Aluminium-doped ZnO (AZO) thin films were deposited by remote plasma sputtering of a ZnO:Al2O3 98:2 wt% ceramic target in a pulsed DC configuration. The target power was kept constant at 445 W and the RF plasma power was varied between 0.5 and 2.5 kW. The as-deposited AZO thin films exhibited an optimum resistivity of 6.35 x 10(-4) omega.cm and optical transmittance of 92% at a RF plasma power of 1.5 kW. The thin film microstructure, chemical composition, and residual stress were investigated using SEM, RBS, XPS and XRD. Accurate determination of the chemical composition and correct interpretation of GIXRD data for AZO thin films are a particular focus of this work. The AZO layer thickness was 500-700 nm and Al content in the range of 2.3-3.0 at.%, determined by RBS. The AZO thin films exhibited a strong (002) preferential orientation and grain sizes between 70 and 110 nm. The (103) peak intensity enhancement in GIXRD is proven to be a result of the strong (002) preferential orientation and GIXRD geometrical configuration rather than a change in the crystallite orientation at the surface. XPS depth profiles show preferential sputtering of O and Al using a 500 eV Ar+ beam, which can be reduced, but not eradicated using an 8 keV Ar-150(+) beam. The preferential sputtering can be successfully modelled using the simulation software TRIDYN. A plasma power of 1.5 kW corresponds to a highly ionised plasma and various microstructural and compositional factors have all contributed to the optimum low resistivity occurring at this plasma power. The grain size exhibits a maximum in the 1.25-1.5 kW range and there is improved (002) orientation, minimising grain boundary scattering. The highest carrier concentration and mobility was observed at the plasma power of 1.5 kW which may be associated with the maximum in the aluminium doping concentration (3.0 at.%). The lowest residual stress is also observed at 1.5 kW.

Ultra-thin CdTe:As/Cd1-xZnxS photovoltaic solar cells with an absorber thickness of 0.5 mu m were deposited by metal-organic chemical vapour deposition on indium tin oxide coated boro-aluminosilicate substrates. The Zn precursor concentration was varied to compensate for Zn leaching effects after CdCl2 activation treatment. Analysis of the solar cell composition and structure by X-ray photoelectron spectroscopy depth profiling and X-ray diffraction showed that higher concentrations of Zn in the Cd1-x..,,ZnxS window layer resulted in suppression of S diffusion across the CdTe/Cd1-xZnxS interface after CdCl2 activation treatment. Excessive Zn content in the Cd1-xZnxS alloy preserved the spectral response in the blue region of the solar spectrum, but increased series resistance for the solar cells. A modest increase in the Zn content of the Cd1-xZnxS alloy together with a post-deposition air anneal resulted in an improved blue response and an enhanced open circuit voltage and fill factor. This device yielded a mean efficiency of 8.3% over 8 cells (0.25 cm(2) cell area) and best cell efficiency of 8.8%. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license

Ultra-thin CdTe photovoltaic solar cells with an absorber thickness of 0.5μm were produced by metal organic chemical vapour deposition onto indium tin oxide coated boroaluminosilicate glass. A wide band gap Cd1−xZnxS alloy window layer was employed to improve spectral response in the blue region of the solar spectrum. X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy were used to monitor changes in the chemical composition and microstructure of the Cd1−xZnxS/CdTe solar cell after varying the post-deposition CdCl2 activation treatment time and annealing temperature. The CdCl2 treatment leached Zn from the Cd1−xZnxS layer causing a redshift in the spectral response onset of window absorption. S diffusion occurred across the Cd1−xZnxS/CdTe interface, which was more pronounced as the CdCl2 treatment was increased. A CdTe1−ySy alloy was formed at the interface, which thickened with CdCl2 treatment time. Small concentrations of S (up to 2at.%) were observed throughout the CdTe layer as the degree of CdCl2 treatment was increased. Greater S diffusion across the Cd1−xZnxS/CdTe interface caused the device open-circuit voltage (Voc) to increase. The higher Voc is attributed to enhanced strain relaxation and associated reduction of defects in the interface region as well as the increase in CdTe grain size.

In this paper the low temperature deposition of nanocrystalline and ultrananocrystalline diamond (UNCD) films is compared and discussed. NCD films were prepared by hot filament chemical vapor deposition from a 1% CH4/H2 mixture, while microwave plasma chemical vapour deposition was used to deposit UNCD films from a mixture of 17% CH4/N2. The resulting films have been thoroughly characterized concerning their morphology and structure by scanning electron microscopy and concerning their crystalline properties by X-ray diffraction. The composition was analyzed by X-ray photoelectron spectroscopy (XPS), whereas XPS and Raman spectroscopy were applied to get information on the bonding structure of the films. The most important result of this study is that the composition, structure, morphology, and bonding environment of UNCD hardly change if the deposition temperature is lowered from 770 to 530 degrees C or even 450 degrees C. In contrast, there are drastic changes of the nature of NCD films if the temperature is reduced to 700 degrees C or even lower. Interestingly, the sp2/sp3 ratio of the NCD films remains low and constant in the temperature range investigated. Rather, the nature of the sp2 grain boundary material undergoes drastic changes if the temperature is lowered below 700 degrees C. In addition, the films become inhomogeneous on a micrometer (not nanometer) scale. Possible reasons for these observations will be discussed throughout the paper.

This paper presents results on the PVD CrCuN nanocomposite coating system, in which the immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or β-Cr2N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by XPS, TEM, SEM and XRD. Hardness, wear resistance and impact resistance have been determined by nanoindentation, reciprocating-sliding and ball-onplate high-frequency impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprising of 1-3 nm -Cr(N) and β-Cr2N grains separated by intergranular regions of Cu give rise to a coating with significantly enhanced resistance to impact wear.

TiAlBN coatings have been deposited by electron beam (EB) evaporation from a single TiAlBN material source onto AISI 316 stainless steel substrates at a temperature of 450°C and substrate bias of −100V. The stoichiometry and nanostructure have been studied by X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron microscopy. The hardness and elastic modulus were determined by nanoindentation. Five coatings have been deposited, three from hot-pressed TiAlBN material and two from hot isostatically pressed (HIPped) material. The coatings deposited from the hot-pressed material exhibited a nanocomposite nc-(Ti,Al)N/a-BN/a-(Ti,Al)B2 structure, the relative phase fraction being consistent with that predicted by the equilibrium Ti–B–N phase diagram. Nanoindentation hardness values were in the range of 22 to 32GPa. Using the HIPped material, coating (Ti,Al)B0.29N0.46 was found to have a phase composition of 72–79mol.% nc-(Ti,Al)(N,B)1−x+21–28mol.% amorphous titanium boride and a hardness of 32GPa. The second coating, (Ti,Al)B0.66N0.25, was X-ray amorphous with a nitride+boride multiphase composition and a hardness of 26GPa. The nanostructure and structure–property relationships of all coatings are discussed in detail. Comparisons are made between the single-EB coatings deposited in this work and previously deposited twin-EB coatings. Twin-EB deposition gives rise to lower adatom mobilities, leading to (111) (Ti,Al)N preferential orientation, smaller grain sizes, less dense coatings and lower hardnesses.

Cu–Cr–N coatings with Cu contents between 3 and 65 at.%, Cu/Cr ratios in the 0.04–4.5 range and 21–27 at.% N, synthesized by twin electron-beam Physical Vapor Deposition at 450 °C, were investigated and compared against substoichiometric Cr–N reference samples. The main objective of this study is to study the influence of Cu on the structure, and the subsequent effects on the mechanical properties, room (22 °C) and high temperature (500 and 840 °C) tribological performance of Cu–Cr–N coatings. Using X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and scanning electron microscopy, in combination with nanoindentation mechanical property measurements and laboratory-controlled ball-on-disc sliding experiments, it is shown that Cu–Cr–N coatings with low Cu content (3 at.%) possess sufficient wear resistance for high-temperature demanding tribological applications. The lubricious effect of oxide formation at high temperatures is also evaluated.

gamma-Al2O3 is a well known catalyst support. The addition of Ce to gamma-Al2O3 is known to beneficially retard the phase transformation of gamma-Al2O3 to alpha-Al2O3 and stabilize the gamma-pore structure. In this work, Ce-doped gamma-Al2O3 nanowires have been prepared by a novel method employing an anodic aluminium oxide (AAO) template in a 0.01 M cerium nitrate solution, assisted by urea hydrolysis. Calcination at 500 degrees C for 6 h resulted in the crystallization of the Ce-doped AlOOH gel to form Ce-doped gamma-Al2O3 nanowires. Ce3+ ions within the nanowires were present at a concentration of <1 at.%. On the template surface, a nanocrystalline CeO2 thin film was deposited with a cubic fluorite structure and a crystallite size of 6-7 nm. Characterization of the nanowires and thin films was performed using scanning electron microscopy, transmission electron microscopy, electron energy loss spectroscopy, x-ray photoelectron spectroscopy and x-ray diffraction. The nanowire formation mechanism and urea hydrolysis kinetics are discussed in terms of the pH evolution during the reaction. The Ce-doped gamma-Al2O3 nanowires are likely to find useful applications in catalysis and this novel method can be exploited further for doping alumina nanowires with other rare earth elements.

This paper reports on the structure and mechanical properties of ~ 2 μm thick nanocomposite (nc-) Ti(N,C)/amorphous diamond like carbon (a-C:H) coatings deposited on 100Cr6 steel substrates, using low temperature (~ 200 °C) DC reactive magnetron sputtering. The carbon content was varied with acetylene partial pressure in order to obtain single layer coatings with different a-C:H carbon phase fractions. The nanocrystalline Ti(N,C) phase is approximately stoichiometric for all coatings and the a-C:H phase fraction increases from 31 to 47 at.% as the coatings stoichiometry changed from TiC1.34 N0.51 to TiC2.48 N0.48, respectively. TiC1.34 N0.51 coatings showed the highest nanoindentation hardness (H) of ~ 14 GPa and a modulus (Er) of ~ 144 GPa; H reduced to < 6 GPa and Er to < 70 GPa for TiC2.48 N0.48 coatings. nc-Ti(N,C)/a-C:H coatings are promising candidates for applications where better matching of the modulus between a relatively low modulus substrate, hard loading support layer and low modulus-high H/E ratio top layer is required.

Cr-N and Cu-Cr-N coatings with Cu content between 3–65 at.%, Cu/Cr ratios in the 0.04–4.5 range and 21–27 at.% N, synthesized by twin e-beam Physical Vapor Deposition (EBPVD) at 450°C, were investigated. Using X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GAXRD) and scanning electron microscopy (SEM), in combination with nanoindentation mechanical property measurements and laboratory controlled ball-on-disc sliding experiments, it is shown that Cu-Cr-N coatings with low Cu content (3 at.%) possess sufficient wear resistance for high temperature demanding tribological applications.

Tantalum pentoxide (Ta2O5) thin films have been deposited at room temperature by single and dual ion beam deposition (IBS and DIBS, respectively) for applications as a waveguide in biosensors. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction have been employed, among others, to establish composition, bonding structure and crystallinity of the films. The optical properties were established by variable angle ellipsometry, UV/VIS spectroscopy and direct measurements of the optical losses. Provided the oxygen partial pressure during deposition is high enough, stoichiometric Ta2O5 films are obtained, which are amorphous and extremely smooth. Their refractive index is in the range of 2.05–2.2, while the optical losses are below 3 dB/cm. Finally, in view of applications in biosensors experiments are presented to functionalize the surfaces of these films with amine and epoxy groups.

Tantalum pentoxide thin films have been deposited at room temperature by (dual) ion beam sputtering for applications as waveguides in biosensors. The oxygen partial pressure and the energy of the substrate ion beam were the major parameters varied in ion beam sputtering and dual ion beam sputtering experiments, respectively. For sufficiently high oxygen partial pressures, the films were stoichiometric, free of contaminants, amorphous, and extremely smooth. Ion bombardment of the growing films with Ar+ ions up to 200eV had no significant influence on these properties. The refractive index of stoichiometric films was 2.1±0.1 and the extinction coefficient well below the resolution limit of ellipsometry and UV/visible measurements. By coupling a laser beam via an optical grating into a 150nm thick Ta2O5 layer, the optical losses could be estimated to be below 3dB∕cm. A series of experiments has been carried out to prove that this deposition process is compatible with the use of thermoplast substrates which are sensitive not only to high temperatures but also to ion bombardment and UV radiation. Finally, first experiments are presented to functionalize the surfaces of Ta2O5 films with amine and epoxy groups.

A novel, non-disruptivebeam profile monitor for low in- tensity light-ion beams has been constructed and tested. The system is designed for use in medical hadrontherapy centers where real-time monitoring of the beam intensity profile is of great importance for optimization of the ac- celerator operation, patient safety and dose delivery. The beam monitor is based on the detection of secondary elec- trons emitted from a submicron thick Al2O3 foil placed in the beam at an angle of 45 degrees. The present paper re- ports the latest results achieved with a customized back- thinned monolithic active pixel array, which provides the beam intensity and position with a precision of better than 1 mm at a 10 kHz frame rate. The monitorperformancehas been tested with a patterned beam, produced with a multi- hole collimator, with the results indicating that the system performs according to its design specifications.

Superhard nanostructured coatings, prepared by plasma-assisted chemical vapour deposition (PACVD) and physical vapour deposition (PAPVD) techniques, such as vacuum arc evaporation and magnetron sputtering, are receiving increasing attention due to their potential applications for wear protection. In this study nanocomposite (TiAl)BxNy (0.09 <= x <= 1.35; 1.07 <= y <= 2.30) coatings, consisting of nanocrystalline (Ti,Al)N and amorphous BN, were deposited onto Si (100), AISI 316 stainless steel and AISI M2 tool steel substrates by co-evaporation of Ti and hot isostatically pressed (HIPped) Ti-Al-B-N material from a thermionically enhanced twin crucible electron-beam (EB) evaporation source in an Ar plasma at 450 degrees C. The coating stoichiometry, relative phase composition, nanostructure and mechanical properties were determined using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), in combination with nanoindentation measurements. Alummium (similar to 10 at.% in coatings) was found to substitute for titanium in the cubic TiN based structure. (Ti,Al)B0.14N1.12 and (Ti,Al)B0.45N1.37 Coatings with average (Ti,AI)N grain sizes of 5-6 nm and either similar to 70, or similar to 90, mol% (Ti,Al)N showed hardness and elastic modulus values of similar to 40 and similar to 340 GPa, respectively. (Ti,Al)B0.14N1.12 coatings retained their 'as-deposited' mechanical properties for more than 90 months at room temperature in air, comparing results gathered from eight different nanoindentation systems. During vacuum annealing, all coatings examined exhibited structural stability to temperatures in excess of 900 degrees C, and revealed a moderate, but significant, increase in hardness. For (Ti,Al)B0.14N1.12 coatings the hardness increased from similar to 40 to similar to 45 GPa. (c) 2006 Elsevier B.V All rights reserved.

TiAlB coatings with different compositions were deposited by co‐sputtering from TiAl and TiB 2 targets onto AISI316 stainless steel substrates at a temperature of 170 °C. The stoichiometry and nanostructure have been studied by X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Analysis of the XPS spectra suggests the presence of phases in agreement with the equilibrium TiAlB phase diagram. Diffraction studies (XRD and TEM) indicate that coatings with B/Al ratios <6 are amorphous, while coatings with B/Al ratios >6 exhibit a nanocomposite structure with average TiB 2 grain sizes of ∼2–3 nm for the highest B/Al ratio of 16. Nanocomposite coatings show significantly improved H/E ratios that are beneficial for protecting soft steels and light alloys. Copyright © 2006 John Wiley & Sons, Ltd.

Nanocomposite films consisting of diamond nanoparticles of 3-5 nm diameter embedded in an amorphous carbon matrix have been deposited by means of microwave plasma chemical vapour deposition (MWCVD) from CH4/N-2 gas mixtures. Si wafers, Si coated with TiN, polycrystalline diamond (PCD) and cubic boron nitride films, and Ti-6Al-4V alloy have been used as substrates. Some of the substrates have been pretreated ultrasonically with diamond powder in order to enhance the nucleation density n(nuc). It turned out that n(nuc) depends critically on the chemical nature of the substrate, its smoothness and the pretreatment applied. No differences to the nucleation behaviour of CVD PCD films were observed. On the other hand, the growth process seems to be not affected by the substrate material. The crystallinity (studied by X-ray diffraction) and the bonding environment (investigated by Raman spectroscopy) show no significant differences for the various substrates. The mechanical and tribological properties, finally, reflect again the influence of the substrate material: on TiN, a lower hardness was measured as compared to Si, PCD and c-BN, whereas the adhesion of c-BN/nanocrystalline diamond (NCD) system was determined by that of the c-BN film on the underlying Si substrate. (c) 2006 Elsevier B.V. All rights reserved.

Nanocrystalline diamond/amorphous carbon (NCD/a-C) composite films have been deposited by microwave plasma chemical vapour deposition from CH4/N2 mixtures. They consist of diamond nanocrystals of 3–5 nm grain size, embedded in an amorphous matrix with a thickness of 1–1.5 nm. The matrix is mainly sp3 bonded, with about 20–30% sp2 material, and contains 10% hydrogen in the form of sp3 CHx units. The influence of the substrate temperature on the growth and the properties of the films was investigated in the range from 520 to 770 °C. The growth rate increases with increasing temperature, indicating a thermally activated process. The apparent activation energy of 0.38±0.02 eV is lower than the values found for standard diamond deposition, thereby proving that differences between both processes exist. X-ray diffraction revealed that the crystalline properties of the NCD films (e.g. the grain size) are not affected by the temperature. From Raman and infrared measurements, it becomes evident, however, that the properties of the matrix are distinctively different at low and high temperatures, respectively. Possible reasons for these observations are discussed in some detail.