Effects of annealing and supersonic treatment on the structure and photoluminescence of ZnO films

We have deposited ZnO thin films on the Si (10 0) substrate at 473 K using facing-target magnetron RF sputtering system and have investigated the effect of annealing and supersonic treatment on the structure and photoluminescence (PL) of ZnO thin films. The results showed that as-deposited ZnO thin film displayed a bad preferential C-axis (0 0 2) orientation. As the annealing temperature increased from 673 to 973 K, the preferential C-axis orientation changed to better gradually. Meanwhile, scanning electronic microscopy (SEM) observation showed that the as-deposited ZnO thin film grew in columnar form and the grain size was approximately from 20 to 50 nm. In addition, the PL spectrum showed that the as-deposited ZnO thin film had no emission peak. When the annealing temperature reached 673 K, a weak violet peak with 398 nm was observed. As the annealing temperature increased to 773 K, the intensity of the violet peak increased and an ultraviolet peak with 378 nm was observed. Besides, ZnO thin films annealed at various temperatures had no green emission peak, while for ZnO thin films annealed at 973 K and then treated by supersonic, a strong and wide green emission band was observed. (c) 2007 Elsevier B.V. All rights reserved.