Influence of the applied electric field and gas on the energy spectra of electrons emitted from carbon fibre microemitters

Electron emission from carbon fibre field emission source presented an inherent instability in the intensity of the emission spot in addition to current fluctuations. In this study, techniques were developed to obtain the best stabilization clearly demonstrating that the intensity fluctuations can be eliminated. Chart recorder traces and slow scans of optically monitored screen signals, that were recorded before and after treatment of the tip at various temperatures and for different periods are presented. The lifetime measurements of this cathode were recorded over a long period of time. This showed that noise is considerably smaller than that encountered with untreated tip. Stable emission currents permitted obtaining the energy distributions that had single peaks. The spectral shift from the Fermi level was analyzed and was shown to be a function of the emission current. After the initial treatment, the emission behavior showed no variation between heated and non-heated tips. The tip profile was examined using electron microscopy techniques. The influence of various residual gases on the emission characteristics was investigated. These gases, and in particular oxygen, produced no significant variation in the magnitude of the emission current or its stability. These and other properties of carbon fibre emitters have been interpreted in terms of a hot-electron emission mechanism.