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Density-controllable growth of SnO2 nanowire junction-bridging across electrode for low-temperature NO2 gas detection

Le, Dang Thi Thanh, Van Duy, Nguyen, Tan, Ha Minh, Trung, Do Dang, Trung, Nguyen Ngoc, Van, Phung Thi Hong, Hoa, Nguyen Duc, Van Hieu, Nguyen
Journal of materials science 2013 v.48 no.20 pp. 7253-7259
electrodes, ethanol, evaporation, hydrogen sulfide, nanowires, nitrogen dioxide, spatial distribution, temperature
The junction-bridging structure of metal oxide nanowires (NWs) improves gas-sensing properties. In this study, an on-chip growth method was used to fabricate gas sensors, it easily and effectively controls NW junctions. SnO₂NWs were synthesized by thermal evaporation at 800 °C with tin powder as the source. The density of the NW junctions was controlled by changing the mass of the source material. A source material with large mass yielded high-density NW junctions. With electrode spacing of 20 μm, NW junctions were formed from the source material of larger than 2 mg. Gas sensing results revealed that the junction sensors exhibited a good response to NO₂gas at a concentration of 1–10 ppm. The sensors exhibited a good response to NO₂gas at low temperature of up to 100 °C and short response–recovery time (~20 s). The sensors also had good selectivity to NO₂gas. The response (Rgₐₛ/Rₐᵢᵣ) to 1 ppm NO₂was as high as 22 at 100 °C, whereas the cross gas responses (Rₐᵢᵣ/Rgₐₛ) to 10 ppm CO, 10 ppm H₂S, 100 ppm C₂H₅OH, and 100 ppm NH₃were negligible (1.1–1.3).