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

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Geometric-shape-dependent structural transition behavior in (110) SrRuO3 epitaxial thin films Structure and strain relaxation mechanisms of ultrathin epitaxial Pr 2 O 3 films on Si(111) J. Appl. Phys. 97, 074906 (2005); 10.1063/1.1883304Switchable yttrium-hydride mirrors grown on CaF 2 (111): A x-ray photoelectron spectroscopy and diffraction studyThe detailed mechanisms of the structural phase transformations that occur in epitaxial Y-hydride switchable mirrors are revealed with high resolution transmission electron microscopy ͑both cross sectional and plan view͒. The triangular ridge network that develops in Y prior to the ␣-␤ transformation is a result of ͕101 2͖ deformation twinning. The basal plane that is originally parallel to the film/substrate interface is rotated by twinning over 5.6°and transformed into a prismatic plane and similarly the prismatic plane is transformed into a basal plane giving a final crystal reorientation for the ridge of 95.6°. After transformation to ␤, nearly vertical ⌺3͕111͖ twin boundaries arise in the ridges. In contrast, horizontal twin boundaries develop in the ␤ domains to prevent macroscopic shape changes. Inbetween the two twin variants within the domains, Shockley partial dislocations are persistently present, which enable efficient reversible ␤-␥ switching of the mirror.

A multilayer system consisting of TiN and TiAlN layers is deposited by means of a PVD process onto stainless and tool steel substrates. The study is aimed at determining the microstructure and the macrostresses in these layers with X-ray diffraction. The multilayer system is composed of a relative thick TiAlN layer (∼150 nm) and a set of smaller alternating TiN/TiAlN layers of approximately 15–20 nm each with a total thickness of 150 nm. This basic building block of the structure is repeated throughout the coating and is sandwiched between two thicker layers: a TiN layer (400 nm) to achieve good adhesion with the substrate, and a top layer of TiAlN (400 nm). The total thickness of the coating is approximately 4·4 μm. From X-ray diffraction it is concluded that the layers are only slightly textured and there is a weak (311) texture. The strain measurements show a difference in strain for the layers on stainless and tool steels, which is owing to a difference in the linear expansion coefficient for the two substrates. It is possible to determine the unstrained lattice spacing of the TiN and the TiAlN sublayers and to calculate Poisson's ratio for both materials. Furthermore, the residual stresses in the different sublayers could be derived and it was found that they were much higher in the TiN than in the TiAlN. This may be explained by the thermal origin of the residual stress in the TiAlN sublayers, whereas in the TiN sublayers the atomic peening process during deposition introduces an additional residual stress.