Gas sensing characteristics of p-type Cr₂O₃ and Co₃O₄ nanofibers depending on inter-particle connectivity

p-Type Cr₂O₃ and Co₃O₄ oxide semiconductor nanofibers, with different connecting configurations, were prepared by controlling the ultrasonic disintegration of nanofibers and their C₂H₅OH sensing characteristics were investigated. The ratios between resistances in 100 ppm C₂H₅OH, and air, of Cr₂O₃ (at 350 °C) and Co₃O₄ sensors (at 300 °C) consisting of long nanofibers were found to be 22.1 ± 1.4 and 82.4 ± 10.2, respectively. These values were significantly higher than those of Cr₂O₃ and Co ₃O₄ sensors (4.9 ± 1.1 and 5.7 ± 1.4), which consisted of less-connective primary particles disintegrated from nanofibers. The decrease of gas response, and increase in sensor resistance, with ultrasonic disintegration of nanofibers is explained in relation to a decrease of contact area between primary particles, indicating that inter-particle connectivity is a key parameter in determining the gas response of p-type oxide semiconductors.