Modified Diamond-Like Carbon Multilayer Coatings on Metallic Substrates Produced by Pulsed-DC Hollow Cathode PECVD

摘要

Diamond-like carbons (DLCs) have attracted much interest in recent decades, and have found a wide range of applications, including in optoelectronic devices, solar cells, infrared optics and, notably, as protective coatings for metals in corrosive and/or abrasive environment. These consist of the amorphous hydrogen-carbon alloys (a-C:H), hydrogen-free amorphous carbons (a-C) and tetrahedrally-structured amorphous carbons, (ta-C), which can contain in excess of 90% sp~3 bonding. In this paper, modified a-C:H type diamond-like carbon multilayer films have been deposited on a range of metallic substrates: nickel aluminium bronze, copper and 80/20 cupronickel alloy by pulsed-DC hollow cathode PECVD. The effects of substrate plasma pretreatment on the structure of both the substrate itself, and the structure and properties of the coating are considered. The protective effect of these coatings has been demonstrated by electrochemical techniques. The coatings are further characterized by Raman spectroscopy (with particular regard to the C-C sp~2/sp~3 bonding ratio), surface energy determination, SEM, and nanoindentation.