Experimental and theoretical studies of sputter deposited pure SnO₂ thin films for high selective and humidity-tolerant H₂ gas sensor

Hydrogen, owing to its clean and efficient combustion and abundance in the form of water, has emerged as an important energy source for future needs. For safety, it is essential to develop fast, selective and highly sensitive hydrogen detectors for any practical applications and the metal oxide-based chemiresistive gas sensors are the front-runners due to their compatibility with the electrical circuits and current semiconductor technology. This work presents excellent hydrogen sensing performance of magnetron-sputtered pure SnO₂ thin film-based sensors. The effect of deposition temperature on structure and hydrogen (H₂) gas-sensing properties of SnO₂ thin film is discussed. The maximum response 57.41% (500 ppm) is obtained at lower operating temperature of 200 °C for a sensor deposited at 125 °C. The response/recovery time of the sensor are found to be remarkably fast 50 s/39 s for 5 ppm concentration of hydrogen gas. The detection limit (DL) of the sensor as liner fit is 129.27 ppb. The stability and selectivity in humid conditions were also investigated and the sensor's response is found stable up to humidity of 40% RH. Sensor shows good selectivity toward H₂ gas in dry air and high humidity level 80% RH. The experimental results are explained and supported by simulation studies using the Crowell-Sze model in Finite-Difference Time-Domain (FDTD) simulations on the COMSOL Multiphysics platform. Drift Diffusion-Poisson equations were used to simulate the electric potential distribution in the active material during gas sensing. The significantly high sensing response, good selectivity and low operating temperature reported in this work, emphasize the strong potential of SnO₂-based thin film gas sensors for hydrogen detection.