Gate-Tunable Bilayer In ₂ Se ₃ –Based Room-Temperature Gas Sensor with Ultrahigh Sensitivity and Selectivity for NO, NO ₂ , and NH ₃

Development of highly sensitive and selective gas sensors is of paramount importance for environmental monitoring applications. In this work, we systematically investigate the electronic structure and charge transport properties of bilayer In₂Se₃ using density functional theory and nonequilibrium Green's function methods. First-principles calculations reveal that bilayer In₂Se₃ exhibits strong NH₃ adsorption with chemisorption characteristics at both the interlayer and bottom layer sites. Remarkably, the calculated recovery times for NO, NO₂, and NH₃ at the bottom layer are 3.75 × 10^-4, 2.33 × 10^-9, and 27.9 s, respectively, indicating rapid and complete recovery, which is crucial for the reusability of the sensor. The designed field-effect transistor gas sensor based on bilayer In₂Se₃ displays outstanding gate-tunable sensing characteristics in our simulations. At zero gate voltage, the device achieves remarkable sensitivities of 163% for NO₂ and 108% for NH₃ detection. Gate voltage modulation significantly enhances the sensing performance, with the response to NO increasing to 101% at a gate voltage of 2 V, a 2.6-fold improvement over the zero gate voltage. More importantly, the sensor demonstrates superior NO₂ selectivity at a gate voltage of 3 V, where its response substantially exceeds those for NO and NH₃. These findings validate bilayer In₂Se₃ for high-performance gas sensing and establish a new paradigm in designing environmental sensors with gate-voltage-tunable selectivity and ultrahigh sensitivity.