Simulating the Effect of Field Electron Emission from a Cathode with a Thin Dielectric Film on Its Sputtering in a Gas Discharge in an Argon and Mercury Vapor Mixture

Abstract

We propose a model for a low-current gas discharge in a mixture of argon and mercury vapor in the presence of a thin dielectric film on the surface of a cathode. The model takes into account that in such a mixture, a significant contribution to ionization of the working gas can be made by the ionization of mercury atoms during their collisions with metastable excited argon atoms. Positive charges accumulate in the discharge on the surface of the film, creating an electric field in the dielectric sufficient to induce field electron emission from the metal substrate of the electrode into the dielectric. These electrons are accelerated in the film by an electric field and can exit it into the discharge volume. This increases the effective ion–electron emission yield of the cathode. The temperature dependences of the discharge characteristics show that due to a rapid decrease in the concentration of mercury vapor in the mixture with decreasing temperature, the electric-field strength in the discharge gap and the discharge voltage increase. The presence of a thin dielectric film on the cathode can improve its emission properties and significantly decrease the discharge voltage. These phenomena result in a decrease in the energy of ions and atoms bombarding the cathode surface and, consequently, a reduction in the intensity of cathode sputtering in the discharge.