Gradient metal—a-C:H coatings deposited from dense plasma by a combined PVD/CVD process

Abstract

In this paper, a combination of plasma based PVD- and CVD-processes is described which allows to deposit metal-nonmetal layer systems without and with gradient transition between the metallic and the non-metallic phase. A magnetically confined low pressure arc plasma of high density (order of n c= 10 12cm −3) is produced into which metal atoms and reactive gases are introduced in sequence to deposit interlayers and coatings. The depositing species are mostly ions which allows the control of the energy of the incident particles, and thus the structure and properties of the deposit. In order to demonstrate the feasibility of a continuous transition from PVD- to CVD-deposition, aluminium interlayers and subsequently a-C:H layers were deposited on stainless steel and Si (100) substrates. The Al-layer was formed by ionizing and depositing a flow of evaporated Al, whereas for the a-C:H deposition hydrocarbon precursor gases were dissociated and ionized. During the overlap period of both processes a carbide interface was formed. The deposited layers were characterized by SEM, TEM, SIMS, etc. It was found that by the use of the Al/Al 4C 3-interlayer delamination of the a-C:H coatings could be strongly reduced allowing an increase of the a-C:H thickness to 2–3µm.