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

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 (AgZn1+AgZn1+) in the ZnO:(Ag, S). Compared to the ZnO:Ag, the solid solubility of the AgZn1+AgZn1+ 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 AgZn1+–SOAgZn1+–SO complex and AgZn1+AgZn1+ in the ZnO:(Ag, S), moreover, the ionization energy of the View the MathML sourceAgzn1+–SO was smaller than that of the AgZn1+AgZn1+. The stable p-type conduction of the ZnO:(Ag, S) was suggested to be attributed to the increase of the AgZn1+AgZn1+ content induced by S doping and to the formation of the AgZn1+–SOAgZn1+–SO complex acceptor.