The feasibility of using a carbon fibre field emitter as an elctron source in cathode ray tubes

Abstract

An ultra high vacuum electron optical bench has been designed to develop a demountable prototype tube using a computer designed two-anode electrostatic lens to focus the beam. This system has demonstrated that a carbon fibre field emitter has a satisfactory electron optical performance in a CRT and an adequate lifctimc. However, there is a residual problem of emitter instabilities which lead to the visual display flickering. The energy spectra of the emitted elecLrons have been measured using an UHV high resolution spectrometer. The half-width and spectral shift were both found to increase with increasing field. Electroluminescence has also been found to accompany the electron emission. Since flucLuations in the final image are almost certainly related to instabil­ities in the emission current, various stabilisation tech­niques have been investigated. The noise characteristics of the emission current have been analysed and related to the instability of the emission image as recorded cinemato­graphically, which showed the pattern to consist of individual spots which "switch-on" and "switch-off". Scanning electron microscopy has revealed that the onset of emission is accompanied by an explosion of the emitter endform. To explain the experimental observations a model has been proposed for the emission mechanism based on a composite emission regime involving an insulating amorphous pocket overlaying a metallic-like substrate.