Microstructure analysis of plasma immersion ion implanted diamond-like carbon coatings

Abstract

This paper discusses the deposition of diamond-like carbon (DLC) coatings using Plasma Immersion Ion Implantation (PIII). Microstructure analysis indicates that an adhesion layer composed of carbides is formed by CH 4 implantation. Transmission electron microscopy and X-ray diffraction analysis indicates the absence of a long-range crystalline order in these carbides. It was also found that during the formation of the adhesion layer, a thin amorphous carbon layer is formed at the surface of the implanted layer. To promote the adhesion of the following DLC coating, it was found necessary to remove this amorphous carbon layer. This was accomplished by sputter-cleaning with Ar for several minutes and resulted in excellent adhesion of the DLC coatings. The formation of the amorphous carbon layer during CH 4 plasma immersion ion implantation is attributed (a) to the low duty cycles used in this process (the neutral species and the residual low energy ions are deposited on the surface during the off-period between pulses), and (b) to the low energy ions (below 1 keV) generated during the rise and fall times of the high-voltage pulses.