CHANGE OF MATERIAL PROPERTIES AND CONTACT PERFORMANCE OF DLC FILM USING MOLECULAR DYNAMICS SIMULATION
Diamond like carbon (DLC) is widely used in engineering and scientific applications such as hard disk drive (HDD), biomedical and micro-electro-mechanical systems (MEMS) devices due to its mechanical strength, optical transparency, and chemical inertness. When DLC films carry out dynamic surface contact especially at hot/wet condition, its surface can experience oxidation process as well as mechanical stress and temperature rise by friction. For the ultra-thin DLC film (i.e., nanometers or less), it might be possible that oxygen atoms on the surface or within the DLC layer can change its material properties, accordingly affecting its contact performance thereafter. Therefore, it is of great importance to investigate the scientific relationship between DLC material properties and its oxidation process. So far researchers have studied the oxidation of DLC mostly through experimental methods. Wang et al. investigated the oxidation process of DLC using thermogravimetric (TGA) and differential thermal analysis (DTA), and found that graphitization and weight loss due to oxidation occurred at 350 C. Zhang et al. studied the thermal stability of oxidized magnetron sputtered DLC and its nanocomposite coatings. It was found that the magnetron sputtered DLC degraded at 300 C, while the DLC nanocomposite coatings could sustain temperature as high as 600 C. In this study, the thermal and mechanical properties of DLC film are quantitatively measured with respect to atomic percentage of oxygen atoms using molecular dynamics (MD) simulations.