Tuning lattice defects and photocurrent response of ZnO thin films by Mg doping and Ar-H2 atmospheric plasma treatment

Abstract

The effects of Mg doping and Ar-H2 atmospheric pressure plasma jet (APPJ) treatment on zinc oxide (ZnO) thin films were investigated. Mg doping has been demonstrated to facilitate the incorporation of atomic hydrogen in the ZnO lattice via Ar-H2 APPJ. The co-doping of Mg and H changed ZnO’s primary oxygen defect type from vacancy (VO) to interstitial (Oi), which reduced photocorrosion significantly. The dominance of interstitial defects (i.e., Zni and Oi) in the H-doped Zn0.9Mg0.1O thin film was confirmed by photoluminescence spectroscopy. Zni shallow donors improved light absorption at wavelengths > 650 nm, increasing the film’s photocurrent density. Without Mg, doping H via Ar-H2 APPJ was ineffective for pure ZnO thin film. The dominance of VO in pure ZnO thin film after APPJ, though enhanced light absorbance, gave rise to an erratic photocurrent response due to the instability of VO. The lack of acceptor states also led to severe photocorrosion.