Zinc Oxide Thin Films: Synthesis and Photocatalytic Applications

Abstract

The upcoming chapter explores zinc oxide (ZnO) thin films, examining their crystalline and optical properties. It discusses various deposition techniques for creating thin films, defined as layers from nanometers to micrometers thick, used in electronics, optics, and coatings. Thin film deposition methods, crucial for controlling film thickness and properties, include physical vapor deposition (PVD), sputtering, thermal evaporation, electron beam evaporation, and pulsed laser deposition (PLD). These techniques are vital in electronics, optics, and materials research. The chapter also covers ZnO thin films’ applications, emphasizing their photocatalytic abilities. ZnO has a large bandgap energy (3.37 eV), making it effective in UV light absorption and photocatalytic reactions. Upon UV photon absorption, ZnO generates electron-hole pairs, leading to efficient redox processes. ZnO’s chemical stability ensures lasting photocatalytic activity, resisting degradation under harsh conditions. It can be formed into nanostructures like nanoparticles, nanowires, and nanosheets, increasing surface area and catalytic efficiency. ZnO generates reactive oxygen species (ROS) like hydroxyl radicals, superoxide radicals, and hydrogen peroxide during photocatalysis. These ROS degrade organic pollutants, functionalizing substrates to break down fertilizers, pesticides, pharmaceuticals, nitrates, and pollutant gases such as nitrogen oxides and benzene compounds.