THICKNESS EVOLUTION OF NICKEL NANO LAYER ON THE MICROSTRUCTURE AND ADHESION STRENGTH OF DLC FILMS

Abstract

Diamond-like carbon (DLC) films are metastable amorphous hydrogenated or non-hydrogenated forms of carbon, with excellent properties that make them reliable to use in various fields of science and technology. However, poor adhesion of DLC films to the substrate limits their performance. Using an interlayer is one of the methods to reduce the stress in films and improve the adhesion. In this study, different thickness of the nickel nano layers was deposited on the silicon substrates as an interlayer for the growth of DLC films. The Ni nano layers with the thickness of 10, 20, 40 and 80 nanometers were deposited on the substrates by DC magnetron sputtering while DLC films were synthesized by plasma enhancement chemical vapor deposition (PECVD) system with a mixture of argon and methane gases as the precursors. Morphology and the surface roughness of Ni interlayers were investigated by atomic force microscopy (AFM) which showed low surface roughness changing with thickness of interlayer. For the characterization of DLC films, Raman spectroscopy was used; it proved high degree of diamond-like character for the films grown on 10 nanometers nickel interlayer, as given by the ratio of I_D to I_G. FE-SEM (Field emission scanning electron microscopy) cross-section images of DLC films showed increasing of the thickness of DLC films by increasing of nickel nano layer thickness. The adhesion strength also was investigated by the nanoscratch test.