Effect of electron temperature on the DLC film properties

It is well known that diamond-like carbon (DLC) films made by plasma chemical vapor deposition (CVD) have such excellent tribological characteristics that the lifetimes of machine tools and dies are considerably improved when the films are deposited on them. However, the application field has been somewhat restricted since the film-property control has been a little more difficult than other hard coatings like TiN and TiAlN. In this paper, we try to find out the key factors that control the film properties, from the viewpoint of plasma chemistry. The electron-density distribution in plasma is measured with a Langmuir probe while DLC films are formed on the specimen surfaces of both silicon and tungsten carbide (WC). Hardness and scratch tests are carried out to evaluate the mechanical characteristics of the films. The solid-state structures are investigated by Raman spectroscopy. As a result, it is shown that the electron temperature of plasma strongly affects the film properties such as friction, wear and hardness.