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

• Fabrication of uniform, scalable In 2 O 3 nanorods decorated with Pt nanoparticles via glancing angle deposition (GLAD). • Optimizing Pt NP size and distribution for ethanol sensing by tuning In 2 O 3 NR form factors and Pt NP thickness ~2 nm. • Demonstrating ethanol detection limits of 0.42 ppb (dry air) and 6.1 ppb (80% RH at 450 °C) with mechanism studies. 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 In 2 O 3 nanorods (NRs) decorated with Pt nanoparticles (NPs) to improve selective C 2 H 5 OH detection under dry and 80 % relative humidity (RH) conditions. Using glancing angle deposition (GLAD), we fabricated In 2 O 3 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 In 2 O 3 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- In 2 O 3 interface, alongside a spillover effect that enhances gas adsorption and reaction on the In 2 O 3 surface, where Pt NPs contribute both electronic and chemical sensitization effects. These findings indicate that In 2 O 3 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.