Growth of ZnO/Zn1-xMgxO multilayer thin films by pulsed laser ablation

ZnO/Zn$_{1-x}$Mg$_{x}$O multilayer thin films were grown on a-plane Al$_{2}$O$_{3}$ substrates at 400 $^{o}$C by pulsed laser ablation. Multilayer films were grown by stacking alternate layers of ZnO and ZnMgO with equal thickness varying from 2 to 8 nm. These films were characterized by x-ray diffraction, cathodeluminescence, and photoluminescence measurements. ZnO/Zn$_{0.9}$Mg$_{0.1}$O multilayer films showed a clear six-fold symmetry without in-plane rotational domains from pole-figures of X-ray diffraction. Decreasing the thickness of both ZnO and ZnMgO layers affected the band gap energy and optical properties. In particular, the band gap energy increased continuous with decreasing thickness of the ZnO and ZnMgO layers. A ZnO/MgO film was also grown by sequentially stacking ZnO and MgO layers and the resulting band gap energy was about 3.8 eV.