Study on bonding mechanism of graphene on silicon substrate

The study of bonding mechanism is important for the application of graphene in micro-electro-mechanical system (MEMS). Using molecular dynamics (MD) simulation, the adhesion behavior of graphene on silicon substrate was observed, by applying a constant vertical upward exfoliation velocity to graphene. The effects of silicon substrate size, graphene layer number and exfoliation velocity on adhesion properties of graphene were studied. The minimum velocity to exfoliate monolayer graphene was 4.3 Å/ps, and the maximum adhesive force was 25.04 nN. For two-layer graphene, velocity was applied on the top layer, 5.2 Å/ps and 12 Å/ps were the critical velocities: when the velocity was no more than 5.2 Å/ps, the top layer cannot be exfoliated; as the velocity was in the range of 5.2-12 Å/ps, the second layer was driven upward together with the top layer, because of interlayer interaction between graphene layers; when the velocity increased greater than 12 Å/ps, the top layer graphene was broken through the bonding forces of substrate and the second layer, and exfoliated alone. It can be concluded that the velocity to exfoliate graphene was extremely high, and the adhesion energy was 299.81 mJ/m² and 323.41 mJ/^m2 for exfoliating monolayer and two-layer graphene respectively, thus the adhesive strength between graphene and silicon was very strong.