Reversible response of field emission from ZnO nanowire to exposure to gases

The effect of gaseous O₂, N₂, and air on the field emission (FE) properties of ZnO nanowires (ZNWs) was investigated. The ZNWs showed a reversible dependence of the FE, with a rapid response on variations in vacuum pressure (VP). The FE properties of ZNWs were fully recovered after evacuation to the initial VP, even after an abrupt current drop, induced by the presence of all gases tested, under a severe vacuum condition of ∼2 × 10^-4 Torr. A steady-state emission current with no detectable current degradation was obtained at each VP over an approximately a 4-hr period. The present findings suggest that ZNWs are promising candidates for use as robust field emitters. However, the dependence of the FE current on the VP might also be useful in further applications. A possible mechanism, based on a change in work function due to adsorbed molecules, for the reversible response of the FE from ZNWs is discussed.