Fast highly-sensitive room-temperature semiconductor gas sensor based on the nanoscale Pt–TiO2–Pt sandwich

• Published in: Sensors and actuators. B, Chemical Vol. 207; pp. 351 - 361
• Main Authors: Plecenik, T., Moško, M., Haidry, A.A., Ďurina, P., Truchlý, M., Grančič, B., Gregor, M., Roch, T., Satrapinskyy, L., Mošková, A., Mikula, M., Kúš, P., Plecenik, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2015
• Subjects: Electrodes; Gas sensor; Gas sensors; Grains; Hydrogen; Nanoscale; Nanostructure; Platinum; Room temperature; Sandwich; Semiconductors; Sensors; TiO2; Titanium dioxide; Nanoscale; Sandwich; Gas sensor; Hydrogen; Room temperature; TiO2
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2014.10.003

•Hydrogen gas sensor based on the nanoscale Pt–TiO2–Pt sandwich is presented.•The sensor exhibits high sensitivity and fast reaction time at room temperature.•The high sensitivity is due to the high applied field and small top electrode width.•The hot-electron-transport theory of the sensor response is developed. Development 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–TiO2–Pt sandwich. The sensor consists of a thin (∼30nm) nanocrystalline TiO2 layer with ∼10nm grains, placed between the bottom Pt electrode layer and top Pt electrode shaped as a long narrow (width w down to 80nm) stripe. If we decrease w to ∼100nm and below, the sensor exposed to air with 1% H2 exhibits the increase of response (Rair/RH2) up to ∼107 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 TiO2 layer, combined with onset of the hot-electron-temperature instability when the tiny grains are subjected to high electric field.