Gas sensing property of ZnO under visible light irradiation at room temperature

The photo-responded behavior of ZnO and its sensing response to ethylene or acetone under visible-light irradiation at room temperature were reported. A ZnO sensor without any response to target gas in the air atmosphere in dark at room temperature, exhibits not only a photo response but also an obvious sensing response to target gas in the air atmosphere under visible-light irradiation. It is suggested that the non-intrinsic photo-absorption induced by the native defects of ZnO (i.e., the two-photon or multi-photon excitation process via the intraband) may be responsible for the photo-responded behavior to the visible light. Moreover, a mechanism model that accounts for the solid-state process of photo-carrier generation/recombination is proposed to explain the photo-induced gas sensing response of ZnO under visible-light irradiation. This indicates that the photo-activated gas sensing response property of semi-conductor can be also caused by its non-intrinsic photo-absorption.