilization. The bioapplication of plasma coatings requires sufficient layer stability in water in order to avoid leaching of toxic oligomers and increase the durability of the deposited coating. For majority of monomers used for plasma polymerization of amine coatings (allylamine, ethylemediamine, ammonia/ethylene), the increase of the coating stability was obtained at the expense of the surface concentration of amines. Recently, it was found that amine-rich cyclopropylamine (CPA) plasma polymers exhibited extremely low thickness loss (1-2%) combined with 9 at.% of NHx environment if the substrate is DC self-biased. Hence, the stability was sufficiently improved compared to previous results (thickness loss of 20%, NHx of ~10 at.%) where the substrate was at a floating potential. The IR spectroscopy and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) combined with principal component analysis (PCA) were employed to investigate the crosslinking degree of the CPA plasma polymers. According to IR data, the layers deposited at floating potential exhibited higher intensities of nitriles and lower intensities of hydrocarbons. PCA analysis of ToF-SIMS data revealed that the layers deposited at DC self-bias has higher C/H ratio and therefore, higher crosslinking degree. Hence, the deposition at DC self-bias allowed to improve the layer stability without large sacrifice of the amine concentration.