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.