Effect of gas type, pressure and temperature on the electrical characteristics of Al-doped SnO2 thin films deposited by RGTO method for gas sensor application

Abstract

In this paper, we present the experimental results of Al-doped SnO2 thin films obtained by Rheotaxial Growth and Thermal Oxidation (RGTO) method. The effect of gas type (synthetic air, CO, NO2 and H2), pressure (10−4, 1 and 100 mbar) and temperature (in the range 300–650 K), on the electrical properties of Al-doped SnO2 thin films were considered. The change of the work function of Al-doped SnO2 thin films as a function of exposure time to synthetic air, CO (150 ppm), H2 (1000 ppm) and NO2 (80 ppm) was discussed under different pressures of 10−4, 1 and 100 mbar. The effect of ambient temperature at 303,373 and 433 K on the work function difference was investigated. The results reveal that the sensitivity of reaction to the gases was improved to high ambient temperature. The time and temperature dependent of electrical properties of the Al-doped SnO2 films were studied using four probe method. The Al-doped SnO2 films demonstrate negative temperature coefficient (NTC) characteristics of resistance in the higher temperature range as well as positive temperature coefficient (PTC) characteristics of resistance in the lower temperature range. The best sensitivity and the optimum work temperature were also considered.