Tuning the structural and NO2 gas sensing properties of SnO2 films via In doping

Abstract

This study investigates the improvement of chemiresistive gas sensor properties in SnO₂ thin films by In doping via scalable spray pyrolysis. By systematically varying the indium concentration from 0 to 7.5 at.%, we found that a doping level of 5 at.% optimally maintains crystal integrity while significantly improving the sensor performance for nitrogen dioxide (NO₂), a common environmental pollutant. The In-doped sensors achieved a peak sensitivity of 109 at an operating temperature of 200 °C, with a rapid response time of 8 s and a recovery time of 70 s, outperforming the undoped sensors. Structural analysis showed that a 5 at.% doping reduced the grain size from 93 nm to 73 nm, which increased the surface area and improved the dynamics of gas adsorption. In addition, a reduction in surface roughness and a change in the texture coefficient T₍₁₁₀₎ were observed, indicating that the surfaces have become smoother, and the crystal growth orientations have changed, leading to an improvement in electron transport. Doping with In significantly improves the electronic structure and surface reactivity of SnO₂ films. This method enables the production of highly effective NO₂ sensors, which are important for air quality monitoring and environmental protection.