Deposition and Optical Characterization of ZnO Thin films on Glass Substrate

Abstract

ZnO is a wide band gap (3.37 eV) compound semiconductor which can be used in short wavelength optoelectronic devices.Here in this work we chose spin coating method as growth mechanism as it is simple, less expensive and in addition film uniformity is maintained in this method.In the growth process zinc acetate dihydrate, iso-propanol and monoethanolamine were used for producing Sol-gel Solution.The prepared solution was kept for 3 days (44 h) and 7 days (188h) for aging. After deposition, optical characterization has been performed by UV-VIS-Spectrometry The Transmittance values of the films deposited at the speeds of 2500 rpm (with 44 h aged solution) and 3500 rpm (with 188h aged solution) are at the range of 70-73% and the Energy band gaps of the films are 3.1 eV and 3.25eV, respectively. Whereas films deposited at the speed of 4000 rpm shows 86%transmittance and band gap energy of 3.3 eV which is much closer to the optimum value of 3.37 eV. Lower absorption values have been shown for higher coating speed.So with the increase in coating speed,the transmittance and the band gap both are increased. Also we can see that there is very negligible effect of aging time on optical properties of deposited films.