Enhanced photoresponse of epitaxially grown ZnO by MoO₃ surface functionalization

ZnO has broad applications in optoelectronic devices, including ultraviolet light emitters and photodetectors. Herein we report the impact of MoO₃ surface functionalization on the photoresponse of epitaxially grown ZnO. Under illumination with 350 nm UV light, the photocurrent of ZnO is found to be enhanced by 2.87 times after the deposition of 0.2 nm MoO₃. As corroborated by in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy results, the enhanced photoresponse derives from MoO₃ related gap states within the band gap of ZnO and larger upward band bending at the interface, which is attributed to the strong electron transfer from ZnO to MoO₃. Moreover, photoluminescence results reveal that the recombination probability of the photo-generated charge carriers in ZnO is reduced after MoO₃ surface functionalization.