Effect of calcination temperature on interface properties between In2O3 and an electrode in micro gap semiconductor gas sensors

The In2O3 thin film micro sensors were fabricated by dropping In(OH)(3) Sol on micro gap electrode with OA-2.5 mu m of gap size, dried, and calcined at various temperatures. The grain size of In2O3 and thus the number of In2O3 grains were changed by calcining at 600-850 degrees C. The size of grain was increased from 15 mu m at 600 degrees C to 55 nm at 850 degrees C, and thus the number of grains in 0.3 mu m gap was decreased from 19 to 5.3. Contrary to the expectation, the small resistance changes to both 1 ppm Cl-2 (resistance increase) and 0.5 ppm Cl-2 (resistance decrease) were obtained for In2O3 micro sensors calcined at 700-850 degrees C. These were contributed to the changes in the surface and interface chemical State to suppress the adsorption of or the substitution with Cl-2 molecule.