Fast-responding ethanol sensor with extremely low detection limit: Influence of Pt film thickness on gas sensing properties

Abstract

To facilitate alcohol detection in exhaled breath, high-performance gas sensors capable of rapidly responding to low-concentration target gases in highly humid environments are required. In this study, we developed In₂O₃ nanorods (NRs) decorated with Pt nanoparticles (NPs) to improve selective C₂H₅OH detection under dry and 80 % relative humidity (RH) conditions. Using glancing angle deposition (GLAD), we fabricated In₂O₃ NRs with Pt film of varying film thicknesses (0.5, 1, and 2 nm), which transformed to NPs after the subsequent annealing process, to systematically identify the optimal Pt NPs size and distribution. Optimized In₂O₃ NRs with an initial Pt thickness of 1 nm exhibited the highest ethanol response at 450 °C, with a theoretical detection limit (DL) calculated to be 0.42 parts per billion (ppb) in dry air and 6.1 ppb under 80 % RH. This enhanced performance is attributed to the expansion of the electron depletion layer (EDL) due to Schottky barrier formation at the Pt- In₂O₃ interface, alongside a spillover effect that enhances gas adsorption and reaction on the In₂O₃ surface, where Pt NPs contribute both electronic and chemical sensitization effects. These findings indicate that In₂O₃ NRs with Pt NPs are promising candidates for next-generation ignition interlock devices (IIDs), offering high selectivity, rapid response times, and stability in high-humidity environments.