Measurement of Photoelastic Constant of Diamond-like Carbon Film

抄録

Diamond-like carbon (DLC) films have excellent properties such as high hardness, wear resistance and low friction coefficient. Therefore, DLC is used for surface treatment in the fields of cutting tools, molds, automobile industry, medical care, nanotechnology, etc. Since the reliability of the DLC films are evaluated by their adhesion to the substrate, a quantitative evaluation method for it is desired. The adhesion can be evaluated by the residual stress of the film, but the optimum nondestructive measurement method for it has not been established. Therefore, we propose a residual stress measurement method using the photoelastic method. This paper describes the method and results for obtaining the photoelastic constant of DLC. In this study, DLC films were formed on a glass substrate by plasma enhanced chemical vapor deposition. Then, from the warpage of the substrate due to the residual stress of DLC, the residual stress was calculated using the Stoney equation. On the other hand, the retardation of the DLC film was measured by the photoelastic experiment. The photoelastic constant of the DLC, 5.13 x 10-11 Pa-1, was obtained from the obtained relation between the residual stress and retardation.