Effect of target substrate distance on the properties of RF sputtered PZT films

Lead zirconate titanate (PZT) films have been deposited by RF sputtering using an oxide target with excess lead oxide, on different substrates. The structural and optical properties have been studied as a function of target-substrate (T-S) distance and postdeposition annealing. The as-grown films were amorphous. On postdeposition annealing in an excess PbO+PZT atmosphere at 450°C, the films grown at a 4-cm T-S distance showed crystallinity, whereas films deposited at a higher T-S distance remained amorphous. The surface roughness and the film thickness decreased with increasing T-S distance. The as-grown films were highly transparent. The optical bandgap was estimated by plotting α² versus hυ and the value of the bandgap depended on the T-S distance. The fundamental absorption edge shifted to a lower wavelength when subjected to postdeposition annealing