Effect of post annealing on the band gap of MgxZn1-xO thin films

In this work, Mg(x)Zn(1-x)O ( MZO) thin films were grown on quartz by rf magnetron sputtering technology. It was found that MZO films possess preferred c-axis orientation and exhibit hexagonal wurtzite structure up to a Mg composition of 44.26 mol%. Furthermore, the band gap determined by absorption spectra was smaller than the theoretical calculation for the as-grown MZO thin film. The band gap blueshifted initially and then redshifted with increasing the annealing temperature of the MZO films. The reason for the shift was attributed to the displacement, effusion of Mg atoms in the films and phase separation at different annealing temperatures.