Annealing time effect on the gas sensing properties of nano-crystalline SnO2 thin films prepared Physical Evaporation

In this work, annealing time effects on the gas sensing properties of nanocrystalline SnO2 thin films have been investigated. . Pure SnO2 thin films, with the thickness of 300 nm, have been grown using vacuum evaporation method on glass substrate. In order to be used as gas sensors, the samples were annealed at 400 ºC. Optimal annealing time was assessed by using different time periods (1, 2, 3 and 4h) for thin films annealing process. After these treatments, the electrical properties of sensors to ethanol have been studied. The results showed that the films annealed at 2 hours have the highest sensitivity, lower response time. In addition, it was shown that longer annealing time will result in the decrease of sensitivity, response rate and the increase of response time. The surface morphology of SnO2 films was characterized by a Scanning Electron Microscope (SEM). The grain size is 10, 16, 23 and 30 nm, respectively.