Vacuum-plasma processes at extreme field emission in diamond electron sources

Background and Objectives: The use of high-current field electron sources that satisfy various circuitry requirements as a part of electronic devices for various purposes suggests the possibility of matching their operation modes with the operating characteristics of the devices, as well as high reproducibility of emission parameters, stability and the necessary resource of reliability and durability. The stability and durability of field electron sources are extremely sensitive to the changes in the geometry of emission centers and to the state of their surface, which undergoes various destructive influences during operation. These changes are especially important in the case of high-current field-emission cathodes, which, as a rule, work under conditions of technical vacuum and high electric field intensities. The aim of the work was to study the possibility of creating field sources of electrons based on thin-film planar-end nanodiamond-graphite structures that satisfy various circuit requirements, as well as to study fundamental factors that lead to a change in their I–V characteristics and limit the maximum value of their field emission currents, stability and durability of high-current field emission. Materials and Methods: Emission structures were made of carbon films deposited in a microwave plasma of a low pressure gas discharge. The surface resistance of the films was 120 kOhm/□ and 1.2 mOhm/□. In the first type of emission structure, diamond-graphite films were mechanically separated into two parts. One part of the film was the cathode, the second served as the anode. Measurement of field emission characteristics in vacuum (2–4)·10-3 Pa. Between the cathode and the anode, voltage pulses with a duration of 10 μs and an amplitude of 0 to 3000 V were applied. In the second type of emission structure, field emission was carried out from the end face of a diamond-graphite film deposited on a polycor substrate. Field emission-voltage characteristics were measured in constant electric fields. Determination of the elemental composition of the surfaces of field emission structures after electrical tests was carried out using an energy dispersive microanalysis system. Results: It is shown that the steepness of the current-voltage characteristics, as well as the stability and durability in extreme operating conditions of high-current field electron sources based on film diamond-graphite nanocomposites, is determined by their surface resistance. Electron fi