Oxygen sensing with ZnO thin films

ZnO thin films for O₂ sensing were obtained with atomic layer deposition (ALD) and treated with rapid thermal annealing (RTA). The response of the ZnO conductivity to O₂ exposure is reversible at 270°C. The sensitivity and responsivity are increased in comparison with O₂ sensing at 500°C that was reported in literature. It is assumed that the improved O₂ sensing characteristics are due to the increased surface-to-volume ratio of the film. The responsivity that is defined as the inverse of response time also improved because of the decreased bulk diffusion length. The application of ZnO thin films that are obtained by ALD to O₂ sensing thus results in reduced power consumption while improving the O₂ sensing characteristics.