Structural Properties and Temperature Behaviour οf Optical Absorption Edge in Polycrystalline ZnO:X (Cu,Ag) Films

Silver- and copper-doped ZnO films were prepared by radio-frequency magnetron sputtering on glass substrates. The influence of dopants content on the structural, morphological properties as well as on evolution of the optical absorption edge was considered. It has been found that Ag- and Cu-doped ZnO films are characterized by wurtzite crystalline structure with the preferred direction of crystalline orientation (002). The sizes of grains within the films were found to be dependent on the type of dopant. The temperature evolution of the optical absorption edge is described by the modified Urbach rule that reflects polycrystalline nature of the material. The corresponding parameters concerning electron- (exciton-) phonon interaction, phonon energies and temperature changes of the band-gap were determined and analysed.