Multi-junction joints network self-assembled with converging ZnO nanowires as multi-barrier gas sensor

A novel sensor assembled with ZnO nanowires (NWs) joints has been successfully demonstrated to show a high response and fast response/recovery to ethanol gas. The multi-junction ZnO NWs joints have been grown directly on the micro-scale interdigitated electrodes (μIDEs) at low temperature using a creative solution process assisted by a conventional lithography technique. The conductance of the NWs network-based device varies significantly and rapidly as the concentration of ethanol gas, which reveals a high response and quick response/recovery of the sensor. Its superior performance can be explained by the enhanced surface reaction of the ethanol molecules with the oxygen defects, resulting from the large length-to-diameter aspect and the high surface-to-volume ratio of the thinner NWs. Additionally and fancifully, the sensing mechanism of coupled double barriers (CDBs) at the multi-junction joints was applied to analyze the response of this sensor. The quick diffusion of ethanol molecules into and out of NWs contributes to quick response and recovery, deriving from the joints network structure directly grown on the μIDEs.