Surface localization of the Er-related optical active centers in Er doped zinc oxide films

Abstract

Er-doped ZnO films were grown on c-plane sapphire by employing the pulsed laser deposition method. In accordance with the previously reported literature studies, post-growth annealing was required to activate the optical emission originated from the intra-shell transitions of the Er atoms. Importantly, the present systematic studies revealed that the thermal activation of the optical activity is due to the atomistic rearrangements occurring only in the vicinity of the film surface. The processes exhibit a distinct signature of changing oxygen coordination with the Er atom, as observed by the x-ray photoemission study.