Low voltage-high current discharge of Ti vapour in high vacuum

Abstract

A new type of discharge for ion plating has been investigated. A titanium vapour discharge is ignited on the electron beam evaporation source by applying a 22 V d.c. voltage to the anode which is located near the source. A dome-shaped plasma core is formed on the source and a strong blue light is emitted from the core. Changes in anode current (discharge current) ranging from ~ 2 A to over 100 A can be controlled by changing the anode voltage, electron beam gun power and electron-beam-scanning condition. Since the anode current immediately follows these changes, it is easy to control the discharge at will. Also, the ion collector current and ionization efficiency of titanium increase to ~ 20 A and over 100% respectively in keeping with the increase in anode current. This discharge is thus considered suitable for ion plating. This low voltage-high current discharge is closer to a vacuum arc discharge than to a glow discharge and this distributed discharge with no oscillation of the anode voltage and current is similar to the hot cathode arc but not the cold cathode arc. However, being a non-self-sustained discharge, it is not classified as a typical arc discharge.