A.c. measurements on tin oxide sensors to improve selectivities and sensitivities

Abstract In the experimental section of this paper different d.c. and a.c. setups are described to measure and characterize the conduction properties in SnO 2 as a typical semiconducting oxide gas sensor. The use of different contact arrangements and monitoring at different frequencies make it possible to discriminate between different contributions to the overall conduction in SnO 2 . These include electronic contributions from contacts, surfaces, grain boundaries and the bulk as well as ionic contributions from adsorbed gas species. The electrical characterization makes it possible to describe them by means of a band scheme and equivalent circuits. Finally, specific results are reported to monitor CO, NO 2 and H 2 . These illustrate that the selectivity and sensitivity to monitor different gases can be improved significantly in frequency-dependent measurements.