engleski

Nano-sized semiconductor gas sensors

Nano-Sized Semiconductor Gas Sensors Božidar Etlinger “Rudjer Bošković” Institute, Zagreb Some semiconductive metal oxides (SnO2, TiO2, In2O3, ZnO, WO3) were sensitive to the gas compositions of surrounding atmosphere. Nanosized powders of those semiconductor metal oxides were used to improve the available gas sensors´ performance to allow their application in environmental monitoring. Semiconductor sensors detect gases via variations in their resistances. The negatively charged oxygen (as O2-, O- and O2-) adsorbates and to cover the surface of sensors builds a space-charge region on the surface of the metal-oxide grain and the resistance of an n-type semiconductor gas sensor in air is high due to the development of the potential boundary. When the sensor is exposed to an atmosphere containing inflammable gases (as H2, CH4, NOx, NH3...) at high temperatures (more than 120 oC), a lower steady-state surface coverage of the adsorbates is established and decrease the potential barrier height and resistance dropped. The sensitivity some semiconductor metal oxides are discussed in the dependence on concentration of hazard gases, doping of noble metal, effects of grain size, sensor configuration and operating temperatures. Some new challenges are suggested too.

gas sensor; nanosized powder

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