A Bifacial SnO2 Thin-Film Ethanol Gas Sensor

This letter produces a bifacial SnO ₂ thin-film ethanol gas sensor using micro-electromechanical systems technology. A 1-μm-thick SnO ₂ film (290 μm × 290 μm) is deposited as the lower sensing layer, and a square (625 μm × 625 μm) 2-μm SnO ₂ 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 SnO ₂ than a single-sided sensing layer, at an optimum working temperature of 200 °C.