Hall measurement studies and an electrical conduction model of tin oxide ultrafine particle films

The Hall effect has been measured for ultrafine particle films of tin oxide (particle size 50–200 Å) in contact with reducing gases. Both the carrier concentration and mobility increased with an increasing concentration of reducing gas. As a result, conductivity, the product of the carrier concentration and mobility, shows a large gas concentration dependence. This means the ultrafine particle films are highly sensitive to gases. The variation of the carrier mobility with the gas concentration is interpreted in terms of a model in which the width of a long, thin channel, determined by particle size and Debye length, increases with a decrease in the number of O− ions desorbed by a chemical reaction with the reducing gases.