Individual and collective effects of oxygen and ethanol on the conductance of SnO2 thin films

We study the changes in the conductance of the fully depleted SnO2 films exposed both to oxygen or ethanol vapors in vacuum and to their mixture in the air. The dependence of free carrier concentration on the acceptor-like and/or donor-like gas pressure is discussed assuming the flat-band condition. We show that the gas sensitivity of the depleted semiconductor layer can be explained taking into account the compensation of the sample conductivity by the surface adsorbed species. The results of calculations are in good agreement with our experimental data. (C) 2000 American Institute of Physics. [S0003-6951(00)03617-2].