Studies on Single Step Deposition of ZnO Nanostructured Thin Films for Sensing and Photocatalysis Application

Abstract

ZnO, band gap of ~3.37eV, is a chemical stable, biocompatiable, non-toxic n-type semiconductor material. Due to advancement of microfabrication technology and chemical synthesis method, nanostructured ZnO are found to be in different shapes and morphologies such as, nanorods, tetrapods, nanowires, nanoparticles, hollow sphere, nano/microflowers, nanocage, nanobelts, nanosheets, nanoflakes, thin films etc. Nanostructure of ZnO improves the sensors and devices sensitivity and detection limits due to its higher surface to volume ratio. Most of these nanostructures are synthesized by hydrothermal method which has limitations like fewer yields, required one seed layer to grow the different nanostructured thin film and finally this method cannot be implemented on large scale wafer. Other expensive equipment like sputtering, e-beam, thermal evaporation able to deposit large area but they are a unable to deposit nanostructured thin film .Only thin films are deposited using these systems. Therefore there is a need to develop a low cost method to deposit nanostructured thin films on large areas. We have used a homemade ultrasonic spray pyrolysis system to grow different ZnO nanostructured (microflower, thin films, nanorods, nanosheets,porous structures) thin films in a single deposition step on different substrates like glass, stainless steel mesh, polyamide, Si. Among all the structures there are very few literature available on microflower based sensors and devices. We have thus studied the microflower structured thin film on different substrates for different applications like UV detector, photocatalysis (methylene blue degradation) and SERS as dye, pesticides, explosives and biomolecule detections.