Rf magnetron sputtering system were using to deposited ZnO thin films onto corning substrates as a CO gas sensor. The sensing
properties of the thin film
thickness on CO gas was investigated. The film thickness was waried by controlling the deposition time.The CO gas sensing
properties were determined by in situ measurement for surface resistance of the thin film as a function of film thickness, operating temperature and various CO concentrations. The gas sensitivity of ZnO gas sensor depends upon its grain size.