Effects of ZnAl2O4 segregation in high temperature sintered Al-doped ZnO sputtering target on optical and electrical properties of deposited thin films

In this work, several Al-doped ZnO thin films were sequentially deposited from a high temperature sintered sputtering target in order to understand the effect of ZnAl2O4 segregation in target on optical and electrical properties of the deposited films. It was observed that the Al-doped ZnO films were all well (002) oriented with increasing 2θ from 34.25 to 34.38°, which corresponded to the lattice shrinkage from 5.232 Å to 5.212 Å. The corresponding band gaps for the Al-doped ZnO films increased from 3.47 eV to 3.54 eV as determined from transmittance spectra and the resistivity decreased from 3.7 × 10− 3 Ω cm to 1.3 × 10− 3 Ω cm. These changes were ascribed to the Al concentration increase from the polished surface to the inner target in the target due to surface segregation of ZnAl2O4 during the high temperature sintering process.