Carbon film nanocomposite for high-current field electron sources

Background and Objectives: Requirements and problems are formulated when creating cathode materials for high-current emission electronics. It has been shown that to create autocathodes with a current density of up to 100 A/cm$^2$ and above, the development of new nanostructured carbon materials with a surface density of nanodiamond edges of not less than 10$^6$–10$^8$ cm$^{-2}$ is necessary. Using a non-equilibrium low-pressure microwave plasma, the regions of regimes for obtaining carbon film coatings containing the diamond and graphite phases in various volume ratios are determined. Materials and Methods: Plasma-chemical deposition of carbon structures was carried out in a vacuum unit using a microwave ion-plasma source at a frequency of 2.45 GHz. Deposition was carried out on quartz and polycore substrates using ethanol vapor as a working substance at a pressure of from 0.05 Pa to 1.0 Pa. The substrates in the experiments were heated to a temperature of 300$\pm$10$^{\circ}$C. Studies of carbon structures were carried out using atomic-force and electron microscopy, as well as X-ray analysis and Raman scattering. Results: It was established experimentally and then substantiated using a cluster model of the structure of amorphous carbon, the influence of the mode of deposition of diamond-graphite film structures in the plasma of ethanol vapor on their field emission characteristics. The formation of more uniform and larger $\pi$-bonded graphite clusters helps to reduce the activation energy of conductivity in the composite structure and to improve the conditions of electron delivery to nanodiamond crystallites, which have a lower effective work function and higher degradation resistance. Conclusion: The developed technology of plasma-chemical deposition of nano-diamond graphite film structures allows the formation of emitters of cold electrons at temperatures from 250 to 350$^{\circ}$C. This makes it possible to combine it with other microelectronic production technologies.