Atomistic understanding of semiconductor gas sensors

Oxide semiconductors form a group of compounds whose specific properties of surfaces and interfaces are used for gas sensing. Our fundamental understa nding of the operation principles of these devices is still insufficient. T he abundance of phenomena on open oxide-semiconductor surfaces at elevated operation temperatures of the sensors is a central reason for the situation , in addition of the effects originating in the electrode-semiconductor con tacts. The exchange of lattice oxygen with the surrounding atmosphere and a possible diffusion of oxygen through oxygen-vacancy donors in n-type oxide s, especially at elevated temperatures, have also strong effects on the beh aviour of semiconductor gas sensors. Atomistic understanding of surfaces is the basis for the understanding of both the receptor and transducer functi ons of semiconductor gas sensors. The rutile structure tin dioxide, SnO2, t ogether with its most stable (110) face is the example material here. Espec ially, we consider the oxygen chemistry at the SnO2 (110) surface together with its connection to dipole layers and band-gap surface states. For examp le, the role of tin (II) ions at the reduced SnO2 (110) surface is discusse d. A "transistor model" is also given to describe the transducing propertie s of semiconductor gas sensors. (C) 2001 Elsevier Science Ltd. All rights r eserved.