Copper on-top-sputtering induced modification of tin dioxide thin film gassensors

Thin film gas sensors based on purr tin dioxide were modified by sputtering of copper on the surface of the films. A gradual increase of an amount of the on-top-Cu produced increasing doping with uniform distribution of coppe r throughout entire tin oxide film. An increase of an amount of Cu caused c ontinuous variation of the clean air resistance and the resistance response to CO and H-2 gases at various temperatures (290-550 K). For certain Cu am ounts, samples shaw a large sensitivity towards one gas component while the cross-sensitivity remains small. The Cu-effect is discussed considering th e variation of the Fermi level induced by doping and the clusters of topper on the surfaces of the grains. (C) 1999 Elsevier Science S.A. All rights r eserved.