Localization of Aluminum in ZnO:Al Layers during Magnetron Sputtering Deposition

The specific features of aluminum localization and the mechanism of formation of donor centers in ZnO:Al layers synthesized by rf magnetron sputtering have been investigated. It is shown that aluminum is mainly localized on intergranular boundaries of zinc oxide in the intrinsic oxide phase. The mechanism of Al oxidation on grain boundaries depends strongly on the oxygen content in the working chamber: during sputtering in a pure argon atmosphere with oxygen deficit, aluminum oxidation occurs as a result of the interaction of the surface layer of zinc oxide crystallites with oxygen, which leads to the formation of surface donor centers on grain boundaries. With an increase in partial oxygen pressure aluminum is mainly oxidized by the oxygen from the gas atmosphere, forming an intrinsic barrier phase on grain boundaries.