Reactive RF magnetron sputtering epitaxy of NiO thin films on (0001) sapphire and (100) MgO substrates

Epitaxial growths of NiO thin films were realized on (0001) sapphire and (100) MgO substrates by using a reactive RF magnetron sputtering method. The NiO epilayers grown on a (0001) sapphire exhibited the (111)-oriented double-domain structure, which comprised of a triangular and its inverted triangular grains. Meanwhile, the NiO epilayers on a (100) MgO exhibited the (100)-oriented single-domain structure, which comprised of quadrangular grains. The observed grain structures most likely reflect the growth planes of respective NiO epilayers, and, mixed crystals of NiO and MgO were present near the interface. Therefore, A (100) MgO substrate is suitable for obtaining a single-domain NiO epilayer, whereas a (0001) sapphire substrate is suitable for obtaining a NiO epilayer without interdiffusion between NiO and sapphire. These NiO epilayers will be expected for applying the physical properties evaluation using photoluminescence or Hall measurements, and the fabrication of electrical or optical devices.

Enhancement of SnO2 for gas sensing applications

Thin films of SnO2 were deposited by reactive RF magnetron sputtering. It was shown that the films possess gas sensitivity to ethanol vapor at room temperature. XRD, SEM, and EDX measurements of thin films were investigated. Annealing of SnO2 thin films at 800 °С is polycrystalline and grain size of SnO2 in the range about 12 nm. The growth of SnO2 with annealing to 800 °C leads to the percolation nanorods structure. EDX clearly explains the rich of Sn reached 70% annealing. The conductivity of SnO2 nanorods has been increasing at room temperature for ethanol vapors.

Cu 4O3 thin films deposited by non-reactive rf-magnetron sputtering from a copper oxide target

Copper oxide thin films deposited by sputtering are frequently formed by using metal copper targets in reactive atmospheres. In this report, paramelaconite (Cu4O3) thin films were deposited by non-reactive rf magnetron sputtering. The target used for sputtering was a copper oxide disk fabricated by oxidation of metal copper at 1000 °C for 24 h in airatmosphere. X-ray diffraction (XRD) results showed that the copper oxide target was mainly composed of cupric oxide (CuO) and cuprous oxide (Cu2O) crystals. Raman analyses suggested that the surface of the copper oxide disk is composed by a (CuO) layer. XRD measurements performed to the copper oxide thin films deposited by non-reactive rf magnetron sputtering showed that the film is composed of (Cu4O3) crystals. However,Raman measurements indicated that the Cu4O3 thin films are also composed by amorphous CuO and Cu2O.

Influence of Reactive Oxygen Gas on Sputtered-Vanadium Oxide Films under Post-Annealing in Vacuum

Vanadium oxide thin films were deposited on glass substrates by O2 reactive-RF magnetron sputtering from a vanadium (V) target without substrate-heating. The percentages of O2 gas were 10%, 7.5%, 6.0%, 5.0% and 2.5%. The total gas flow rate (O2/Ar) was kept at 25 sccm. As-deposited films were experienced post-annealing process at different temperatures and times. The crystallinity and chemical bonding states of films were examined by X-ray diffraction and Raman spectroscopy. The condition in annealing to active crystallinity depended on an earlier composition of the films. As O2-gas percentages were 10% and 7.5%, after annealing, the as-deposited VxOy films were transformed into crystalline V2O5 films. With decreasing in O2 percentage to 5.0% and 2.5%, the films were transformed into V2O3 and VO films, respectively. The films deposited with 6.0% O2 were crystallized to VO2 with phase B after annealing with 500 °C 15 h. By applying a longer time to 30 h at the high temperature 500 °C in annealing, VO2 films revealed only phase M formation.

Surface Wettability of ZnO-Loaded TiO2 Nanotube Array Layers

Herein we report on the synthesis and the effects of gradual loading of TiO2 nanotube array layers with ZnO upon surface wettability. Two-step preparation was chosen, where TiO2 nanotube layers, grown in a first instance by anodization of a Ti foil, were gradually loaded with controlled amounts of ZnO using the reactive RF magnetron sputtering. After crystallization annealing, the formerly amorphous TiO2 nanotubes were converted to predominantly anatase crystalline phase, as detected by XRD measurements. The as-prepared nanotubes exhibited a well-aligned columnar structure, 1.6 μm long and 88 nm in diameter, and a small concentration of oxygen vacancies. Ti2+ and Ti3+ occur along with the Ti4+ state upon sputter-cleaning the layer surfaces from contaminants. The Ti2+ and Ti3+ signals diminish with gradual ZnO loading. As demonstrated by the VB-XPS data, the ZnO loading is accompanied by a slight narrowing of the band gap of the materials. A combined effect of material modification and surface roughness was taken into consideration to explain the evolution of surface super-hydrophilicity of the materials under UV irradiation. The loading process resulted in increasing surface wettability with approx. 33%, and in a drastic extension of activation decay, which clearly points out to the effect of ZnO-TiO2 heterojunctions.