Bandgap Narrowing of Zinc Oxide (ZnO) by Nitrogen Incorporation for Solar Driven Hydrogen Production

In this study, report on the synthesis of ZnO:N thin films by reactive RF magnetron sputtering using a Zn metal target & ZnO target in mixed N-2 and O-2 ambient. We found that the N concentration in ZnO:N thin films can be effectively controlled by varying the RF power. ZnO:N films with narrowed bandgaps were synthesized. The photoelectrochemical properties of nitrogen-incorporated ZnO (ZnO:N) films were measured and compared with those of pure ZnO films. We find that nitrogen incorporation narrows the bandgap of ZnO and shifts the optical absorption into the visible-light regions. We further find that the ZnO:N films provide considerable photoresponse in the long-wavelength regions. As a result, the ZnO:N films exhibit higher photocurrents than pure ZnO films.