Effect of micro-gap on sensing properties to dilute chlorine gas of indium oxide thin film microsensors

Effects of micro-gap electrode on dilute Cl₂ gas sensing properties have been investigated for the In₂O₃thin film microsensors. The micro-gap electrodes with various gap size (0.1-2 μm ) were fabricated on SiO₂/Si substrate by means of MEMS techniques (photolithography and FIB). Then the In₂O₃ thin film was deposited on the electrode to be micro gas sensor. The resistance of In₂O₃ microsensor was increased upon exposure to dilute Cl₂ gas of ppm-level, while the sensor responded to Cl₂ gas less than 0.5 ppm with resistance decrease. Interestingly, in both cases the sensitivities were increased with decreasing gap size. The high sensitivity was obtained for In₂O₃ microsensor with 0.1 μm gap. The behavior was explained by the large contribution of interface between electrode and oxide at small gap and the high sensitivity at interface.