Effects of annealing conditions on the structural and electrical properties of a-oriented ZnO thin films

We studied the structural and optical properties of non-polar a-plane ZnO films grown on r-plane Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ substrates by RF-sputtering with different annealing conditions and oxygen partial pressure. Epitaxial relationships between the ZnO films and Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ substrates were determined by $\varphi $-scan to be ZnO[0001]//Al$_{\mathrm{2}}$O$_{\mathrm{3}}$[-1011], ZnO[1-100]//Al$_{\mathrm{2}}$O$_{\mathrm{3}}$[1-210]. Photoluminescence spectra showed that band gap depended on annealing times, which is sensitive to intrinsic emission and surface defects in the a-plane ZnO. Hall Effect were measured on all samples by a PPMS system to find the relations amount annealing times, carrier concentrations and mobilities.