Physical mechanics of bilayer graphene system

Tuning properties of graphene system is a key issue for its actual application in nanoelectronic devices. Our first-principles calculations reveal surprisingly high sensitivity of the field-induced energy gap of bilayer graphene to changes in its interlayer spacing. Small adjustments in the interlayer spacing near its equilibrium value produce large modulations in the gap over a wide range of field strength. For epitaxial bilayer graphene grown on SiC substrate, the first C layer or the buffer layer is electronically active to the second C layers in the presence of electric and mechanical tuning. The second graphene on C-terminated SiC exhibits an n-to-p-type transition under electric field, while the Fermi level of the second graphene on Si-terminated SiC is significantly shifted by compressing interlayer distance with respect to its buffer layer. These results provide insights for fundamental understanding and innovative device applications of bilayer graphene materials.