Nonpolar a-plane ZnO growth and nucleation mechanism on (1 0 0) (La, Sr)(Al, Ta)O3 substrate

Nonpolar a-plane ZnO epitaxial film with [1 1 −2 0] orientation was successfully grown on a (1 0 0) (La0.3,Sr0.7)(Al0.65,Ta0.35)O3 (LSAT) substrate by a chemical vapor deposition method. The dependence of surface morphologies and epi-film crystallinity on the growth temperature was studied by a scanning electron microscopy and X-ray diffraction. Room temperature photoluminescence spectra all exhibit a strong near-band-edge emission peak at 378.6 nm without noticeable green band. From high resolution transmission electron microscopy, we found two distinct growth configurations for our a-plane ZnO on (1 0 0) LSAT. To explain the epitaxial properties, we illustrate four possible nucleation sites on (1 0 0) LSAT for two kinds of orientational relationship, i.e. [1 0 −1 0]ZnO//[0 1 1]LSAT and [0 0 0 1]ZnO//[0 1 1]LSAT.