Thickness-dependent dual-mode NO₂ gas and EGFET pH sensing of two-dimensional SnS₂ thin films

This study investigates the layer-dependent material properties and dual-mode sensing performance of 2D tin disulfide ( S n S 2 ) thin films. High-quality S n S 2 films with controlled thicknesses (1–5 layers to 5 nm bulk) were synthesized via RF magnetron sputtering of an S n O precursor followed by CVD sulfurization. Comprehensive characterizations (Raman, XRD, XPS, and HRTEM) confirmed stoichiometric, highly crystalline layered structures with an interlayer spacing of 0.59 nm. Electrical evaluations revealed strong layer-dependent gas and electrochemical sensing. Crucially, the 3-layer S n S 2 device (~2 nm) exhibited optimal sensitivity and linearity for both N O 2 gas and EGFET pH sensing. This enhancement is attributed to the matching between the physical channel thickness and the Debye screening length, which maximizes full-channel electrostatic modulation while eliminating bulk shunting paths. These findings highlight thickness engineering as a promising path for 2D multifunctional nanoelectronics.