Influence of Ag-S codoping on silver chemical states and stable p-type conduction behavior of the ZnO films

摘要

The effects of Ag-S codoping on chemical states of Ag doped in ZnO, as well as electrical and optical properties of the ZnO film were investigated by comparative study of undoped ZnO, Ag-doped ZnO (ZnO:Ag) and Ag-S codoped ZnO (ZnO:(Ag, S)) films. It was found that the Ag occupied the Zn site and showed only positive univalence (Ag_(Zn)~(1+)) in the ZnO:(Ag, S). Compared to the ZnO: Ag, the solid solubility of the Ag_(Zn)~(1+) is greatly enhanced in the ZnO: (Ag, S) with incorporation of S. Stable p-type conduction was observed and proved further in the ZnO: (Ag, S) films. Low temperature photoluminescence measurement for the ZnO:(Ag, S) indicated that there were two kinds of acceptors of Ag_(Zn)~(1+)-So complex and Ag_(Zn)~(1+) in the ZnO:(Ag, S), moreover, the ionization energy of the Ag_(Zn)~(1+)-So was smaller than that of the Ag_(Zn)~(1+). The stable p-type conduction of the ZnO:(Ag, S) was suggested to be attributed to the increase of the Ag_(Zn)~(1+) content induced by S doping and to the formation of the Ag_(Zn)~(1+)-So complex acceptor.