Ethylene Sensors Using Semiconducting Thin-Film and Palladium-Deposited Porous Alumina

Abstract

Ethylene sensors are developed using semiconducting thin-film and Pd-deposited porous alumina. The semiconducting thin-film is used as a sensing element, while porous alumina is used as a gas filtering element. The sensing film is double layered; SnO₂+V₂O₅(5mol%) or WO₃+TiO₂(10mol%) film is deposited as an upper layer on Fe₂O₃+TiO₂(5mol%)+MgO(4mol%) film as a lower layer. Pt+W(8wt.%) film is used as electrodes. All films are deposited on an alumina substrate by r.f. sputtering. Palladium film is also deposited on both sides of a porous alumina by r.f. sputtering, and it is used as catalyst that is effective for ethylene gas. The highest sensitivity to ethylene gas occurs at 275°C for the SnO₂-based sensor and at 250°C for the WO₃-based sensor. The SnO₂-based and WO₃-based sensors are selective to ethylene gas in temperature ranges from 240°C to 290°C and from 170°C to 350°C, respectively. Both sensors are sensitive to ethylene gas even at lower concentrations from 10ppm to 100ppm.