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This work is focused on the transformation of the disordered fluorite cubic-F phase to the ordered cubic-C bixbyite phase, induced by isothermal annealing as a function of the residual stresses resulting from different concentrations of microstructural defects in the yttrium oxide, Y 2 O 3 . This transformation was studied using in-situ X-ray diffraction and was modelled using Kolmogorov–Johnson–Mehl–Avrami (KJMA) analysis. The degree of the disorder of the oxygen network was associated with the residual stress, which was a key parameter for the stability and the kinetics of the transition of the different phases that were present in the thin oxide film. When the degree of disorder/residual stress level is high, this transition, which occurs at a rather low temperature (300 °C), is interpreted as a transformation of phases that occurs by a complete recrystallization via the nucleation and growth of a new cubic-C structure. Using the KJMA model, we determined the activation energy of the transformation process, which indicates that this transition occurs via a one-dimensional diffusion process. Thus, we present the analysis and modelling of the stress state. When the disorder/residual stress level was low, a transition to the quasi-perfect ordered cubic-C structure of the yttrium oxide appeared at a rather high temperature (800 °C), which is interpreted as a classic recovery mechanism of the cubic-C structure. [ABSTRACT FROM AUTHOR]

Abstract: This work studies the ion irradiation-induced phase transformations in thin films of yttrium oxide. The films were deposited using an ion beam sputtering technique that allows the control of the order/disorder of the microstructure. As-deposited (disordered) and annealed (ordered) samples were irradiated by xenon ions at different energies and doses. Two different structural phase transformations were observed: cubic/amorphous-like and cubic/monoclinic. In both cases, it is shown that the pristine structure is of prime importance in the transformation process. The phase transformations are analysed in terms of structural extended defect nucleation originating from the oxygen network behaviour, which leads to polygonisation up to a nanocrystallite-like structure, followed by a phase transformation into a monoclinic structure. [Copyright &y& Elsevier]

Abstract: Y2O3 thin films are deposited by ion beam sputtering on Si, SrTiO3 and MgO substrates. In order to obtain a better knowledge on the phase transition mechanisms in yttrium oxide, the effects of ion implantation have been studied as a function of the initial microstructure of thin films. The different microstructures for the as-deposited and implanted samples have been studied and characterized by means of X ray diffraction, High Resolution Transmission Electron Microscopy and Electron Energy Loss Spectroscopy and are compared to the cubic-C and monoclinic-B phase of Y2O3. The experimental results show clearly the presence of non-equilibrium phases in the implanted and non-implanted thin films. A particular attention is paid to the understanding of the relationship between the oxygen vacancy network organization, the stoichiometry and the formation mechanisms of these crystallographic phases. [Copyright &y& Elsevier]

Thin films of yttrium oxide, Y2O3, were deposited on Si (1 0 0), MgO and SrTiO3 substrates by ion beam sputtering. The as-deposited samples are under a strong compressive stress whatever the substrates are. Furthermore the in-plane (2 2 2) or (4 0 0) Bragg peaks are shifted and non-symmetric. The high-resolution transmission electron microscopy investigations on the epitaxially grown Y2O3 thin films lead to the conclusion that the ion beam deposition process promotes a strong disorder on the oxygen network. The crystallographic symmetry of the Y2O3 structure which is Th7 becomes a fluorite related symmetry which is Fm3m. Annealing treatments or deposition involving a secondary ion beam assisted deposition process re-orders the Fm3m structure which comes back to the equilibrium Th7 symmetry. [Copyright &y& Elsevier]

Yttrium oxide thin films were in-situ deposited by ion beam sputtering on Si, MgO and SrTiO3 substrates. These Y2O3 thin films were investigated mainly by means of x-ray diffraction. The strained state of the oxide layers was studied by the sin2ψ method as a function of the deposition parameters as well as the post annealing treatments. An in situ study of the kinetics of the internal strain relaxation process was performed as a function of temperature. The Arhenius plot of relaxation rate gives the activation energy of this strain relaxation process, which is 1.3 eV. The results obtained in this work were interpreted in terms of crystal chemistry and the stoichiometry-microstructure relationship. [Copyright &y& Elsevier]

Worm-like buckling structures have been investigated by atomic force microscopy to estimate the relevant parameters for the mechanical stability of Y[SUB2]O[SUB3] thin films deposited by ion beam sputtering technique on GaAs substrates. The internal stresses involving in the observed buckling phenomena have been estimated to be around 8.5 GPa in compression. The critical thicknesses up to which the various damaging mechanisms occur have also been determined. [ABSTRACT FROM AUTHOR]

According to Cr content, ternary Al1-xCrxNy films structure evolves from hexagonal to cubic phase. Despite numerous studies on their mechanical properties in relation with the deposition process, the relationship between this phase transition and elastic properties has never been deeply studied. In this paper, the transition has been evidenced by picoseconds ultrasonic and Brillouin light scattering at a chromium concentration of 40 at. % and is characterized by a strong increase of C33 and C44 effective elastic constants (respectively, +83% and +70%). [ABSTRACT FROM AUTHOR]

Yttrium oxide, Y2O3, thin films are deposited in situ at 700 °C by laser ablation on MgO substrate. Orientation relationships are studied by means of asymmetric X-ray diffraction and HRTEM investigations. A particular attention is paid to the growth of the (1 0 0) orientation of the oxide which seems to be strongly related to the oxygen partial pressure in the deposition chamber. An explanation in terms of a particular dislocation configuration is proposed. This configuration is linked to the oxygen partial pressure through the atom mobility in the thin oxide film. [Copyright &y& Elsevier]

Issues on the superficial oxidation of mesoporous amorphous silicon and germanium photonic layers generated at oblique angles are reported. Such films were designed to improve the transmittance of optical elements over the mid-IR window (3.6–4.9 μm) by removing the light reflection. These nanostructures were deposited on silicon substrates by e-beam evaporation at room temperature. IR ellipsometry and spectrophotometry studies combined with models based on effective medium approximations predicted the presence of silicon or germanium oxides. Such oxidation was evidenced by combining X-ray photoelectron spectroscopy and advanced (scanning-)transmission electron microscopy studies based on energy-dispersive X-rays and electron energy-loss spectroscopies. Both techniques also allowed to prove the formation of core-shell-type architectures consisting of pure Si or Ge surrounded by oxidized species, even for a Ge layer subsequently capped with a dense MgF 2 coating. The different approaches used for preparing electron transparent specimens (tripod polishing and focused ion-beams) confirmed a fast oxidation of the Ge nanocolumns even for short air exposure periods, and allowed comparing it with the level of oxidation promoted from other pollutant sources. This work sheds light on the spontaneous undesired oxidation in Si or Ge slanted nanorods which can diminish the performances and limit further development of optical devices. Unlabelled Image • Si and Ge porous OAD thin films for optical applications in the infrared. • Optical characterization of the layers grown by ellipsometry and spectrophotometry. • Spontaneous formation of Si and Ge oxidized species predicted by the BEMA model. • Confirmation of the surface oxidation by compositional (S)TEM/EDX and XPS analyses. • Oxidized core-shell type structures evidenced by (S)TEM/EELS analyses at nanoscale. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of AlO x N y were deposited by magnetron sputtering in a wide composition range. Different structures and morphologies were observed, depending on the composition and bonding states, which opened the possibility to tailor the properties of this oxynitride system between those of pure Al and those of nitride and oxide films. In a wide range of stoichiometries, one can report the formation of nanocomposite porous films, where Al nanoparticles are dispersed in an amorphous matrix of AlO x N y . The electrochemical behaviour of the films was studied in isotonic NaCl solution. It was observed that the pitting potential characteristic of aluminium disappears with the incorporation of oxygen and nitrogen in the films, being replaced by a smooth current increase. Electrochemical impedance spectroscopy performed during 35 days showed that the corrosion resistance of the films steadily increases. The unusual optical reflectance profile of some films is maintained after immersion for several months. [Copyright &y& Elsevier]

• Sputtered indium tin oxide films on polyimide substrate are polycrystalline. • Films were strained in biaxial tension with in situ diffraction measurements. • The four indium tin oxide films are found to have a slight elastic anisotropy. • Electrical measurements show crack onset strains ranging from 0.15 to 0.3%. • O 2 flow during deposition delays crack onset as the temperature decrease does. Four series of Indium Tin Oxide (ITO) thin films 600 nm thick were deposited on polyimide substrates by Xe ion beam sputtering under different deposition conditions: with or without O 2 flow, and at room temperature or 100 °C heated substrates. Both electrical and mechanical properties of the four different films were investigated in situ by electrical resistance measurements and synchrotron x-ray diffraction during equibiaxial deformation tests. The ITO films are found to have a low elastically anisotropy, i.e. an elastic anisotropy index slightly smaller than 1. The elastic regime domain is quite small and is associated to a small effective negative gauge factor. During biaxial straining, electrical measurements show that all films are very brittle with crack onset strains corresponding to applied strains ranging from 0.15 to 0.3%. The introduction of oxygen flow during deposition delays the crack onset as the decrease of deposition temperature does. [ABSTRACT FROM AUTHOR]

Abstract: Y2O3 thin films deposited on (001)-MgO substrate have been investigated by high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy. Digital processing of the HRTEM images reveals the presence of grains with a crystallographic structure different from that of the rest of the film (Ia3). The spectrum imaging technique has been applied in vicinity of the Y2O3/MgO interface to get a better knowledge of the phases nucleated on the substrate surface. Fine structures of the O K-edge have been studied in detail; actually two kinds of spectra have been detected in the yttrium oxide thin film. These spectra have been compared to self-consistent full multiple scattering calculations (SC-FMS). One family of spectra has then been associated to the well-known Ia3 structure. The other family of spectra has been compared to calculations performed for the other known structures (such as hexagonal or monoclinic) of Y2O3 with a little success. We have finally compared these spectra to calculations performed with a particular atomic arrangement (octahedral) of Y and O atoms, which leads to a good match between experimental and calculated spectra. Our results emphasize the benefit of coupling several techniques such as HRTEM, EELS and SC-FMS for the determination of structures at the nanometric scale. [Copyright &y& Elsevier]