Two PVD titanium nitride based coatings; monolayer TiN and multilayer resulting from the stacking of TiN and (Ti,Al)N layers were evaluated with respect to their stress state and microstructure. The TiN was deposited by triode evaporation ion plating, whereas the TiNy(Ti,Al)N was deposited using a reactive hybrid deposition process consisting of a combination of electron beam evaporation of Ti and DC magnetron sputtering of a Ti-Al alloy. The structural and mechanical state characterisations of the as-deposited coatings on steel substrates were performed using X-ray diffraction methods. The Bragg-Brentano geometry was used to study the texture and the sin c method was applied to obtain the stress-free lattice parameter, the Poisson's ratio 2 and the residual stresses. The monolayer exhibited a preferred orientation with (1 1 1) parallel to the surface. However, the TiN and (Ti,Al)N layers from the multilayer revealed a slightly (3 1 1) preferred orientation. All coatings were in a state of compressive stress ranging from 10.1 to 2.7 GPa, depending logically on the substrate material, layer thickness and deposition processes. The microstructure and composition of the coatings were investigated using a combination of scanning electron microscopy, plan-view and cross-sectional transmission electron microscopy, energy-dispersive spectroscopy and electron energyloss spectroscopy. The TiN exhibited a fibrous microstructure where only a few columns extended through the whole coating thickness. The TiNy(Ti,Al)N multilayer revealed a more pronounced columnar microstructure with the columns extending throughout the film thickness. Micrometer-sized macroparticles were present in the multilayer at various distances from the substrate, but never at the substrate surface. The results showed that they were incorporated in the growing film in the solid state and consisted of a core structure with equiaxed grains having the a-Ti phase and an outer layer of TiN. Evidence was found of nitrogen diffusion, presumably from both the working gas into the solidifying Ti droplet during migration to the film and through the TiN outer layer. ᮊ
Tungsten oxide coatings were deposited without substrate bias by DC reactive magnetron sputtering of a tungsten target using oxygen as reactive gas. By tuning the partial pressure of oxygen ( p O 2 /p Ar ) between 0 and 4, the oxygen content of the films was changed from 0 to 75 at.%. The structure of the films (investigated by X-ray diffraction) depends on their oxygen content. For low oxygen contents, the a-W and h-W 3 O phases were observed (< 30 at.%), and with the increase of oxygen content (30 at.% < O < 67 at.%) the structure became amorphous. A transition region was obtained for oxygen content between 67 at.% and 75 at.%, and when O > 75 at.%, a nanocrystalline (WO 3 ) structure was reached.The hardness and Young's modulus were evaluated by depth sensing indentation. The decrease in hardness followed the four different ranges of chemical compositions accordingly, from å 23 GPa for pure W down to å 7 GPa for WO 3 films. A similar behaviour was observed for the Young's modulus, which ranged from 450 GPa to 150 GPa. The cohesion/adhesion of the films were investigated using a scratch-test apparatus. These coatings displayed a low adhesion (critical load, L c < 15 N) to the steel substrate because the depositions were carried out intentionally without an adhesion interfacial layer. D
The focus of this research is the X-ray photoelectron spectroscopy (XPS) analysis of thin films consisting of Au metal clusters embedded in a dielectric matrix of Al-O coatings. The coatings were deposited by co-sputtering an Al+Au target in a reactive atmosphere with Au contents up to 8 at.%. The Al-O matrix was kept amorphous even after annealing at 1000°C. In the as-deposited films the presence of Au clusters with sizes smaller than 1-2 nm (not detected by XRD) was demonstrated by XPS. With increasing annealing temperature, Au clustering in the dielectric matrix was also confirmed by XPS, in agreement with XRD results.
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