Residual gas effects on the emission characteristics of silicon field emitter arrays

Measurements have been performed on the degradation of emission from silicon field emitting devices in ultrahigh vacuum (UHV) and vacuums containing CO2 and CH4 with anode potentials of 0 and 2500 V. Degradation is very fast in CO2, slower in CH4, and very slow in UHV. Analysis of the data using a numerical simulation shows that, in UHV, the degradation can be explained by an increase in work function with time. For CO2 and CH4, however, it is primarily due to a blunting of the tips that is partly compensated for by a decrease in work function as emission progresses. There is some evidence for tip sputtering being important in the case of CO2 at high anode voltages.