Generation Of "Graphene Arch-Bridge" On A Diamond Surface By Si Doping: A First-Principles Computational Study

We reveal the generation of the "Graphene Arch-Bridge" on a diamond (111) surface by Si doping via first-principles calculations. The "Graphene Arch-Bridge" is different from a simple graphene structure because both its ends are pinned to the diamond surface, and it has an interesting arched-type curved structure. The large stress around the doped Si atom leads to the transition of the six-membered C ring to a five-membered C ring. The C atom excluded from the ring by this transition changes from an sp(3) carbon to an sp(2) carbon and generates the "Graphene Arch-Bridge" on the diamond (111) surface. These results suggest that the generation of the five-membered C ring by stress due to the Si doping is the reason why the "Graphene Arch-Bridge" is generated. Finally, we propose that the "Graphene Arch-Bridge" is the origin of the experimentally observed super-low friction of Si-doped diamond-like carbon (DLC). Furthermore, we suggest that the "Graphene Arch-Bridge" leads to the lower wear properties of Si-doped DLC compared with nondoped DLC because its ends of the bridge are pinned to the DLC surface.