Structural variation of cubic and hexagonal Mg _x Zn _1-xO layers grown on MgO(111)/c -sapphire

We report on the structure study of Mgx Zn1-x O films and, in particular, we will focus on Mgx Zn1-x O layers with x=0.28 and 0.41 Mgx Zn1-x O layers with different crystal structures of cubic and wurtzite that have been grown by plasma-assisted molecular-beam epitaxy on MgOc -sapphire with MgZn flux ratio control. The Mgx Zn1-x O films have been characterized by high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction. The dependence of the cation-anion bond length to Mg content has been studied. A virtual crystal model of MgZnO has been applied to interpret the bond-length variation. HRTEM results indicate that the initial stage of the MgZnO growth on a MgO buffer layer starts with a cubic structure even in the case of a wurtzite structure at the end of growth.