Effect of symmetry of substrate surfaces on the orientation and growth mode of ZnO films

The growth behaviors of ZnO films prepared by laser molecular beam epitaxy (L-MBE) were investigated on the substrates with different symmetry. The growth mode, the out-of-plane and in-plane orientations of ZnO thin films have been estimated by in-situ reflected high-energy electron diffraction (RHEED) and ex-situ X-ray diffraction (XRD). ZnO films on amorphous glass substrates were polycrystalline with mixed (1 0 0) and preferred (0 0 1) crystal orientation. Single-domain ZnO films were arranged on (0 1 1)-, (1 1 1)-cubic perovskite and (0 0 1)-hexagonal substrates. On (0 0 1)-cubic perovskite surfaces, ZnO films contained poly-domain twined structure. The orientation difference of ZnO films could be attributed to the competition between the factors of the surface and interface influence including surface energy, strain energy and electrostatic energy. The crystal quality and growth mode were found to be dependent on not only the interface mismatch but also domain symmetry.