Surface Work Function of Transparent Conductive ZnO Films

The influence of Al doped on work function of ZnO thin film with C-axis preferred orientation were analyzed both theoretically and experimentally. Pure ZnO and Al-doped ZnO(ZnO:Al) films were deposited on n-type Si substrate by radio frequency (RF) magnetron sputtering. Surface work function were calculated using the first-principles with pseudopotential method based on density-functional theory (DFT) of ZnO and ZnO:Al surface structure. It was found that the theoretical value of work function of (002) plane ZnO and ZnO:Al were 5.076ev and 4.978ev respectively. Following I-V-T characteristics of the heterojunctions were investigated, the work function of ZnO and ZnO:Al were obtained at 4.71ev and 4.62ev, respectively. Al doped led to the value of work function reduced by 0.09ev, which was consistent with 0.098ev calculated by the first-principle algorithm.