The effects of gas exposure and UV illumination on field emission from individual ZnO nanowires

Individual ZnO nanowires grown on a Pt tip were exposed to O-2 and H-2 in the course of field emission. O-2 exposure was found to suppress field emission, while H-2 reduced the turn-on voltage and increased the emission current. Upon UV ( 250-400 nm) illumination, the emission current increased almost immediately by about two orders of magnitude, but takes a much longer period, depending on the vacuum level, to fall to its original value following illumination. These phenomena can be accounted for with reference to mechanisms responsible for the sensitivity of metal oxides to oxidizing and reducing gases.