Establishing the mechanism of thermally induced degradation of ZnO:Al electrical properties using synchrotron radiation

X-ray absorption near edge structure and x-ray diffraction studies with synchrotron radiation have been used to relate the electrical properties of ZnO:Al films to their bonding structure and phase composition. It is found that Al-sites in an insulating metastable homologous (ZnO)3Al2O3 phase are favored above a certain substrate temperature (Ts) leading to deterioration of both the crystallinity and the electrical properties of the films. The higher film resistivity is associated with lower carrier mobility due to increased free electron scattering. Lower metal to oxygen flux ratios during deposition expand the range of Ts at which low-resistivity films are obtained.