DFT-Informed Work-Function Model Coupled with Polarized TFET for Gas Sensing via Mole Fraction-Controlled Tunneling

Density functional theory (DFT) is employed to quantify the adsorption energy and work-function variation (Δϕ) for representative gas-metal systems: H2/Pd(111), O2/Ag(111), H2O/Pt(001), and CO/Rh(111) under both molecular and dissociative adsorption modes. A Langmuir-based thermodynamic model translates these microscopic work-function shifts into temperature- and pressure-dependent surface potentials by incorporating equilibrium surface coverage (θ). The resulting modulation is integrated into a polarized tunneling field-effect transistor (TFET) framework using the Wentzel–Kramers–Brillouin (WKB) formalism, accounting for strain coherence and relaxation to enhance structural reliability for sensor arrays. The threshold voltage response is analyzed to correlate microscopic adsorption phenomena with macroscopic device characteristics. The integrated DFT-TFET approach reveals stronger modulation under dissociative adsorption and stable tunneling under optimized polarization coupling, establishing a predictive foundation for highly sensitive, wide dynamic range, and fabrication-tolerant TFET-based gas sensors for next-generation integrated nanotechnology applications.