Improving ethanol sensing characteristics of indium oxide thin films by nitrogen incorporation

Abstract

Incorporation of suitable dopants in semiconducting metal oxide (SMO) based gas sensors have been one proficient approach employed to improve their sensing characteristics. Indium oxide (In2O3), which is a n-type SMO, has been widely investigated for its ethanol sensing characteristics. For doping of In2O3, typically various metal based dopants have been considered, whereas non-metallic dopants have drawn only limited attention. In this work we have examined the impact of nitrogen incorporation on the ethanol sensing properties of In2O3 thin film. Using urea as a source, nitrogen has been doped at the interstitial site of In2O3 synthesised using sol-gel technique. Ethanol sensing properties of the nitrogen doped In2O3 thin film has been compared with pure In2O3 sensor over a wide range of temperature. Doping of nitrogen has been found to significantly enhance the ethanol sensing response of In2O3 (99.7 % at 250 °C), improves the stability of response under humid condition (change of response ∼ 4.5 % within relative humidity range 10–80 %) and offers very fast response time (1 s for 300 ppm ethanol). We discuss that modification of the electronic properties of In2O3 due to interstitial nitrogen incorporation leads to its superior sensing properties on exposure to ethanol vapour.