Fast highly-sensitive room-temperature semiconductor gas sensor based on the nanoscale Pt-TiO 2 -Pt sandwich, Sensors and Actuators B: Chemical (2014), http://dx. AbstractDevelopment of fast highly-sensitive semiconductor gas sensors operating at room temperature, which would be compatible with semiconductor technology, remains a challenge for researchers.Here we present such sensor based on a nanoscale Pt-TiO 2 -Pt sandwich. The sensor consists of a thin (~30 nm) nanocrystalline TiO 2 layer with ~10 nm grains, placed between the bottom Pt electrode layer and top Pt electrode shaped as a long narrow (width w down to 80 nm) stripe. If we decrease w to ~100 nm and below, the sensor exposed to air with 1% H 2 exhibits the increase of response (R air / ) up to ~ 10 7 and decrease of the reaction time to only a few seconds even at room temperature. The sensitivity increase is due to a nontrivial non-ohmic effect, a sudden decrease (by three orders of magnitude) of the electrical resistance with decreasing w for w ~ 100nm. This non-ohmic effect is explained as a consequence of two nanoscale-related effects: the hydrogen-diffusion-controlled spatially-inhomogeneous resistivity of the TiO 2 layer, combinedPage 2 of 41 A c c e p t e d M a n u s c r i p t 2 with onset of the hot-electron-temperature instability when the tiny grains are subjected to high electric field.

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Abstract:Titanium dioxide thin films are extensively studied for applications in solid state gas sensor devices. Their gas sensing properties are strongly dependent on deposition technique, annealing temperature, film thickness and consequent properties like crystalline structure, grain size or amount of defects and impurities. In this work we report the gas sensing properties of TiO 2 thin films prepared by reactive magnetron sputtering technique and subsequently annealed at temperatures 600°C and 900°C. The films were exposed to different concentrations of H 2 gas up to 10 000 ppm. Their sensitivity to gas at various operating temperatures, ranging from 250°C to 450°C, was obtained by measuring their resistance. 07.07.Df, 68.47.Gh, 73.25.+i, 82.47 PACS (2008):

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