Sensing Mechanism and Behavior of Sputtered ZnCdO Ozone Sensors Enhanced by Photons for Room- Temperature Operation

ZnCdO oxide thin films have been deposited by using the radiofrequency cosputtering method to prepare ozone sensors for room-temperature operation. The sensors were fabricated in the order: electrode/sensor/glass/illuminant. The mechanisms of photo-assisted oxidation and reduction on the surface of the ZnCdO ozone sensors were investigated. Free electrons and holes were generated by exposure of the surface of the ZnCdO ozone sensor to ultraviolet light, tending to enhance surface absorption of dissociated O-2 molecules and dissociation of adsorbed oxygen ions, respectively. Thereby, the sensitivity of the ZnCdO ozone sensor was increased. This photon exposure method can replace the conventional heating mode used in ozone sensors. Moreover, 405-nm light from a light-emitting diode, corresponding to photon energy of 3.061 eV, was found to assist the processes of oxidation and reduction due to the chemical reaction of the ozone gas. We present a possible route for fabrication of portable ZnCdO ozone sensors for room-temperature operation.