Trilayer graphene has two nearly degenerate stacking configurations, ABA and ABC depending on the position of the top most layer of carbon atoms. In an electric field, the ABC configuration opens a band gap that is tuned by the strength of the field while ABA graphene remains metallic. Therefore, in an electric field trilayer graphene prefers to be in the ABC configuration because it lowers the total energy.
Using scanning tunneling microscopy and spectroscopy, we have oberserved the movement of the boundary between the ABA and ABC stacked regions in trilayer graphene. We have found that as the gate voltage (electric field) increases the boundary moves such that the ABC region expands. The movement is determined by the balance between the energy gained from opening the band gap and the energy cost of stretching the domain wall. This work was published in Nature Materials