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

Abstract

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 (<i>E</i> _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 <i>E</i> _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.