Keywords: RF sputtering, ZnO thin films, annealing, growth mechanisms, renewable energy, optical properties, zinc oxide, transmittance, reflectance, absorbance, energy band gap, solar cells, refractive index, extinction coefficient
Growth mechanism and optical properties of zinc oxide thin film
Zinc oxide (ZnO) thin films were successfully deposited on glass substrate by radio frequency (RF) sputtering technique. One set of the samples was annealed in open air at temperatures of 423 K, 573 K and 723 K for one hour while another set of samples was annealed under nitrogen atmosphere for the same duration of time and temperature as the other set. A growth mechanism for thin film growth by RF sputtering has been presented. The films were also characterised to assess their optical properties. The ZnO thin films showed good transmittance, low reflectance and good absorbance in the visible region. The energy band gap (Eg) obtained is in the range of (3.15–3.28 eV) which is good for window layer of a solar cell. Other optical constants evaluated include refractive index and the extinction coefficient.