Simulation of Space Charge Effect in Field Emission from a Nanowire

At present, field emission from nanowires (NWs) is under intense investigation. In experiments, the dependence of field emission current from an NW on applied voltage (I--V behavior) often deviates from
the Fowler--Nordheim (FN) theory. We simulate the role of the space charge effect in the I--V behaviour of an NW. We determine the threshold electric field, at which the space charge effect starts to manifest itself, under different NW work functions. Our simulation result has confirmed that space charge effect is one of the possible factors responsible for the nonlinearity of the FN plots of an NW at high fields. Furthermore, our calculation reveals that the threshold field is related to the NW work function in an almost linear manner.