Evaluation of Depletion Layer Width in Antimony-Doped Tin Oxide Thin Films for Gas Sensors

Abstract

The sensing properties of semiconductive gas sensors originate from the resistance variation of depletion layer in each grain of the element. One of the most fundamental factors in this type of sensors is the width of depletion region. In this work, the antimony-doped tin oxide thin films for gas sensors are prepared via sol-gel routes on alumina substrates. The influence of antimony addition amount on electrical resistance of thin films is concluded. The relationship is plotted in the coordinates of logarithmic resistance against doping amount. On the basis of Schottky barrier model, a novel method is proposed to evaluate the width of depletion layer of semiconductive gas sensors by using the first order derivative of logarithmic resistance with respect to doping amount. Thus, the depletion layer width of the prepared antimony-doped thin film is calculated and its influencing factor is also discussed.