Effect of Deposition Pressure on the Properties of ZnO Films on Teflon Substrate by RF Magnetron Sputtering

Nowadays, a lot of flexible and lightweight devices are needed in some electronics applications. In this paper, zinc oxide (ZnO) films were deposited on flexible Teflon substrates by radio frequency (RF) magnetron sputtering, and the influence of Ar pressure on the structure, residual stress and photoluminescence (PL) spectra properties was also studied. The results show that all the films have a polycrystalline microstructure with dominated (002) orientation. The best (002) c-axis orientation and largest grain size are observed in the films deposited at highest Ar pressure of 4Pa. It is found that all the ZnO films exhibit compressive stress. At lower Ar pressure, the stress is very small and increases with the increasing Ar pressure from 0.5 Pa to 1.5 Pa. However, at higher pressure, the stress decreases abruptly as Ar pressure increases from 2.0 Pa to 4.0 Pa. All samples have presented road deep-level (DL) emission in the visible range between 450 nm and 500 nm. The UV emission can only be found in the films with smaller stress. Furthermore, the intensity of the UV emission and visible luminescence is weaker in the films deposited at lower Ar pressure compared with those at higher pressure. The best (002) c-axis orientation and the deduction of the stress in the films deposited at 4Pa are believed to be associated with more efficient UV PL emission. Another possible reason for the strong UV emission in the films of 4.0 Pa may be ascribed to the larger grains.