Effect of annealing temperature on response time of ZnO photoconductor fabricated using thermal evaporation technique

Abstract

ZnO has been deposited on SiO2/Si substrate using thermal evaporation technique. Further, the deposited ZnO thin film has been annealed at 400 °C, 600 °C, and 800 °C separately. The deposited ZnO thin films have been characterized using Ultraviolet-visible Diffuse Reflectance Spectroscopy (UV–vis DRS), Atomic force microscopy (AFM), x-ray diffraction (XRD) technique, and Scanning electron microscopy (SEM). The deposited ZnO thin films have multiphase structures of ZnO such as hexagonal, unknown and cubic. UV-visible spectra of deposited films show absorbance edges in UV and visible regions. The average particle size of non-annealed ZnO is ∼60 nm, whereas annealed ZnO (at 800 °C) is ∼124 nm. The average surface roughness of ZnO sample annealed at 800 °C is lower than that of non-annealed ZnO sample and ZnO samples annealed at 400 °C and 600 °C. Sputtering technique has been used to make gold contact on ZnO film for testing the photoconductivity property. The rise time of ZnO photoconductor annealed at 800 °C (Tr = 0.04 s) is very fast as compared to that of all other ZnO photoconductors prepared using non-annealed ZnO sample and ZnO samples annealed at 400 °C and 600 °C.