A Bifacial SnO2 Thin-Film Ethanol Gas Sensor

Abstract

This letter produces a bifacial SnO2 thin-film ethanol gas sensor using micro-electro mechanical systems technology. A 1- $\mu \text{m}$ -thick SnO2 film (290 $\mu \text{m}\, \,\times \,\,290\,\,\mu \text{m}$ ) is deposited as the lower sensing layer, and a square (625 $\mu \text{m}\,\,\,\,\times \,\, 625\,\,\mu \text{m}$ ) 2- $\mu \text{m}$ SnO2 is deposited as the upper sensing layer. For the interdigital transducer electrode and micro-heater, Cr is deposited at a thickness of 50-nm-thick Cr and Ni is deposited at a thickness of 250 nm. The measurement results show that with respect to the ethanol sensitivity, the bifacial structure has a much better ability to sense SnO2 than a single-sided sensing layer, at an optimum working temperature of 200 °C.