Study of solid solubility of gold doped in ZnO films and its effect on optical properties

Gold-doped ZnO (ZnO:Au) thin films with different Au content were fabricated by radio frequency magnetron sputtering and post annealing techniques. The solid solubility of Au in ZnO was found smaller or equal to 1.00 at.% for the ZnO:Au annealed at 350 C. X-ray photoelectron spectroscopy (XPS) results suggest that Au exists in ZnO:Au with chemical state of AuZn´+ while the Au content is 1.00 at.%, once the Au content is larger than 1.00 at.%, Au exists in the ZnO with chemical state of metallic Au in the grain boundary and AuZn1+ in the ZnO:Au. While the incorporation of Au in the ZnO films seem to quench both the band edge and visible emissions of the ZnO films, and the degree of photoluminescence quenching increases with the increasing Au content. PL quenching of the ZnO:Au is attributed to the substitutional doping of Au in the ZnO films, while the degree of quenching may related to the content of metallic Au in the ZnO:Au.