Effect of SILAR cycle on gas sensing properties of In2O3 thin films for CO gas sensor

Abstract

In2O3 thin films were deposited via Successive Ionic Layer Adsorption and Reaction (SILAR) method on glass substrates at 20, 30, 40, and 50 SILAR cycles. The effect of SILAR cycle on the general and CO gas sensing properties of the films was investigated. The GIXRD and FE-SEM results indicated that the films had cubic phase and porous morphology. As a function of temperature and gas concentration, CO gas sensing measurements of In2O3 thin film-based sensors were made, and the detection limit and operating temperature values were determined. The optimal operating temperature was found to be 222 °C for all sensors. The CO sensing results demonstrated that the sensor with 30 SILAR cycle had higher sensitivity for 1–100-ppm gas concentration values at 222 °C operating temperature than the others. The sensing responses of the sensors increased from 12 to 29% for 1-ppm CO gas and from 52 to 91% for 100-ppm CO gas at 222 °C, depending on the SILAR cycle. The detection limit of the sensors toward CO gas at 222 °C reached 1 ppm, and the response and recovery times of the sensor with 30 SILAR cycle were found to be 54.2 s and 49 s for 1-ppm CO, and 47.4 and 62.5 s for 100-ppm CO gas at 222 °C, respectively. The activation energy (Ea) values of the sensors were found to change between 0.08 and 0.15 eV in the temperature range of 300–340 K and between 0.700 and 0.749 eV in the temperature range of 350–520 K, with SILAR cycle number. Finally, in this study, it was revealed that SILAR cycle number changed the structural, morphological, and CO gas sensing properties of the In2O3 thin films, and SILAR cycle optimization was performed for the highly sensitive In2O3 thin film-based CO gas sensor.