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Thin TiO 2 films were grown with a new solid titanium pyrazolylborate precursor by thermal metal organic chemical vapour deposition (MOCVD) in a temperature range of 300–800°C. Previous differential thermal analysis/thermogravimetric measurements have shown that this precursor is suitable for reduced pressure MOCVD systems. The amorphous character of the films deposited on quartz, sapphire, and Si [1 0 0] substrates was proven by X-ray diffraction. Oxygen and ammonia were used as reaction gases.

X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to study the influence of fluorine contamination on aluminium microchip bond pads. Sputter depth profiles indicated that the oxide layer thickness on those band pads, which showed poor gold wire adhesion, was higher than the thickness of the native oxide layer of aluminium. This corrosion was induced by segregation of fluorine into the bulk during storage of the wafers in closed polypropylene boxes. The contamination was found to be of the Al(OF)x type, which was initially formed in the CF4/O2 plasma-etching process. On test samples of aluminium metallization that have been stored with the process wafers, the fluorine contamination was located on the surface only. No segregation and no further oxidation occurred. In this case the fluorine contamination is of the AlFx type.

Intermetallic Ni 3 Al thin layers and Ni 3 Al/Ni multilayers were deposited on a Si wafer by means of magnetron sputtering. The structure and morphology of the layers have been characterized by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The polycrystalline films are textured in the (111) direction and have grain sizes below 20 nm. Superlattice reflections due to chemical order have been observed in the electron microscope. It is shown by x-ray diffraction that the multilayers grow coherently on the amorphous substrate.

Metal-on-metal (MoM) bearings are at the forefront in hip resurfacing arthroplasty. Because of their good wear characteristics and design flexibility, MoM bearings are gaining wider acceptance with market share reaching nearly 10% worldwide. However, concerns remain regarding potential detrimental effects of metal particulates and ion release. Growing evidence is emerging that the local cell response is related to the amount of debris generated by these bearing couples. Thus, an urgent clinical need exists to delineate the mechanisms of debris generation to further reduce wear and its adverse effects. In this study, we investigated the microstructural and chemical composition of the tribochemical reaction layers forming at the contacting surfaces of metallic bearings during sliding motion. Using X-ray photoelectron spectroscopy and transmission electron microscopy with coupled energy dispersive X-ray and electron energy loss spectroscopy, we found that the tribolayers are nanocrystalline in structure, and that they incorporate organic material stemming from the synovial fluid. This process, which has been termed "mechanical mixing," changes the bearing surface of the uppermost 50 to 200 nm from pure metallic to an organic composite material. It hinders direct metal contact (thus preventing adhesion) and limits wear. This novel finding of a mechanically mixed zone of nanocrystalline metal and organic constituents provides the basis for understanding particle release and may help in identifying new strategies to reduce MoM wear.

Various concentrations of chromium and titanium were codeposited on sapphire and WC/Co substrates in a high-purity nitrogen atmosphere at a pressure of 10−4 Torr. Diffraction studies and X-ray photoelectron spectroscopy revealed the formation of amorphous CrTioxynitrides. The deposits transformed to an extremely fine Cr+Ti(NO) cermet upon crystallization in a vacuum furnace at 800°C. Friction, wear and chemical resistance tests as well as electrical conductivity measurements were performed. It was found that the electrical conductivity and chemical resistance of the films simultaneously increased with Cr concentration while both low friction and low wear were retained.

In situ information on nanoparticle surface chemistry and modes of particle growth is obtained in gas suspension by the technique of photoelectric charging of particles (PCP) which depends on the surface chemical compositon as well as the electronic structure of the particles via the spectral dependence of the photoelectric yield. With CuCl particles, photoelectric charging is about 100 times more efficient compared to other divalent transition metal compounds. Therefore, particles containing monovalent Cu can be detected with extremely high sensitivity of below 10 ng/m3. In atmospheric aerosols emitted from volcanoes, the relation of solid state oxidation/reduction in Fe1−xCuxCl2 resulting in monovalent Cu for x

A quantitative method using Rockwell C indentation was developed to study the adhesion of diamond-like carbon (DLC) protective coatings to the CoCrMo biomedical implant alloy when immersed in phosphate-buffered saline (PBS) solution at 37 degrees C. Two kinds of coatings with thicknesses ranging from 0.5 up to 16 microns were investigated, namely DLC and DLC/Si-DLC, where Si-DLC denotes a 90 nm thick DLC interlayer containing Si. The time-dependent delamination of the coating around the indentation was quantified by means of optical investigations of the advancing crack front and calculations of the induced stress using the finite element method (FEM). The cause of delamination for both types of coatings was revealed to be stress-corrosion cracking (SCC) of the interface material. For the DLC coating a typical SCC behavior was observed, including a threshold region (60J m(-2)) and a "stage 1" crack propagation with a crack-growth exponent of 3.0, comparable to that found for ductile metals. The DLC/Si-DLC coating exhibits an SCC process with a crack-growth exponent of 3.3 and a threshold region at 470 Jm(-2), indicating an adhesion in PBS at 37 degrees C that is about eight times better than that of the DLC coating. The SCC curves were fitted to the reaction controlled model typically used to explain the crack propagation in bulk soda lime glass. As this model falls short of accurately describing all the SCC curves, limitations of its application to the interface between a brittle coating and a ductile substrate are discussed.

Scanning Auger microscopy investigations were carried out to solve many problems in research and applications from customers in Swiss industry. Using this high lateral resolution technique (less than 100 nm), with a surface sensitivity in the nanometer range, it is possible to analyze small contaminations, inclusions, odd elements etc. Using small spot electron spectroscopy for chemical analysis in addition, further information on the chemical states (valence) of the elements involved can be obtained.

a-C:H (amorphous carbon) superhard coatings have a wide range of applications due to their unique properties. SAM (scanning Auger microscope) depth profiles have been measured for a-C:H films on several substrates in order to obtain information on the a-C:H/substrate interface which is governing the adhesion properties of these coatings. To extract the chemical information from the Auger depth profile analysis through an a-C:H thin film on Si(111) a TFA (target factor analysis) followed by a target transformation to the Si, C, SiC single component spectra was performed. This analysis provides chemically resolved Auger depth profiles and the number of chemical compounds that contribute to the spectra as well as the thickness of the interlayer. The interlayer between the film and the substrate could be resolved both stoichiometrically and chemically, although it was only a few nanometers thick.

Auger electron spectroscopy (AES), x‐ray photoelectron spectroscopy (XPS), and electron microprobe analysis (EMA) were applied to investigate the chemical composition, impurities, and the homogeneity of thin para‐ and ferroelectric epitaxial KTa1−xNbxO3 (KTN) layers grown by liquid‐phase epitaxy using a KTN‐KF flux. AES indicated no Ta/Nb fluctuations within the layer plane and in the growth direction. XPS and EMA determined a F incorporation of 0.8–0.9 mol % for as‐grown and 0.6 mol % for annealed samples. Valence analyses with XPS and electron paramagnetic resonance (EPR) revealed only the regular valence state for the B atoms of a (I,V)ABO3 perovskite lattice. An unexpected splitting of the K 2p doublet peak was found for as‐grown layers. Structural defects observed by optical microscopy and x‐ray topography were attributed to lattice relaxation effects. Optical waveguiding could be achieved for para‐ and ferroelectric layers.

Boronisation of the TCA vacuum vessel was performed at ambient temperature. The paper presents detailed surface analysis of the coating and a description of the tokamak performance after boronisation. The obtained coatings showed a film composition close to the feed gas composition although a high oxygen content was measured. Apart from the dominating carbidic B-C bonds, the existence of at least two non-equivalent carbon bonding sites were found. Boronisation gave an immediate and long-term improvement of many plasma parameters in TCA with a strong reduction of both low and high-Z impurities in the plasma. In particular oxygen was reduced by over 20 despite a high level oxygen contamination in the coating. The gas retention in the film has been shown to be temporarily reduced by glow discharge cleaning. With these techniques we are able to obtain nearly isotopically pure discharges. Boronisation has been shown to be a very efficient wall conditioning procedure in TCA.

For nonmagnetic disordered metals Nagel and Tauc have proposed an electronic influence on stability due to an electron-mediated indirect interaction between the ions. This interaction causes a structure-induced minimum in the electronic density of states and electronic-induced structure properties. In the present paper we show indications for another influence, electron-mediated as well, due to indirect magnetic interaction between local moments. Interrelations between electronic and structural properties and their influence on stability and magnetic properties are shown for FexX1−x metallic glasses (X: Sn, Ge, Sb).

Bimetallic Pd-Au and Pt-Au and monometallic Pd, Pt, and Au films were prepared by physical vapor deposition. The resulting surfaces were characterized by means of XPS, AFM, and CO adsorption from the liquid phase (CH2Cl2) monitored by ATR-IR spectroscopy. CO adsorption combined with ATR-IR proved to be a very sensitive method for probing the degree of interdiffusion occurring at the interfaces whose properties were altered by variation of the Pd and Pt film thickness from 0.2 to 2 nm. Because no CO adsorption was observed on Au, the evaporation of Pt-group metals on Au allowed us to study the effect of dilution on the adsorption properties of the surfaces. At equivalent Pd film thickness, the evaporation of Au reduced the amount of adsorbed CO and caused the formation of 2-fold bridging CO, which was almost absent in monometallic surfaces. Additionally, the average particle size on Pd-Au surfaces was smaller than that on monometallic Pd surfaces. The results indicate that a Pd/Au diffuse interface is formed that affects the Pd particle size even more drastically than the simple decrease in Pd film thickness in monometallic surfaces. Pt-Au surfaces were less sensitive to CO adsorption, indicating that the two metals do not mix to a significant extent. The difference in the interfacial behavior of Pd and Pt in the bimetallic gold films is traced to the largely different Pd-Au and Pt-Au miscibility gaps.

Amorphous hydrogenated carbon (a-C:H) films have many outstanding properties required for a protective coating material on load bearing medical implants. Recently, titanium doped a-C:H films have been evaluated regarding their effects on bone marrow cell cultures. But many materials that are well-tolerated in bulk form are able to induce toxic reaction if present particulate form. In order to further assess biocompatibility aspects of these two coatings, film delamination has been mimicked in exposure to fluids. In the present study, particles from a-C:H, a-C:H/Ti and a-C:H-a-C:H/Ti bilayer films were added to bone marrow cell cultures in vitro. The results showed that plain a-C:H and to a certain extent a-CH/Ti particles were inert. Both kinds of particles did not significantly stimulate the osteoclast-related enzyme tartrate resistant acid phosphatase (TRAP). A slight increase in cell proliferation and total culture TRAP was found in cultures treated by a-C:H-a-C:H/Ti bilayer films. Latter effect can probably be traced back by the relative high percentage of small particles of a size of around 2 microm. However, if corrected by the cell number also no differences between particle-treated and untreated control cultures could be found, indicating the absence of a toxic effect from delaminated a-C:H coatings.

Hard amorphous hydrogenated carbon, also referred to as diamond-like carbon films, are of technological interest as protection coatings due to their special properties such as high hardness, low friction, low wear, chemical inertness and electrical insulation. In this paper a study of the adhesion properties of multilayer structures composed of DLC/Metal/DLC/substrate is presented. As substrates a ball and roller bearing steel (DIN 1.3505, AISI 52100) was used. After Ar plasma cleaning of the substrate, DLC films were deposited from acetylene gas by rf plasma chemical vapor deposition at a self-bias of -600V. Metal films were deposited in the same chamber by DC magnetron sputtering.Adhesion of the different layers on the underlying layer was investigated by optical analysis of the coating at the border of Rockwell C indentations made into the substrate. If necessary, additional thin layers are deposited at the particular interface to ensure good adhesion. Further information on the interface quality and hence the adhesion is gained by a second optical analysis of the Rockwell indentation after exposure to ambient air for two weeks.The multilayer structure containing titanium as the metal layer showed no ablation of the coating around the indentation even after two weeks of exposure to ambient air. Chromium on the other hand already showed some ablation immediately after the indentation as well as still ongoing ablation after two weeks. These results are further corroborated by pin-on-disc tests.

Amorphous hydrogenated carbon (a-C:H) exhibits outstanding properties such as high hardness, low mechanical wear and friction, high thermal conductivity, etc. These properties are irreversibly altered above 400 °C. Doping the a-C:H films with nitrogen revealed the possibility to continuously tune properties such as internal stress, hardness, electrical conductivity and surface energy. X-ray photoelectron spectroscopy has been used to analyze the chemical and structural modifications caused by the introduction of nitrogen into the films. An increased onset temperature of the thermal C-H bond decomposition in a-C:H films up to 600 °C (in vacuum) is observed. Hardness measurements on N-doped samples show an increase in thermal stability of the films, however, without ever reaching the hardness values obtained from the undoped a-C:H film.

Three efficient and straightforward chemical pathways have been studied to functionalize solid cellulose substrates, involving for the first time alkoxysilane chemistry coupled with the photochemical version of the thiol-ene reaction. The success of the reactions was confirmed using FTIR-ATR spectroscopy and XPS analysis, but different grafting efficiencies were observed depending on the combination used. In a first route, ene-functionalized cellulose films were synthesized using vinyltrimethoxysilane as coupling agent, and were photochemically coupled with methylthioglycolate (MeGlySH). A very fast reaction rate was observed for this reaction during the first 5 min. In a second route, the opposite reaction was envisaged by clicking allylbutyrate on a thiol-functionalized cellulose surface, previously synthesized using 3-mercaptopryltrimethoxysilane as coupling agent. The success of the reaction was highlighted, but lower modification rates were observed. In a third route, a novel approach was successfully proposed for the grafting of thiol molecules on cellulose, based on the click derivatization of the molecule with alkoxysilane functions. Through this study, we expand the modular and versatile character of click chemistry to natural cellulosic substrates. But most importantly, these modification routes can be envisaged for the functionalization of other surfaces (i.e., metal alkoxides for instance) where alkoxysilane chemistry can be employed.

The copper precursors bis-hexafluoroacetylacetonato-copper Cu ~hfac) 2 , vinyl-trimethyl-silane-copper~I!-hexafluoroacetylacetonate ~hfac!Cu~VTMS!, 2-methyl-1-hexen-3-yne-copper-hexafluoroacetylacetonate ~hfac!Cu~MHY!, and dimethylbutene-copper~I!-hexafluoroacetylacetonate ~hfac!Cu~DMB! are compared with respect to deposition rates and metal content obtained by focused electron beam induced deposition. Exposure was performed with 25 keV electrons in a Cambridge S100 scanning electron microscope equipped with a lithography system. Tip deposition rates increase with increasing precursor vapor pressure and range between 47 nm/s for ~hfac!Cu~DMB! to about 4 nm/s for Cu~hfac) 2 . A decay of deposition rates with time, i.e., tip length, is observed. Electric 4-point measurements indicate an insulating behavior of deposited lines for all precursors. In contrast, Cu contents of up to 45-60 atom % were found by Auger electron spectroscopy in thin rectangular deposits using ~hfac!Cu~DMB! and ~hfac!Cu~VTMS! as precursors. A discussion in terms of monolayer coverage, completeness of precursor molecule dissociation, and precursor stability is presented.

Low-cost linear arrays of deflectable micromirrors using a CMOS-compatible process to define both on-chip circuitry and the mirror structure are presented. The mirrors consist of the CMOS second metal layer deposited in two successive passes in order to establish a thick metal layer for the stiff mirror plate as well as a thin one for the flexible hinges. The mirrors are released by sacrificial aluminum and oxide etching. Supercritical point drying is performed in order to avoid sticking of the mirrors to the substrate. The mirrors are electrostatically deflected by biasing the address electrodes implanted into the substrate underneath the mirror plate. Full angular deflection by ± 4.8 deg of a 30 3 40-µm2 plate is achieved with a driving voltage of 11 V. On-chip circuitry adjacent to each mirror allows one to address the pixels with 5-V data pulses. The reflectance of the aluminum surface for wavelengths between 400 and 700 nm was measured to be 83% to 89%. The mirror surface was further characterized using Auger spectroscopy, showing that no optically relevant surface modifications occur during postprocessing. The surface rms roughness measured by atomic force microscopy is on the order of 25 nm.

We present a photoemission study of the CO adsorption on amorphous Ni-Zr alloys at various compositions. Our results indicate a distinct enhancement of dissociative adsorption even at very low Zr concentrations. These observations are supported by LCAO-type calculations of potential energy surfaces, which suggest a strong increase of backdonation into antibonding CO 2π∗ type orbitals near Zr sites.

57Fe Mossbauer and photoemission measurements were performed on meltquenched amorphous Fe(Zr, B) and (Fe, Ni)B alloys. The atomic and electronic structure of Fe90Zr10 and Fe88B12 glasses were found to be different. Half of the Zr content could be replaced by B in the Fe90Zr10 glass without changing its structure. Mossbauer investigation of the amorphous (Fe1−xNix)100−yBy (0

Volcanic gases contain ultrafine aerosol particles in the nanometer size range; typical concentrations are 105 to 106 cm−3. Photoelectric charging of particles (PCP) is an in situ method for the material specific detection of very small particles in a gas. Field studies at degassing lava flows of Mount Etna, Sicily, and Kilauea, Hawaii, show that the chemistry of the ultrafine aerosols depends strongly on the degassing state of the lava. Heating of a relatively undegassed lava sample in the laboratory reveals the chemical nature of the particles that form by nucleation and condensation in the cooling gas. In the initial stages of degassing, the particles are mainly NaCl and KCl nanocrystals that contain iron oxide and copper chloride. Cu is in the monovalent state, which is stable even in an oxidizing environment due to a redox mechanism with the Fe ions. The fraction of Cu(I) in the aerosols is determined by PCP. The evolution of the Cu(I) fraction is considered an effective tracer of chlorides in the magmatic gases and thereby of magma degassing. The PCP technique allows a fingerprint to be obtained of the magmatic gas by an aerosol measurement in the diluted plume.

Amorphous hydrogenated carbon films containing different amounts of fluorine and silicon have been deposited by plasma activated chemical vapor deposition in a stainless steel high vacuum system, using different mixtures of acetylene and either trifluoromethane or tetramethylsilane. Film composition and the different chemical states present have been characterized by X-ray photoelectron spectroscopy. Cell culture tests with fibroblasts revealed a good surface biocompatibility by means of morphological behavior, but no dependence on the Si or F content in the a-C:H films could be seen. All cells showed good spreading on the surface. Within 2 days confluent cell layers were observed.

Amorphous hydrogenated carbon films are of technological interest as protection coatings due to their special properties such as high hardness, chemical inertness, electrical insulation and infrared transparency. However, some applications still suffer from the poor thermal stability and adhesion problems of these coatings. To ensure good adhesion, especially on hardened steels and non-carbide forming substrates, an extra interlayer has to be deposited first. Often a silicon containing interlayer, Si-a-C:H for example, is used for this purpose. This Si-a-C:H interface layer was deposited by rf plasma deposition from tetramethylsilane. Then a-C:H films containing Si-O with a varying silicon content were produced from a mixture of acetylene and hexamethyldisiloxane. The structural changes upon annealing of these films were investigated using Raman spectroscopy. The analysis of the development of the different peaks upon annealing temperature reveals the transition from the amorphous structure to the more graphitic-like structure. This transition temperature increases by as much as 100°C when silicon is incorporated into the DLC film. However, when Si-O is incorporated instead of only silicon the same increase in temperature stability is observed.

In the present interlaboratory comparison, the consistency and validity of the Shirley, straight-line and Tougaard methods for determination of peak intensities from measured XPS spectra have been studied by analysis of data on Au and Ni taken at eight laboratories. The reproducibility of the individual measuring systems was determined to be 2–6%. The RMS scatter around their mean values of the ratio of the peak intensity to the Au 4d peak intensity was 6% for the Tougaard method, 9–10% for the Shirley method and 8–9% for the straight-line method. The increase in root mean square (RMS) scatter of data due to data being recorded in different laboratories amounts to 3–4%, independent of the method applied for background correction. The RMS deviation from theory of intensity ratios of peaks from Ni and Au to the Au 4d peak intensity is 14% for the Tougaard method, 33% for the Shirley method and 31% for the straight-line method. The absolute accuracy of the methods cannot be established to better than the accuracy on the theoretical peak intensity ratios and the uncertainty in the energy dependence of the analyser response function. It is, however, reasonable to expect the combined uncertainty of these factors to be at least 10–15%. The peak intensity ratios obtained with the Tougaard method then falls within the expected accuracy of the theoretical ratios.

The structural, electronic, and dielectric properties of barrier -type anodic Al oxides prepared with various thicknesses have been investigated. The planar and cross morphologies as well as the surface charge distribution were investigated as a function of the voltage applied during growth, i.e. the thickness. Three distinct anodizing potential domains can be clearly identified. A transition in ionic mobilities induces, at anodizing voltage higher than 100 V, the built-up of space charge region in the anodic films. A correlated increased oxide density with growing anodization potential is consistently pointed out by Volta Potential Difference and XPS/Auger measurements. The full dielectric response of the oxides, including both the lattice and electronic components, has been accessed by electrochemical impedance spectroscopy and Auger analysis. The lattice contribution of the dielectric constant is found to be strongly affected by the growth voltage, as a clear increase in the lattice component of the dielectric constant is observed, reaching values close to those of bulk crystalline Al2O3 structures. At variance, the electronic contribution is only slightly affected. The results have been compared to dielectric constants calculated for atomistic amorphous models within the framework of density functional theory. It is shown that amorphous Al2O3 models of higher density lead to dielectric constants that could explain the trend observed in theseries of barrier-type anodic oxides prepared in this work. (C) 2016 Elsevier Ltd. All rights reserved.

The interface between diamond-like amorphous hydrogenated carbon (a-C : H) and Al2O3 was analysed by sputter depth profile analysis via x-ray photoelectron spectroscopy. X-ray photoelectron spectra were also recorded during direct ion beam deposition (CH4, E = 400 eV) monitoring the initial build-up of the interface. No stoichiometric interface compound was detected, although Al2O3 is reduced to Al2O3-x (x ∼ 0.5–1) enabling an interaction with the carbon atoms. This results in an excellent adhesion of a-C : H to the chemically inert Al2O3.

The original state of the interface between ultrahard amorphous hydrogenated carbon (a-C : H) and aluminum was analyzed by non-destructive in-situ direct ion beam deposition (CH 4 , −400 V) as well as angle resolved XPS (X-ray photoelectron spectroscopy) analysis through a thin a-C : H coating. Depending on the deposition conditions a 0.6 to 1.9 nm thick Al 4 C 3 interlayer, held responsible for the good adhesion between a-C : H and Al, could clearly be resolved. Furthermore, an interaction between a-C:H and Al 4 C 3 at the a-C : H/Al 4 C 3 interface was detected. The ability of C and Al to form a reactive Al 4 C 3 interface as well as an interaction of a-C : H with Al 4 C 3 has also been confirmed by XPS and AES sputter depth profile analysis.

The near normal incidence reflectivity of the ferromagnets U 3 P 4 and U 3 As 4 and the isostructural but diamagnetic compounds Th 3 P 4 and Th 3 As 4 has been measured from 0.03 to 12 eV. Trithorium tetraphosphide and tetraarsenide are shown to be indirect gap semiconductors with gap energies of 0.43 and 0.39 eV, respectively. U 3 P 4 and U 3 As 4 display similar sets of p→d transitions than the corresponding thorium compounds, however, they are shifted by 0.85 eV to lower photon energies. It is concluded that the uranium compounds are metals due to a merging of the valence p band into the 6d conduction band giving direct experimental evidence for a p-f mixing effect of the same size. Energy level schemes are derived.

Silicon (Si) based implantable components are widely used to restore functionalities in the human body. However, there have been reported instances of Si corroding after only a few years of implantation. A key parameter often overlooked when assessing Si stability in-vitro, is the added constricting geometries introduced through in-vivo implantation. The influence of crevices and confined solutions on the stability of Si is presented in this study, considering two simulated physiological solutions: 0.01 M phosphate buffered saline (PBS) and HyClone Wear Test Fluid (WTF). It was found that Si is highly vulnerable to corrosion in confined/crevice conditions. High pitting corrosion susceptibility is found in a crevice, whereas a dissolution rate of ca. 3.6 nm/h at body temperature occurred due to local alkalization within a confined cathodic area. The corrosion rates could be increased by elevating the temperature and yielded linear Arrhenius relations, with activation energies of 106 KJ/mol in 0.01MPBS and 109 KJ/mol in HyClone WTF, corresponding to a phosphorous-silicon interaction mechanism. Phosphorous species favored corrosion and contributed to enhanced Si dissolution, while chlorides were not so influential, and applied anodic potential induced pseudo-passivation. These results highlight the importance geometrical configurations can have on a material's surface stability. (c) The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

The hardness of hydrogenated amorphous carbon (a-C:H) films is difficult to sustain at application temperatures above 400 °C. In this study, using Raman spectroscopy we examined the structural behaviour of Mo, Cu or N doped a-C:H films annealed at various temperatures up to 800 °C. The intensity of the Raman disorder peak (D-peak) of graphite increased with increasing annealing temperature regardless of the type of dopant. In the case of pure a-C:H, the as-deposited film was mainly formed of random-network-type (RN-type) planar clusters along with very small turbostratic-carbon-type (TC-type) clusters. When annealed, the RN-type clusters transformed gradually into very small TC-type clusters while already existing TC-type clusters grew to larger sizes. When 0.6 at.% Mo was integrated into a-C:H in a multilayer fashion, a very small amount of TC-type clusters formed in as-deposited films. When annealed, Mo in the multilayer structure was found to be beneficial for retaining smaller TC-type clusters. Mo and Cu, when incorporated by a codeposition method, lowered the temperature of formation of relatively larger TC-type clusters, similar to the effect of nitrogen.