Theoretical description of gas/film interaction on SnO/sub x/

A simple depletion model based on the creation and destruction of Schottky oxygen vacancies near the gas-solid interface is shown to adequately account for the free carrier and mobility response of the SnO/sub x/ films reported by S.C. Chang and D.B. Hicks (1986). Expressions for the relationship between the surface potential, bulk carrier concentration and the reducing gas concentration are derived using the standard semiconductor electrostatic surface model and first order kinetic equations for gas/solid interactions. The results obtained indicate that thin-film gas sensors of the SnO/sub x/ variety behave more like a homogeneous system where free carriers dominate the response than as polycrystalline aggregates dominated by mobility variations arising from potential variations at the intergrain boundaries.<
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