Some characteristics of non-self-maintained discharge in metal vapor

Abstract

The method of metal evaporation in a vacuum by a nonself-maintained discharge is applied as for deposition of thin films and coatings, and as for diffusion saturation of metallic materials. Change of the thermoionic cathode temperature and discharge power provides the evaporator work in wide interval of currents (1-100 A) and voltages (30-700 V), initiating the fluxes of deposited atoms with ionization degree from 2 to about 100%. The dependence of initiation conditions and discharge burning were considered due to vacuum, the evaporated metals, the cathode/anode distance and the cathode temperature in voltage range from 50 to 500 V with currents to 5 A. The conditions of discharge initiation are improved with decreasing basic pressure in chamber lower than 0.01 Pa. The increasing of pressure lead to burning of the shunting glow discharge through residual gases. The optimal cathode temperatures are in range from 1800 to 2200/spl deg/C. The plasma parameters were determined from I-V characteristics of a Langmuir probe. The temperature and density of the plasma electrons are changed in intervals, respectively, (8-12) /spl times/10/sup 4/ K and (0.4-5)/spl times/10/sup 1 /cm/sup -3/. The density of ion current was 5 mA cm/sup -2/. Maximum values of ionization degree for evaporated Cu, Cr and Al atoms are attained at 100,200 and 250 V, respectively, and are of the range 30-50%.