Oxygen sensing with ZnO thin films

ZnO thin films for O 2 sensing were obtained with atomic layer deposition (ALD) and treated with rapid thermal annealing (RTA). The response of the ZnO conductivity to O 2 exposure is reversible at 270°C. The sensitivity and responsivity are increased in comparison with O 2 sensing at 500°C that was reported in literature. It is assumed that the improved O 2 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 O 2 sensing thus results in reduced power consumption while improving the O 2 sensing characteristics.