A Study on Interface Strength of a-Si:H-DLC Film

Abstract

In this study a method to deposit a-Si:H-DLC film at room temperature has been explored by CVD. The interface structure of a-Si:H-DLC film and the compositions of DLC film were studied, the adhesion strength of DLC film deposited directly on metal substrates was very poor, there was an almost complete crack at interface between DLC film and metal substrates, the local shedding could also be observed on surface of DLC film. After inserting a-Si:H intermediate material into the interface, the adhesion strength of a-Si:H-DLC film was improved well, the a-Si:H intermediate layer with about 0.2μm thickness was formed, and was very impact. In addition the structures of DLC film mainly were graphite structure with SP2 bonding, and contain a certain amount of diamond structure with SP3 bonding. Load capacity of a-Si:H-DLC film deposited on the metal substrates was also evaluated, as the contact stress (Hertz stress) was less than 544MPa for the film with 1μm-thickness, the failure life was up to 100 million cycles or more by using “ball- on- disk” wear testing machine, therefore it could be used in practice. Changes in load had little effect on friction coefficient.