Junction-Tuned SnO2 Nanowires and Their Sensing Properties

On the basis of a selective growth of SnO2 nanowires by the vapor-liquid-solid growth method, networked SnO2 nanowire sensors were fabricated. Then, their sensing properties were systematically investigated in terms of NO2. The density of junctions was controlled by altering the spacing of the patterned-interdigital electrodes (PIEs), on which SnO2 nanowires selectively grew and touched the nanowires grown on neighboring PIEs, eventually producing junctions. The sensing mechanism was attributed to the change not only in the width of the space charge region along the length direction of each nanowire but also in the height of the built-in potential at the junctions during adsorption and desorption of gaseous species. Narrower spacings of PIEs led to an increasing the density of junctions projected to the plane and, consequently, superior properties for gas sensing. Importantly, a general principle to prepare networked nanowires of superior sensing capabilities was suggested from the point of view of nanowire shape and electrode configuration.