Metal-oxide thin films are used as solid-state gas sensors for detection of various gases. With increased attention on use of hydrogen gas in various applications, fabrication of stable sensors with high sensitivity for hydrogen gas is particularly important.
In this article, the effect of several impurities on enhancement of sensitivity of indium oxide and tin oxide thin-film gas sensors to 2000 ppm hydrogen gas is investigated. Indium oxide films were prepared by thermal evaporation technique; and tin oxide samples were deposited by spray hydrolysis method. The effect of antimony, selenium, nickel, chromium, silver, zinc, copper, indium, and cadmium dopants on sensitivity of these films was studied. In all cases, sensitivity of a doped sample was compared with sensitivity of an undoped film located on the same substrate.
Nickel impurity produced the highest sensitivity increase in indium oxide films; while indium dopant resulted in highest sensitivity increase in tin oxide films. The comparative results showed that the evaporated samples were generally more sensitive to hydrogen gas; while, the sprayed samples had a lower drift and higher stability in the long run.
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