EFFECT OF MICRO-GAP ELECTRODE IN NITROGEN DIOXIDE SENSOR USING TUNGSTEN OXIDE THIN FILM

摘要

The micro-gap electrode with various gap sizes (0.2-1.6 μm) and various line width (10-50 μm) have been fabricated by means of MEMS techniques (photolithography and FIB techniques). The WO_3 thin film was deposited on the micro-gap electrode by using suspension dropping method to be micro-gas-sensor. The sensing properties to dilute NO_2 of WO_3 thin film microsensors were measured in the range of 0.05-0.5 ppm at 200℃ and the effects of micro-gap size and line width on dilute NO_2 sensing properties were investigated. The sensitivity to dilute NO_2 was almost unchanged for the gap size larger than 0.85 μm. However, the sensitivity tended to increase with decreasing gap size less than 0.85 μm. Concerning the line width effect, the sensitivities were higher for the sensor with 50 μm width than 10 μm width. The sensitivity was found to increase with decreasing gap size as well as with increasing line width.