Characterization of silicon nanoporous pillar array as room-temperature capacitive ethanol gas sensor

A room-temperature capacitive ethanol sensor was fabricated based on a silicon nanoporous pillar array (Si-NPA) and the corresponding ethanol gas sensing properties were studied. With ethanol concentration changing from 0 to 500 ppm, a capacitance increase over 430% was achieved at a signal frequency of 200 Hz. The device response was found to be concentration dependent, lower at low concentration and higher at high concentration. The response and recovery times measured at 50 ppm ethanol concentration were about 15 and 30 s, respectively. The sensor showed long-term stability; the capacitance measured under the same conditions remained almost unchanged during 40-week storage. The high performances of Si-NPA ethanol gas sensors were attributed to the enlarged sensing area arising from the numerous nanopores, the effective mass transportation pathway brought by the regular pillar array, and the stable surface status resulted from the strong iron-passivation. Our results indicated that Si-NPA might be a promising sensing material to fabricate practical room-temperature ethanol gas sensors.