To clarify the underlying mechanisms that cause the preferred orientation in TiN films, we investigated the evolution with the thickness of the texture, surface morphology, and residual stress in TiN thin films deposited by dual ion beam sputtering. The films, with thickness h ranging from 50to300nm, were grown on oxidized Si substrates using a primary Ar ion beam accelerated under 1.2kV and different voltages Va of the (Ar+N2) assistance beam: 25, 50, and 150V. The influence of temperature was also investigated by varying the substrate temperature Ts (25–300°C) during growth or by performing a postdeposition annealing. X-ray diffraction (XRD) as well as transmission electron microscopy were used to study the microstructure and changes of texture with thickness h, while x-ray reflectivity and atomic force microscopy measurements were performed to determine the surface roughness. Residual stresses were measured by XRD and analyzed using a triaxial stress model. The crystallite group method was used for a strain determination of crystallites having different fiber axis directions, i.e., when a mixed texture exists. The surface roughness is found to increase with Va and Ts due to the resputtering effect of the film surface. XRD reveals that for a small thickness (h∼50nm) the TiN films exhibit a strong (002) texture independent of Va. For a larger thickness (100<h<300nm), the development of a (111) preferred orientation is observed together with a grain size increase, except at Ts=300°C, where the predominant texture remains (002). A minor (220) texture is also found, but its contribution strongly decreases with Va and Ts. The residual stresses are highly compressive, ranging from −8to−5GPa, depending on the deposition conditions. When a mixed texture exists, the analysis reveals that (111)-oriented grains sustain stresses that are about 20% more compressive than those sustained by (002)-oriented grains. The present results suggest that the change in the preferred orientation from (002) to (111) is not correlated with a strain energy minimization or with a systematic increase in surface morphology. Rather, kinetically driven mechanisms occurring during growth and linked to anisotropies in surface diffusivities, adatom mobilities, and collisional cascades effects are likely to control the texture development in TiN thin films produced with energetic ionic species. This interpretation is supported by in situ temperature XRD measurements.

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The effect of thermal cycling on transformation temperature was studied on a Ti-rich NiTi alloy. The study was carried out by determining the electrical resistance, the internal friction, and the elastic modulus vs temperature. This study shows that the martensite microstructure is modified by the successive cycling transformation. In addition, we established that both the martensite internal friction and the transition peak are sensitive to the transient effect (the vibration frequency lies around 300 Hz). But the major results concern the behavior associated with the R phase occurrence and its evolution. We have stated that the premartensitic phase becomes stable following the diminishment of the beginning of the martensite formation (M s ). Interrupted cooling has also shown that, contrary to the martensite, the R phase exhibits no hysteretic behavior.

In an effort to address the understanding of the origin of growth stress in thin films deposited under very energetic conditions, the authors investigated the stress state and microstructure of Mo thin films grown by ion beam sputtering (IBS) as well as the stress relaxation processes taking place during subsequent thermal annealing or ion irradiation. Different sets of samples were grown by varying the IBS deposition parameters, namely, the energy E0 and the flux j of the primary ion beam, the target-to-sputtering gas mass ratio M1∕M2 as well as film thickness. The strain-stress state was determined by x-ray diffraction using the sin2ψ method and data analyzed using an original stress model which enabled them to correlate information at macroscopic (in terms of stress) and microscopic (in terms of defect concentration) levels. Results indicate that these refractory metallic thin films are characterized by a high compressive growth stress (−2.6to−3.8GPa), resulting from the creation of a large concentration (up to ∼1.4%) of point or cluster defects, due to the atomic peening mechanism. The M1∕M2 mass ratio enables tuning efficiently the mean deposited energy of the condensing atoms; thus, it appears to be the more relevant deposition parameter that allows modifying both the microstructure and the stress level in a significant way. The growth stress comes out to be highly unstable. It can be easily relaxed either by postgrowth thermal annealing or ion irradiation in the hundred keV range at very low dose [<0.1dpa (displacement per atom)]. It is shown that thermal annealing induces deleterious effects such as oxidation of the film surface, decrease of the film density, and in some cases adhesion loss at the film/substrate interface, while ion irradiation allows controlling the stress level without generating any macroscopic damage.