Sensitivity of metal oxide gas sensors to non-parabolic intergranular barriers

Abstract

We analyze the electrical conductivity of polycrystalline semiconductor solids due to the presence of Schottky-type potential barriers formed at intergrains. The density of charged dopants along the grains is usually considered constant leading to parabolic intergranular potential barriers. If temperature is high enough to allow sufficiently mobility to the dopants, their resulting equilibrium distribution is far from constant leading to potential barriers that show a strong non-parabolic character. Implications for the electrical conductivity and then on the sensitivity to barrier height and sample doping in metal oxide gas sensors are discussed.