Discharge System with a Self-Heated Hollow Cathode and an Evaporating Anode in a Cusp Magnetic Field for Oxide Coatings Deposition

Abstract

The properties of a discharge with a self-heated hollow cathode and an evaporating anode placed in a cusp magnetic field created by two oppositely connected coils installed near the anode and cathode are studied. There is a negatively biased sample holder in the region of the annular magnetic slit. Compressing the discharge column at the anode with a magnetic field ensures effective evaporation of the metal (aluminum) loaded into the crucible anode; the density of the oxygen-containing plasma generated in the volume was controlled by changing the current of the cathode magnetic coil. The rate of depositing the aluminum oxide coating by reactive anodic evaporation, in contrast to reactive magnetron sputtering, is not limited by the oxidation of the sputtering target; the lifetime of the thermal emission cathode is hundreds of hours. The high ion-current density of the plasma (up to 10 mA/cm²) ensures a decrease in the crystallization temperature and the formation of nanocrystalline oxide coatings. The conditions are determined for a stable discharge operation with a current of up to 40 A at a pressure of 0.1 Pa in an oxygen-argon mixture. The results of probe diagnostics of the plasma discharge parameters, deposition rate measurements, and an analysis of the structure and properties of aluminum oxide coatings are given.