Gas Sensing Properties of a Novel Indium Oxide Monolayer: A First-Principles Study.

We present a comprehensive first-principles investigation into the gas sensing capabilities of a novel two-dimensional (2D) Indium Oxide (In2O3) monolayer, using density functional theory (DFT) calculations. Targeting both resistive-type and work-function-based detection mechanisms, we evaluate the monolayer's interactions with ten hazardous species, namely NH3, NO, NO2, SO2, CS2, H2S, HCN, CCl2O, CH2O, and CO. To assess the sensor's deployability in ambient environments, we also analyze its interaction with common atmospheric or background gas molecules, such as, O2, CO2, and H2O. We note that NO and H2S molecules, with adsorption energy (E ads) of -0.68 and -1.29 eV respectively, can be detected via both substantial conductivity modulation (>106×) and work-function shifts (Δϕ = 38.27 and 21.70% respectively). NH3 and HCN molecules, with E ads = -1.07 and -0.46 eV respectively, on the other hand are readily detected through significant work-function alteration only (Δϕ = 25.38 and 17.80% respectively). Biaxial mechanical strain further proves highly effective in broadening the sensing capability, with tensile strain adjusting the adsorption energy favorably in most cases and additionaly facilitating the detection of NO2, CS2, CCl2O, and CO molecules through either conductivity modulation or work-function shifts. Compressive strain, on the contrary, facilitates detection of the CH2O molecule via work-function modulation. These results establish 2D In2O3 as a highly promising and tunable platform for next-generation miniaturized gas sensors suited for environmental monitoring and safety-critical applications.