Effect of doping behaviors of Ag and S on the formation of p-type Ag–S co-doped ZnO film by a modified hydrothermal method

Publication date: 1 February 2016
Source:Thin Solid Films, Volume 600
Author(s): Shiwang Long, Yongfeng Li, Bin Yao, Zhanhui Ding, Ying Xu, Gang Yang, Rui Deng, Zhenyu Xiao, Dongxu Zhao, Zhenzhong Zhang, Ligong Zhang, Haifeng Zhao
Reproducible p-type Ag–S co-doped ZnO (ASZO) films were grown on glass substrate by a modified hydrothermal method, where reaction solution is separated from alkali solution and O2 is removed from autoclave to avoid deoxidation of Ag⁺ and oxidation of S²⁻ in the solution. It is found that the Ag substitutes for the Zn in monovalent state (AgZn ⁺) and the S for the O in bivalent state (SO ²⁻) in the ASZO. Both AgZn ⁺ and SO ²⁻ have two doping states, each AgZn ⁺ is surrounded by 4O²⁻ to form AgZn ⁺ acceptor and each SO ²⁻ is surrounded by 4Zn ²⁺, while AgZn ⁺ bounds with nSO ²⁻ to form AgZn ⁺–nSO ²⁻(n≤4) complex acceptor. It is demonstrated that Ag doping can suppress the formation of interstitial Zn and O vacancies in the ASZO and S doping can enhance solubility of Ag in the ASZO. Hall measurement indicates that the p-type ASZO film has a hole density as high as 10¹⁸ cm⁻³, which is much higher than that of ASZO prepared by magnetron sputtering. The mechanism of the formation of the p-type ASZO with high hole density is suggested in the present paper.