Effect of deposition time on sputtered ZnO thin films and their gas sensing application

Nowadays, advanced industrialization and population growth have led to increasing the environmental related issues. This paper reports the effect of deposition time on ZnO films deposited on to the glass substrate by using rf magnetron sputtering technique and their further use for gas sensing applications. Herein, deposition time is considered to be changed from 300 s, 800 s (S1, S2). The thickness of deposited films lies in the range of 130–180 nm. The synthesized films were characterized by various techniques in terms of structural, morphological, optical and gas sensing properties. The typical crystal size of ZnO films was found to be in the range of 15–27 nm. FESEM analysis revealed the growth of nanospheres was lies in the range of 80–120 nm. Fourier transform infrared spectroscopy confirmed the ZnO bonding located at a wavelength of 430 cm⁻¹. The average optical transmittance of the film was about 90–95% in the visible range. The optical band gap of ZnO films was decreased from 3.31 to 3.29 eV. The detailed characterization study showed 800 s is an optimum deposition time for good optoelectronic properties. For gas sensing application, highest sensitivity was obtained at operating temperature of 205 °C. Prepared films have a quick response and fast recovery time in the range of 128 s and 163 s respectively. These response and recovery time characteristics were explained by valence ion mechanism.