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Published online by Cambridge University Press: 01 February 2011
TiO2 anatase thin films with different thickness (100 – 1200 nm) have been deposited on glass, sapphire and Si(100) substrates using pulsed DC magnetron reactive sputtering. The thin films were exposed to carbon monoxide (CO) gas at different concentrations (20–100 ppm) in a nitrogen carrier, and the resistance was measured as a function of the CO concentration for films of different thicknesses for temperatures in the range of (100 - 300°C). The films with good crystalline order showed better response than amorphous films. The response increased monotonically with CO concentration. The thicker films showed higher sensitivity. The anatase films deposited on sapphire generally had a larger response than those deposited on glass or on silicon. The films on sapphire substrate showed good response at temperatures as high as 300°C, while those deposited on glass and silicon had good responses only to 200°C. Furthermore, the addition of different concentrations of O2 and H2 affected the response as expected. The response to CO in the presence of N2 showed good reversibility which is evidence that complete regeneration on turn off the CO does not require exposure to oxygen or air. The response and the recovery times are fast.