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- One more field of scientific interests of the group is investigation of resistivity gas
sensors based on the tin dioxide. This research is developed in a cooperation with the
scientific group headed by Prof. A.M.Gas'kov (Chemistry Department of Moscow State University).
A gas sensor is a structure which consists of a substrate, an insulating layer, a
polycrystalline tin dioxide film and contacts. Each element of the structure may
contribute into the conductivity process and influence gas sensor parameters. Besides that
resistance of the sensitive element - SnO2 film - depends on grain size and
barrier height at grain boundaries, film thickness, surface states, doping elements etc.
So the problem of a definition of a mechanism of gas sensitivity and a sensor selectivity
appears to be rather complicated. Usually properties of such structures are investigated
at elevated temperatures. We apply a low temperature technique to determine the
contribution of different of factors into the conductivity process, to optimize parameters
of a sensor and to choose a mostly preferable operating regime. Low temperature
measurements of resistance, current-voltage characteristics and capacitance appeared to be
especially efficient for the study of high-resistivity SnO2 films doped with Cu
and Ni. Relaxation processes after exposition of the SnO2(Cu) films to hydrogen
sulfide are found to be of long duration and the unequilbrium state of the structure is
frozen at cooling. So one can observe the change of the low temperature conductivity
character at various ranges of exposition of the structure in H2S atmosphere.
These data give an important information to clarify the mechanism of a sensor sensitivity.
- Relative key references
- 1. B.A.Akimov, A.V.Albul, A.M.Gas'kov, V.Yu.Il'in, M.N.Rumyantseva, L.I.Ryabova and
M.Labeau. The electrical conductivity of polycrystalline SnO2(Cu) films and
their sensitivity to hydrogen sulfide, Semiconductors 31, 335 (1997).
- 2. M.N.Rumyantseva, A.M.Gaskov, L.I.Ryabova, J.P.Senateur, B.Chenevier, M.Labeau.
Pyrosol spraying deposition of copper- and nickel-doped tin oxide films, Materials Science
and Engineering B41, 333 (1996).
Contact person: Ludmila Ryabova
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