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Abstract: In this work, polycrystalline aluminum doped zinc oxide (ZnO:Al) films with c-axis (002) orientation have been grown on glass and silicon substrates by RF (radio frequency) magnetron sputtering technique, at room temperature. A systematic study of the effect of sputtering deposition parameters (i.e. RF power and argon gas pressure) on the structural, optical and electrical properties of the films was carried out. We observed that, with increasing RF power the growth rate increased, while it decreased with increasing gas pressure. As mentioned above, the films were polycrystalline in nature with a strong preferred (002) orientation. The intrinsic compressive stress was found to decrease with both increasing RF power and gas pressure, and near stress-free film was obtained at 200W RF power and 2×10−1 Pa gas pressure. The obtained ZnO:Al films, not only have an average transmittance greater than 90% in the visible region, but also have an optical band gap between 3.33 and 3.47eV depending on the sputtering parameters. Moreover, a low value of the electrical resistivity (~1.25×10−3 Ωcm) was obtained for the film deposited at 200W and 2×10−3 mbar. [ABSTRACT FROM AUTHOR]

In this work we are interested in analyzing the texture of aluminum nitride thin films deposited by direct-current magnetron sputtering and high-power impulse magnetron sputtering on silicon (100) substrates. The texture characterization of aluminum nitride films was performed by X-ray diffraction. The pole figures have indicated that in both methods direct-current magnetron sputtering and high-power impulse magnetron sputtering, the microstructure is a (0001) strong fiber texture, with a tilted c-axis in the case of direct-current magnetron sputtering. Moreover, the texture analysis allowed the characterization of the cubic phase of aluminum nitride, which most likely constitutes a transition layer between the hexagonal aluminum nitride and the silicon substrate. The misfits' calculations between the different structure cells (silicon, hexagonal aluminum nitride and cubic aluminum nitride) confirm that the growth of the hexagonal aluminum nitride in the form of (0001) fiber is facilitated by this transition layer. [ABSTRACT FROM AUTHOR]

Abstract: Low-temperature Aluminum Nitride (AlN) thin films with a thickness of 3μm were deposited by Direct-Current magnetron sputtering on sapphire substrate. They present optical properties similar to those of epitaxially grown films. Different characterization methods such as X-Ray Diffraction, Transmission Electron Microscopy and Atomic Force Microscopy were used to determine the structural properties of the films such as its roughness and crystallinity. Newton interferometer was used for stress measurement of the films. Non-destructive prism-coupling technique was used to determine refractive index and thickness homogeneity by a mapping on the whole sample area. Results show that AlN films grown on AlGaN layer have a high crystallinity close to epitaxial films, associated to a low intrinsic stress for low thickness. These results highlight that it is possible to grow thick sample with microstructure and optical properties close to epitaxy, even on a large surface. [Copyright &y& Elsevier]

Abstract: In this paper, we characterize high transparency p-type semiconducting NiO thin films deposited by Direct Current Reactive Magnetron Sputtering from a pure Ni target in a mixture of oxygen and argon gases on Corning glass/SnO2:F substrates at different oxygen contents ranging from 0% at 30%. The influence of the O2/Ar ratio and thickness on transmittance has been examined using ultraviolet–visible spectroscopy. The results show that whatever the oxygen proportion into the discharge, the nickel oxide films exhibit a polycrystalline structure. At low oxygen content, the preferential orientation is (111), for stoichiometric films the XRD diagram is powder-like whereas the preferential orientation is (200) for higher oxygen content. For low and high oxygen content, the transmittance is low. Thanks to plasma method and its ability to tune the oxygen content in the discharge and therefore the film composition, we have been able to explore carefully the intermediate zone and obtain transparent films. The optical absorption coefficient α has been calculated from the transmittance and the variation of (αhν)2 versus the photon energy (hν) for nickel oxide is presented. The optical band gap energy has been evaluated and varies from 3.2 to 3.8eV. [Copyright &y& Elsevier]

Abstract: Mo(Cr) thin films were deposited by an Ionized Physical Vapor Deposition process i.e. Ionized Magnetron Sputtering (IMS). This deposition technique enables to ionize the neutral metallic sputtered species by a secondary plasma generated through a radio-frequency (RF: 13.56 MHz) powered coil. Thus, by acting on the substrate bias voltage, on the argon pressure and on the RF power applied to the coil, the ion energy and flux onto the substrate can be controlled. Various types of microstructure are then obtained, leading to a wide range of residual stresses in films from compressive to tensile. The control of both the microstructure and the related stress using the IMS process offers new opportunities in elaborating stress-engineered micro-objects for micro-electromechanical systems (MEMS). Residual stresses in the whole volume of the film were measured ex situ by Stoney curvature method and X-ray diffraction was applied to get the in-grain contribution (i.e. the crystallites) to the total residual stresses using the sin2 ψ  method. Besides, the grain morphology and local structure of the film were characterized by transmission electron microscopy. Relationship between synthesis conditions, microstructure, film morphology and residual stresses in Mo(Cr) films deposited by IMS is presented in this study and leads to a multi-scale description of the mechanisms of stress formation. The stress values determined from both techniques may be explained thanks to the analyzed morphological and microstructural features in the films. [Copyright &y& Elsevier]

Abstract: Piezoelectric AlN thin films were deposited on Silicon substrates by triode reactive sputtering. The variation of residual stress versus bias voltage on the substrate was investigated. A compressive stress was always observed with a maximum value for a negative substrate bias of 50 V. For higher negative bias voltage values, the compressive stress decreases. X-ray diffraction measurements showed two kinds of growth orientation. First, without bias voltage, films are well crystallized and (002) oriented. Second, with bias voltage, the (002) orientation disappears and a small peak appears (situated in the 2θ =32°–33° range) which can be attributed to (100) orientation. Finally, the influence of compressive stress and ion bombardment on the change of orientation is discussed. [Copyright &y& Elsevier]