Tribological Properties of Ultrathin DLC Films with and without Metal Interlayers

Abstract

The tribological properties of ultrathin films with a single metal layer between the Si substrate and the thin film were investigated. A DC magnetron sputtering method and a radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) method were employed to synthesize the metal interlayer and the diamond-like carbon (DLC) film, respectively. Three different metals (chromium, nickel, and titanium) were used as the interlayers between the Si substrate and DLC thin film. In this study, we compared the tribological properties of four different samples; DLC film without any metal interlayer, and DLC films with interlayers of three different metals. The thicknesses of the films were observed with a field emission scanning electron microscope (FE-SEM), and a detailed structure of the DLC thin films with and without the metal interlayer was investigated by using a transmission electron microscope (TEM) and auger electron spectroscope (AES). Also, the surface morphology of the film was found to be less than 0.4 nm by using an atomic force microscope (AFM). The residual stress and the surface energy of all the samples were measured by using a stress tester and contact angle measurements. The tribological performances of the DLC films with and without metal interlayers were observed microscopically by using the friction force microscope (FFM) mode during the AFM measurement and Ball-on-Disk (BOD) measurements. The Cr interlayer was found to be the most suitable material among the metals used in this study to improve the tribological properties of ultrathin DLC films.