Optical CO gas sensor using a cobalt oxide thin film prepared by pulsed laser deposition under various argon pressures.

An optical CO gas sensor was investigated using cobalt oxide thin films prepared by pulsed laser deposition. The cobalt oxide films were deposited on quartz glass and silicon wafer substrates in Ar at 0.07-133 Pa. The morphology and crystal phase of the films were changed by Ar pressure. Sensitivity was estimated as the transmittance change of the film in dry air and at 200 ppm of CO gas ambient at 350 degrees C. The morphology of the films greatly affected the sensing properties. The optimum Ar pressure for cobalt oxide film preparation for CO gas sensing was suggested to be 13.3 Pa, based on the relationship between the morphology and the optical sensor properties of the films.