Characterization of silver coatings deposited from a hollow cathode source

Silver coatings of 15–50-μ thickness were deposited from a hollow cathode source with substrate bias voltage between 0 and −80 V, and deposition rates varied from 2 to 30 μ/min. A study of the relationship between the substrate bias voltage and the coating characteristics was made. The crystallographic orientation of the coating varied with bias voltage. The microstructure and microhardness of the coatings were also examined as a function of the bias voltage. The microstructure of the coatings resembled that of sputtered coatings; grain structure was changed from columnar to equiaxed by increasing the bias voltage. With the changes in the morphology of the microstructure, the microhardness of the coating also varied by a factor of 2. The coating fractured in a ductile mode and showed excellent adhesion to its substrate.