[en] 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 3.8 eV.

[en] BN films were deposited by using a mixture of nitrogen and argon ions for assistance during growth. On condition that the nitrogen-to-boron flux ratio should be high enough to synthesize stoichiometric material, tetrahedral bonds in BN films are formed when the argon-to-boron flux ratio and accelerating voltage exceed interdependent threshold values, which depend slightly on incident angle of the beam, but not on the substrate temperature above 200 C. The fraction of cubic phase in films is maximized for energies less than 300 eV and Ar-to-B flux ratios higher than one. Computer simulations of the deposition process seem to indicate that threshold conditions are connected with a threshold number of displacements per deposited atom and that collisions which transfer recoil energies lying in the range 0-50 eV are favorable to the formation of sp³ bonding, while those leading to higher energy values are detrimental. This explains why the very surface of a growing film remains in the trigonal form for beam energies greater than 200 eV. (orig.)

[en] In this work, chromium thin films were deposited using dcMS and HiPIMS technologies. To compare these technologies, we analyzed the ion flux and the Cr coating microstructure in the same plasma conditions. Ion flux was measured with a mass spectrometer in time-averaged for both discharge and time-resolved for HiPIMS discharge. Time-averaged measurements provided important information. First, the low energetic part of the ion energy distribution function (IEDF) was similar in dcMS and HiPIMS and second the high energetic component was more prominent in the HiPIMS discharge. Time-resolved measurements showed that the high energetic part of the ion flux reached the mass spectrometer faster than the lowest part. It is only after the pulse end that most of the thermalized ions arrived and then cooled the flux. The correlation of these results with microstructure analysis shows that energetic particles induced a higher film density and a smoother surface in HiPIMS compared to dcMS discharge. (authors)

[en] 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^o-33^o range) which can be attributed to (100) orientation. Finally, the influence of compressive stress and ion bombardment on the change of orientation is discussed

[en] Highlights: • Hexagonal AlN phase presents a fiber (0001) with a tilted c-axis for DCMS method. • In the case of HiPIMS method, the (0001) fiber is perfect, with a low dispersion. • The texture analysis allows the characterization of the cubic phase of AlN. • Existence of different oriented crystallites of cubic AlN phase from {100} to {111}. • Misfit's calculations confirm the easier growth of hexagonal AlN on cubic AlN layer. - Abstract: 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.

[en] Zinc oxide (ZnO) nanostructures are very attractive in various optoelectronic applications such as light emitting devices. A fabrication process of these ZnO nanostructures which gives a good crystalline quality and being compatible with that of micro-fabrication has significant importance for practical application. In this work ZnO films with different thicknesses were deposited by RF-sputtering on vertically aligned multiwalled carbon nanotube (MWCNTs) template in order to obtain ZnO nanorods. The obtained hybrid structures (ZnO/MWCNTs) were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and time resolved photoluminescence spectroscopy (PL). Results show that the ZnO/MWCNTs have a nanorod structure like morphology with a good crystalline quality of the deposited ZnO on the MWCNTs. PL measurements reveal an enhancement of the band edge signal of ZnO/MWCNTs which is three times of magnitude higher compared to the ZnO film deposited on silicon. Moreover, the intensity enhancement varies as function of the ZnO thickness. Such hybrid structures are promising for optoelectronic application, such as blue–violet sources.

[en] Low-temperature Aluminum Nitride (AlN) thin films with a thickness of 3 μm 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. - Highlights: ► Aluminum Nitride sputtering technique with a low temperature growth process ► Epitaxial quality of two microns sputtered Aluminum Nitride film ► Optics as a non-destructive accurate tool for acoustic wave investigation

[en] ZnO films were deposited on Si substrate by RF-sputtering using titanium nitride (TiN) as buffer layer that was deposited at different thicknesses: 160 and 2290 nm. Despite the lattice mismatch of up to 6.35% between ZnO and TiN, the ZnO films deposited on TiN buffer layers show enhanced near-band-edge photoluminescence (PL) emission at room temperature which is two times higher of magnitude than those grown directly on Si. The PL enhancement intensity, provided by TiN buffer introduction, is attributed to the improvement of ZnO crystalline quality and stoichiometry. The use of a good electrical conductor which has high thermal stability like TiN as buffer layer for the blue emission enhancement of ZnO would make it promising for optoelectronic applications. - Highlights: ► Use of TiN buffer layer for blue emission enhancement of ZnO films is reported. ► The near-band edge photoluminescence intensity of buffered ZnO films is doubled. ► Raman, X-ray diffraction and X-ray photoelectron spectroscopy analyses are correlated

[en] Bi_4-xLa _xTi₃O₁₂ (BLT _x) (x = 0 to 1) thin films were grown on silicon (100) and platinized substrates Pt/TiO₂/SiO₂/Si using RF diode sputtering, magnetron sputtering and pulsed laser deposition (PLD). Stoichiometric home-synthesized targets were used. Reactive sputtering was investigated in argon/oxygen gas mixture, with a pressure ranging from 0.33 to 10 Pa without heating the substrate. PLD was investigated in pure oxygen, at a chamber pressure of 20 Pa for a substrate temperature of 400-440 deg. C. Comparative structural, chemical, optical and morphological characterizations of BLT thin films have been performed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Photoelectron Spectroscopy (XPS), Spectro-ellipsometric measurements (SE) and Atomic Force Microscopy (AFM). Both sputtering techniques allow to obtain uniform films with thickness ranging from 200 to 1000 nm and chemical composition varying from (Bi,La)₂ Ti₃ O₁₂ to (Bi,La)_4.5Ti₃O₁₂, depending on deposition pressure and RF power. In addition, BLT films deposited by magnetron sputtering, at a pressure deposition ranging from 1.1 to 5 Pa, were well-crystallized after a post-deposition annealing at 650 deg. C in oxygen. They exhibit a refractive index and optical band gap of 2.7 and 3.15 eV, respectively. Regarding PLD, single phase and well-crystallized, 100-200 nm thick BLT films with a stoichiometric (Bi,La)₄Ti₃O₁₂ chemical composition were obtained, exhibiting in addition a preferential orientation along (200). It is worth noting that BLT films deposited by magnetron sputtering are as well-crystallized than PLD ones