Tunable gas sensing features of Janus In₂STe monolayers: insights from first-principles and multiphysics studies on...

The detection of hazardous gases plays a critical role in both industrial and healthcare applications. MOS (metal oxide semiconductor) sensors have been extensively studied in gas sensing applications, but they have low selectivity, require higher working temperatures, and use a lot of power. This work investigates the sensing and adsorption properties of hazardous gases (NH₃, SO₂, H₂S, NO₂, HCN, and CO₂) on a Janus In2STe monolayer using first-principles density functional theory (DFT) calculations and COMSOL Multiphysics modeling. First-principles analyses reveal that SO₂ is chemisorbed on In₂STe, while the other gases are physisorbed. Among all the adsorbed gases, SO₂ exhibits the highest adsorption energy (-0.82 eV), which suggests the strongest interaction with the Janus In₂STe monolayer. The sensor based on this monolayer shows a remarkable chemiresistive sensitivity (93.28 × 10⁶%) and a suitable recovery time (74 seconds) for SO₂, significantly outperforming other gases. Additionally, a sensor incorporating the Janus In₂STe monolayer as the sensing layer was simulated using COMSOL to validate these findings further. At room temperature (RT), Janus In₂STe showed a high response (R _a/R _g) of 17.62 to 50 ppm of SO₂, an impressive sensitivity of 0.308 ppm^-1, and excellent selectivity for SO₂ in mixed gas environments, surpassing conventional gas sensors. These results offer valuable insights for the manufacture of low-power-consuming and selective gas sensors and emphasize their potential for predictive modeling in guiding sensor design before synthesis.