Adhesion Behavior of Graphene Exfoliated from Silicon Substrate by Atomic Calculation

By applying a constant vertical upward velocity to graphene which was on silicon substrate, the adhesion behavior of graphene was observed. The effects of silicon substrate size, graphene layer number and exfoliation velocity on adhesion properties of graphene were studied. The influence of silicon substrate size on the exfoliation process can be ignored when it was 40 Ålarger than graphene. 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 graphene cannot be exfoliated. The top layer graphene was moved upward, meanwhile driving the second layer upward because of interlayer interaction between layers, as the velocity was in the range of 5.2 Å/ps~12 Å/ps. While the velocity increased greater than 12 Å/ps, the top layer was broken through the barrier of substrate and the second layer, then exfoliated alone. The velocity was extremely high to exfoliate graphene, and the adhesion energy was 299.81 mJ/m
²
, thus the adhesion between graphene and silicon was very strong.