Effects of post annealing on structural, electrical and optical properties of ZnO:Al thin films prepared by RF magnetron sputtering

Abstract

Al doped ZnO (ZnO:Al, AZO) thin films were deposited on ordinary soda-lime glass (SLG) substrates by RF magnetron sputtering. Effects of post annealing (300~600 °C for 2~30 min in air and N₂, respectively) were studied. All the films were wurtzite structure with highly c-axis preferential orientation. Their electrical properties were relatively stable at the post annealing temperature of 300 °C. As the temperature further increasing, post annealing in air leaded to drastic degradation in the electrical properties, while that in N₂ had relatively small influence. Diffusion of alkali ions from SLG substrates was deduced to be one of the influence factors for electrical properties. The spectra measurements showed that the post annealing mainly affected the transmittance in the near-infrared and infrared (NIR-IR) range and the optical band gap (E_g). The variation of E_g was attributed to the Burstein-Moss (BM) shift modulated by many-body effects.