Emission properties of field cathode tips and structures with quantum wells

Abstract

A calculation of the potential barrier shape at the metal-vacuum interface was carried out taking into account the effects of the spatial dispersion and dynamic corrections to the image force potential. The calculations were carried out using the random phase approximation (RPA) (for the concentration of conductivity electrons n<or=1020 cm-3) and the Hubbard approximation for n>or=1021 cm-3. Current-voltage characteristics were obtained for field emission both from the bulk material (with a non-quantized electron spectrum) and from thin films (with quantized electron spectra). The field emission (FE) from the thin films was shown to increase substantially due to the effective decrease of the work function. The quantization of electron spectra in quantum wells and, consequently, the decrease of the work function lead to a substantial increase of FE from planar and non-planar emitters covered by thin metallic films. The combined influence of the emitter shape and electron spectrum quantization on FE properties can be pronounced even under moderate and low external fields. The effect of the cathode shape on the emission properties was also analysed. The results obtained make it possible to optimize the structure and the shape of emitter tips for the tip array structure production.