Effect of substrate bias on crystal structure and thermal stability of sputter-deposited ZnO films

The ZnO films were deposited, respectively, in Ar and Ar/O2 in order to investigate the effects of positive ions bombardment of argon and oxygen on both the crystallinity and thermal stability of sputtered ZnO films. The TEM and XRD results indicate that crystallite size of the ZnO film increased by the substrate bias as the film deposited in Ar. On the other hand, the preferred orientation of the film was changed from (0 0 2) to (1 0 0) and (1 0 1) by the substrate bias as the film deposited in Ar/O2. The thermal stabilities of zinc (Zn) and molecular oxygen (O2) in the ZnO films were investigated by thermal desorption spectrometry. The Zn desorption was drastically suppressed by the Psub when the ZnO film deposited in Ar/O2. The substrate bias effectively suppressed the Zn desorption when the film deposited in Ar/O2. Grain boundaries play an important role in determining the Zn desorption from the films.