The effect of homo-buffer layer thickness on the crystalline quality and the surface roughness of ZnO thin film was investigated. ZnO thin films were prepared on (0001) sapphire substrates with different homo-buffer layer thickness of 20~60 nm by a radio-frequency magnetron sputtering method. The buffer layers were deposited at a substrate temperature of 400 οC and then main ZnO films were grown on the buffer layers at 600 οC. For comparison, single-layered ZnO films without buffer layer were prepared at substrate temperatures of 400 οC and 600 οC, respectively. Compared to the films without buffer layer, the films with buffer layer exhibited higher crystalline quality and surface smoothness. For the ZnO films with buffer layer, the transmittance spectra exhibited a steep fall-off at 380 nm, which is a characteristic of high quality ZnO film. The highest ZnO film quality was obtained for the film prepared with a buffer layer thickness of 20 nm, from which it is suggested that the crystalline quality and surface smoothness of ZnO film are improved as the buffer layer thickness decreases.

Keywords: ZnO thin film, Homo-buffer layer, Buffer layer thickness, Crystalline quality