Rehybridization analysis of C atoms of Cu/Diamond and Ni/Diamond interfaces under vertical pressure

Diamond-like carbon (DLC) film enormous interest in both scientific and engineering communities because of its excellent tribological properties. And graphitization has been widely used to explain the low friction behavior of DLC film. However, the microscopic understanding of phase transition and graphitization mechanisms has never been conducted due to the limitations of existing characterization techniques. Herein, using first-principles calculations, we comparatively investigated the phase transition behavior of interface C atoms and the electronic structure information of the interface in the two interface models (Cu/Diamond and Ni/Diamond). The phase transition behavior is mainly due to the change in the hybridization mode of some C atoms at the interface under the vertical pressure, namely sp3 to sp2. We further used the transfer of the interface charge density to express the difference in tribological properties. The calculation results show that the re-hybridization behavior of interface C atoms has different effects on the charge transfer between the two interfaces. That is, there are different effects on its tribological properties. This work helps to understand the graphitization phenomenon under vertical pressure from the microscopic electronic structure.