Improved epitaxy of ZnO films by regulating the layers of graphene

Abstract

Growth of ZnO film on graphene buffered sapphire substrate by plasma assisted molecular beam epitaxy (PAMBE) was investigated. Specifically, the surface morphology, crystal orientation and crystal quality of ZnO epitaxial layer and nucleation layer deposited on graphene with various thickness were analyzed by atomic force microscope (AFM), scanning electron microscope (SEM), high resolution X-ray diffraction (HRXRD), and high-resolution transmission electron microscope (HRTEM). The experiments showed that after buffered with double-layer graphene (DLG), six-fold symmetrical pits with the same orientation appeared on the successive ZnO film surface and the full width of half maximum (FWHM) of ZnO (002) plane rocking curve decreased to 769.3 arcsec. By comparing ZnO nucleation layer on graphene with different layers and checking the graphene by Raman spectroscopy, the mechanism for improving crystal quality of ZnO film grown on DLG was revealed. This study demonstrates the potential that high-crystal-quality ZnO film can be grown on graphene by plasma-assisted remote heteroepitaxy without limitation of the crystal mismatch and thermal mismatch between epitaxial film and substrate. It could be meaningful for the development of simplified growth technology of ZnO based films and devices.