Effect of low-pressure deposition on the mechanical and tribological properties of a-C:H films deposited via modified pulsed-DC PECVD with active screen as an additional cathode

Abstract

Due to their attractive mechanical, chemical, tribological, and biological properties, diamond-like carbon (DLC) coatings are widely used in many industrial applications. Normally, the deposition of amorphous hydrogenated carbon (a-C:H) films is obtained via the plasma-enhanced chemical vapor deposition (PECVD) technique. Recently, a modified pulsed-DC PECVD technique has attracted attention in this field due to its making it possible to grow a-C:H films at low-pressures (up to 0.1 Pa) in a collision less regime, leading to the achievement of improved mechanical and tribological properties. The incorporation of an additional cathode allows the confinement of electrons and ions, stabilizing and densifying the cold plasma at much lower pressure than conventional PECVD systems. This method is distinguished by higher energy and acceleration of the C+ ions, simpler reactor system equipment, and lower operating cost. In the present investigation, hydrogenated amorphous carbon films were grown on AISI 316 stainless steel using a thin amorphous silicon interlayer to improve interface adherence. The characterization of the coatings allowed identifying the influence of the deposition pressure on the microstructural, mechanical, and tribological properties and the film's adherence. The main results indicate that obtaining films with high hardness, low compressive stress, low coefficient of friction, high wear resistance, and appropriate adhesion is possible at deposition pressures almost 100 times lower than conventional PECVD techniques.