Nano-Scale Surface Structural Analysis of Hydrogen-Free DLC Films by Classical Molecular Dynamics

Shu SAWAI, Tomohisa KUMAGAI, Junho CHOI, Takahisa KATO
Journal of Japanese Society of Tribologists  
Hydrogen-free diamond-like carbon (DLC) films with many sp 3 bonding sites have a highly smooth surface, but very few studies have been carried out on the surface morphology of DLC films affected by the amorphous structure. In this study, the surface morphology of the DLC films was investigated on the basis of classical molecular dynamics simulations. The DLC samples composed of ten thousand carbon atoms were generated by the Melt-Quench scheme. We prepared 4 samples of various densities in
more » ... r to control the ratio of sp 2 / sp 3 sites in the structure. As the calculation results, the ratios of sp 3 sites of each structure were in proportion to the densities. We also found that the surface topography got rougher with a decrease in the sp 3 sites in the structures. Sp 2 -rich structure had huge graphite clusters which were the series of many graphite rings over the structure, making curved surfaces, resulting in the formation of rougher surface. We discussed that the relaxation process at sp 2 -rich sites in the amorphous carbon structure promoted graphitization and clustering to stabilize the entire amorphous structures, and that sp 3 -rich films made a smooth surface because sp 3 sites prevented carbon atoms from clustering.
doi:10.18914/tribologist.59.02_110 fatcat:zfsgjym6fnhldhjilj6cy5tm7q