Abstract
To verify theoretical model based on the surface depletion effect of oxide semiconductor in small crystallite, the SnO2 particles of different crystallite size and donor density were prepared by controlling heat-treatment temperature and Fe3+ doping concentration, respectively. In addition, Fe3+-doped SnO2 was compared with Fe2O3-loaded SnO2 to discuss the effect of donor density. The electrical resistance and sensor response of prepared SnO2 films were measured in various partial pressures of oxygen and hydrogen. As results, both undoped- and Fe3+-doped SnO2 showed the volume depletion in the oxygen concentration of more than 2.5% at 350°C. The dependence of electrical resistance on oxygen partial pressure for smaller crystallite had steeper slope. Furthermore Fe3+-doping improved the sensor response to hydrogen, while the Fe2O3-loading did not work. Good agreement between experimental data the volume depletion theory was found.
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