Experimental study of field emission characteristics as a function of the emitter to anode distance

Abstract

It is experimentally shown that the relative fluctuation of field emission current reduces as the emitter to anode distance reduces, when the residual gas pressure in the vacuum is relatively high. The current fluctuation caused by the ion bombardment is proportional to PI product, where P is the residual gas pressure and I is the emission current. Decreasing the emitter to anode distance, the relative fluctuations of the emission current shift to a large PI product side. We speculate that the evidence may occur due to spatial shielding eflect of the anode. I. INTRODUCTION Fluctuation in the field emission current has been considered to occur due to migration of adsorbed gas molecules over the emitter surface and/or hitting of residual gas ions on the emitter surface [ 11-[4]. Standing on this understand, it is expected that the fluctuation can be reduced as the coming rates of the residual gas molecules and ions are reduced. When the emitter to anode distance is extremely short, the anode can prevent the emitter from coming residual gas molecules, a part of which hits the emitter surface as ions. Thus the fluctuation in field emission current is expected to become less as the emitter approach to the anode. Here we experimentally investigated the behavior of relative fluctuation in field emission current as. a function of emitter to anode distance. It is successfully shown that the relative fluctuation varies with the emitter to anode distance at a relatively high residual gas pressure in the vacuum of Torr range. 11. EXPERIMEN T