Hot hollow cathode and its applications in vacuum coating. A concise review

A concise description of the hollow cathode (HC) effect is given to clarify the confusing terminology and their diverse applications. The cold and hot types of HC’s are then discussed. It is followed by a summary of the behavior of the hot HC as an arc generating device, with emphasis on its use for vacuum coating purposes. Two major coating devices, one developed by Ulvac Corp. (Japan) and the other at the Rocky Flats Plant (RFP) of Rockwell International (USA), are then reviewed with their respective applications. Review of the latter includes recent results of plume effect upon both the unusual deposition rate distribution and the extremely high substrate (ion) current. The coating morphology and microstructure can be best explained using the Krikorian concept and, when optimized, can help to render very high bonding strength (as high as 90 ksi for 304 stainless steel substrates), with the coatings used as the bonding interlayer. Finally, comments are made concerning the directions of future technology...