X-Ray Diffraction Analyses of ZnO and (Zn, Mg)O Single Crystalline Films Epitaxially Grown on a-Plane Sapphire Substrates

Abstract

Precise X-ray diffraction analyses are performed on epitaxial ZnO and (Zn, Mg)O (0001) films with 50 nm thick cap layers grown on Sapphire (1120) substrates by molecular beam epitaxy method. The tilting of c-axis of ZnO and (Zn, Mg)O films is as small as 0.2 degree. In-plane X-ray diffraction analysis reveals directly the twisting of a-axis of films as smaller than 0.8 degree. Orientational misalignments between films and substrates are confirmed in the order of 1 degree both from out-of-plane and from In-plane Reciprocal space mapping measurements, together with the pseudomorphic coherent growth of cap layers. It is concluded that the lattice misalignment in the out-of-plane direction is affected by the miscut of substrate surface treatment.