Enhancement of conductivity and transmittance of ZnO films by post hydrogen plasma treatment

We studied the effects of hydrogen plasma treatment on the electrical and optical properties of ZnO films deposited by radio frequency magnetron sputtering. It is found that the ZnO:H film is highly transparent with the average transmittance of 92% in the visible range. Both carrier concentration and mobility are increased after hydrogen plasma treatment, correspondingly, the resistivity of the ZnO:H films achieves the order of 10−3 Ω cm. We suggest that the incorporated hydrogen not only passivates most of the defects and/or acceptors present, but also introduces shallow donor states such as the VO-H complex and the interstitial hydrogen Hi. Moreover, the annealing data indicate that Hi is unstable in ZnO, while the VO-H complex remains stable on the whole at 400 °C, and the latter diffuses out when the annealing temperature increases to 500 °C. These results make ZnO:H more attractive for future applications as transparent conducting electrodes.