Study of the structural evolution in ZnO thin film by in situ synchrotron x-ray scattering

Abstract

The evolution of surface roughness and strain relaxation as a function of film thickness of ZnO films grown on sapphire(0001) were studied by in situ synchrotron x-ray scattering and atomic force microscopy measurements. The well-aligned two-dimensional (2D) planar layer dominated in layer-by-layer growth at the highly strained initial growth stage. As the film thickness increased, the discrete nucleations on the 2D planar layer continuously grew until the ZnO film reached the strain relaxed steady-state regime. When the 3D islands were quickly developed by the strain relaxation, the dynamic scaling exponent β was roughly 1.579. The strain relaxed steady-state regime was described as β∼0.234.