Abstract

The effect of gap size on the gas sensitivity of semiconductor gas sensor was evaluated in the NO2 sensing using WO3 nanosensor, the Cl2 sensing using In2O3 nanosensor and the H2S sensing using SnO2 nanosensor. The nano-gap effect was markedly observed in the NO2-WO3 system and the Cl2-In2O3 system (resistance increase), while the H2S-SnO2 system showed the weak nano-gap effect. This difference resulted from the ratio (Si/Sgb) of sensitivity at semiconductor oxide-electrode interface (Si) to at grain boundary (Sgb). The NO2-WO3 and the Cl2-In2O3 systems showed the large Si/Sgb ratio (32-43), while the small ratio (9.7) was obtained in the H2S-SnO2 system at the gas concentration of 0.5-1 ppm. It was found that the clearer nano-gap effect was obtained for the system having the larger Si/Sgb ratio. In the system having large Si/Sgb ratio, the nano-design of electrode structure like nano-gap electrode was important for high sensitivity gas sensors.

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