Investigation of ZnO/sapphire interface and formation of ZnO nanocrystalline by laser MBE

Epitaxial ZnO thin films were prepared on atomically flat sapphire (α-Al2O3) (0001) substrates at various substrate temperatures by laser molecular beam epitaxy. Crystal structure was analyzed by four-circle X-ray diffraction. Atomic force microscope (AFM) and reflection high energy electron diffraction (RHEED) were used to evaluate surface morphology. When ZnO was deposited on atomically flat sapphire (0001), an epitaxial ZnO film was grown with c-axis orientation, having two different in-plane orientation, ZnO [1010]∥sapphire [1010] (400–450°C) and ZnO [1010]∥sapphire [1120] (800–835°C), depending on deposition temperature. The detailed observation of the initial growth of ZnO film deposited at 835°C revealed that the growth mode followed Stranski–Krastanov growth mechanism.