Special Issue Editorial: Functional Oxide Based Thin-Film Materials

Protective oxide coatings, such as Al2O3 and Y2O3 coatings, are widely used in semiconductor industries because of their hardness, high wear resistance, dielectric strength, high corrosion resistance, and chemical stability for plasma chambers [...]

method and the sol-gel method, which were deposited successfully on microscope glass substrates. In [7], Díaz-Becerril et al. have investigated the tantalum-doped ZnO structures synthesized on silicon substrates by using a hot filament chemical vapor deposition reactor. Green photoluminescence (PL) was observed by the naked eye when Ta-doped samples were illuminated by ultraviolet radiation and confirmed by photoluminescence spectra. The PL intensity on the Ta-doped ZnO increased from those undoped samples up to eight times and the resistivity and the sheet resistance also decrease when there is a greater amount of tantalum in the film.
An interesting investigation into the series of nanometer scale (33-70 nm) HfO 2 thin films grown on Si substrates under different conditions by atomic vapor deposition (AVD) is reported by Feng et al. in [8]. The comprehensive studies demonstrate that appropriate substrate temperature and oxygen flow are essential to the structure, chemical composition, and optical constants from the surface and interface of the HfO 2 films deposited by AVD. This work with integrated experiment measurements and analyses has enhanced our understanding of AVD-grown HfO 2 advanced materials.
An entirely different perspective on thin film oxides is presented by Chang and Chan. In their paper, [9], they investigated the heavily doped wide band gap semiconductors like aluminum-doped zinc oxide (AZO) and tin-doped indium oxide (ITO) for low emissivity glass (low-e glass), which is often used in energy-saving buildings. The emissivity and average visible transmittance for H 2 /N 2 = 100/100 plasma annealed AZO/ITO were 0.07% and 80%, respectively, lying in the range of commercially used low emissivity glass.
Supercapacitors, excellent energy storage devices, can effectively alleviate the current energy crisis. Based on their obvious advantages, such as simple design, high-power density, a long cycling lifetime, and a short charge/discharge rate, supercapacitors have attracted much research interest in recent years. Zheng and co-workers in [10] have synthesized a NiO@ZnO (NZO) hybrid with different reaction times by a green hydrothermal method. A highest energy density of 27.13 Wh kg −1 can be achieved at a power density of 321.42 W kg −1 . These desirable electrochemical properties demonstrate that the NZO hybrid is a promising electrode material for a supercapacitor.
Finally, we also presented a contribution concerned with a review article, using 1D zinc oxide (ZnO) as a representative nanomaterial [11]. This article reviews the fabrication methods of 1D ZnO nanostructures-including chemical vapor deposition, hydrothermal reaction, and electrochemical deposition-and the influence of the growth parameters on the growth rate and morphology. Important applications of 1D ZnO nanostructures in optoelectronic devices are described. Several approaches to improve the performance of 1D ZnO-based devices, including surface passivation, localized surface plasmons, and the piezo-phototronic effect, are summarized.
To conclude, I believe that this Special Issue on Functional Oxide-Based Thin-Film Materials touches on the latest advancements in several aspects related to material science: the synthesis of novel oxide, photoluminescence characteristics, photocatalytic ability, energy storage, light emitter studies, low emissivity glass coatings, and investigations of both nanostructure and thin film properties. I wish to express my deepest and sincere gratitude to all authors who contributed, for having submitted manuscripts of such excellent quality. I also wish to thank the Editorial Office of Crystals for the fast and professional handling of the manuscripts during the whole submission process and for the help provided.

Conflicts of Interest:
The authors declare no conflict of interest