ABSTRACT
Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.
ABSTRACT
Oxide-based materials have a variety of applications in chemical sensing and photocatalysis, thin-film transistors, complex-oxide field-effect transistors, nonvolatile memories, resistive switching, energy conversion, topological oxide electronics, and many others. The radiation resistance of these materials in such devices plays an important role in device operation in radiation environment, and this attracts much attention in the research area. In spite of damage in a number of cases high-energy particles may have a beneficial effect on the target. In this mini-review article examples of both creation of defects and beneficial changes in the structure and properties of homogeneous and nanostructured oxides caused by high-energy electron and neutron irradiation are given by considering some recently published results. First, the attention is turned to ionizing and displacement effects of electron and neutron irradiation in homogeneous bulk and thin-film oxides reported in the literature. Then, the effect of electron and neutron irradiation on nanostructured oxides and semiconductor nanoparticles embedded in an oxide matrix is regarded. Considerable attention is paid to silicon oxide layers since they are widely used in microelectronic products, which are among the most manufactured devices in human history. Processes of irradiation-induced lattice rearrangement, compositional changes, growth of nanoparticles and their size reduction, creation of point defects and their complexes, electron-hole generation, and charge trapping are discussed.
ABSTRACT
Selective UV sensitivity was observed in Metal-Oxide-Semiconductor structures with Si nanoclusters. Si nanocrystals and amorphous Si nanoparticles (a-Si NPs) were obtained by furnace annealing of SiOx films with x = 1.15 for 60 min in N2 at 1000 and 700 °C, respectively. XPS and TEM analysis prove phase separation and formation of Si nanocrystals in SiO2, while the a-Si NPs are formed in SiO1.7 matrix. Both types of structures show selective sensitivity to UV light; the effect is more pronounced in the structure with nanocrystals. The responsivity of the nanocrystal structure to 365 nm UV light is ~ 4 times higher than that to green light at 4 V applied to the top contact. The observed effect is explained by assuming that only short wavelength radiation generates photocarriers in the amorphous and crystalline nanoclusters.