Materials Transactions Online

Materials Transactions, Vol.46 No.08 (2005) pp.1942-1949
© 2005 The Japan Institute of Metals

Enhancing the Sensitivity of Oxygen Sensors through the Photocatalytic Effect of SnO2/TiO2 Film

Hsiao-Ching Lee and Weng-Sing Hwang

Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan

This paper investigates the effect of photocatalysis on the sensitivity of oxygen sensors constructed with SnO2/TiO2 thin films. An R.F. magnetron sputtering system is employed to fabricate SnO2/TiO2 double-layer films. The thin films are deposited with SnO2/TiO2 thickness ratios of 250/50, 200/100, 150/150, 100/200, and 50/250 nm, respectively. During deposition, the Ar:O2 flow rate is fixed at 4:1. To stabilize the material properties, the films are annealed for four hours at a temperature of either 550 or 650°C. The increase in sensitivity of the SnO2/TiO2 thin films when irradiated by UV light with a wavelength of 365 nm is investigated. The results indicate that the annealed samples have higher oxygen sensitivities than the as-deposited samples. The sensitivity of the non-annealed samples increases from 0.70 to 1.15 under UV irradiation, while the sensitivity of the annealed samples increases from 7.17 to 10.60. Therefore, it is clear that UV irradiation causes the sensitivity of the SnO2/TiO2 thin films to increase significantly. Finally, it is found that the oxygen sensitivity of the SnO2/TiO2 thin films increases as the SnO2/TiO2 ratio is reduced.

(Received 2005/4/14; Accepted 2005/7/11; Published 2005/8/15)

Keywords: photocatalytic effect, oxygen sensors, SnO2, TiO2, sensitivity

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