Pulsed laser deposited ZnO films and their humidity sensing behavior

The present paper describes an opto-electronic humidity sensor based on thin film of zinc oxide prepared by pulsed laser deposition method. Being optical in nature it gives electromagnetic disturbance-free monitoring. The sensing element is a right-angled isosceles prism with its base coated with ZnO thin film. Films have been characterized by XRD, SEM, and optical transmission. Film grown with substrate at room temperature is amorphous whereas that grown at elevated temperature is single crystalline with grain size 38.52 nm. Film deposited at room temperature is sensitive to humidity over a wide range i.e. 5–90RH% while that deposited at elevated temperature is found to be insensitive to humidity. The sensor shows better sensitivity for higher range of humidity. The response and recovery time of the sensor element have also been evaluated. This sensor configuration can be used for on-line applications and in-situ monitoring.