Structural and electrical properties of In2O3-SeO2 mixed oxide thin films for gas sensing applications

In2O3-SeO2 mixed oxide thin films have been obtained by thermal evaporation of a stoichiometric In-Se starting charge and subsequent thermal annealing in an oxygen flow. High-resolution transmission electron microscopy, small area electron diffraction, and digital image processing have been employed in order to investigate the structure and the morphology of the films obta ined. Hall effect and resistivity measurements in a vacuum and in a control led atmosphere have been performed to obtain information about physical pro perties of these films. The experimental data show evidence that the electr ical conductivity of these films undergoes a remarkable variation due to ex posure to small concentrations of NO in dry synthetic air or argon. To inte rpret the behavior of such films, an adsorption kinetic model has been deve loped and the conductivity variation as a function of gas concentrations, t ime, and temperature has been derived. The fitting of the theoretical and e xperimental behavior allows us to determine the adsorption kinetic paramete rs. (C) 2000 American Institute of Physics. [S0021-8979(00)09024-1].