Substrate-induced band gap in graphene on hexagonal boron nitride:Ab initiodensity functional calculations

Abstract

We determine the electronic structure of a graphene sheet on top of a lattice-matched hexagonal boron nitride ͑h-BN͒ substrate using ab initio density functional calculations. The most stable configuration has one carbon atom on top of a boron atom, and the other centered above a BN ring. The resulting inequivalence of the two carbon sites leads to the opening of a gap of 53 meV at the Dirac points of graphene and to finite masses for the Dirac fermions. Alternative orientations of the graphene sheet on the BN substrate generate similar band gaps and masses. The band gap induced by the BN surface can greatly improve room temperature pinch-off characteristics of graphene-based field effect transistors.

Gaps induced by inversion symmetry breaking and second-generation Dirac cones in graphene/hexagonal boron nitride

“…Second, although the maximum gap at the equilibrium layer separation for a perfectly lattice matched heterostructure is predicted to be approximately 50 meV (ref. 13), the gap size increases sharply upon reducing the separation between the graphene and h-BN layers 13 . A bandgap opening at the graphene Dirac cone and SDCs can be induced by an inversion-asymmetric mass term in the perturbation potential 10,21,23 , and the mass term can vary by orders of magnitude depending on the assumptions used 13,28,29 .…”

“…13), the gap size increases sharply upon reducing the separation between the graphene and h-BN layers 13 . A bandgap opening at the graphene Dirac cone and SDCs can be induced by an inversion-asymmetric mass term in the perturbation potential 10,21,23 , and the mass term can vary by orders of magnitude depending on the assumptions used 13,28,29 . Shortening of the layer separation between graphene and h-BN by 0.2 Å around the equilibrium distance can result in an almost threefold increase of the local mass term 13 .…”

“…A bandgap opening at the graphene Dirac cone and SDCs can be induced by an inversion-asymmetric mass term in the perturbation potential 10,21,23 , and the mass term can vary by orders of magnitude depending on the assumptions used 13,28,29 . Shortening of the layer separation between graphene and h-BN by 0.2 Å around the equilibrium distance can result in an almost threefold increase of the local mass term 13 . Third, the substantial out-of-plane height variation of 0.6 Å and 0.2% in-plane strain revealed by atomic force microscopy (AFM) measurements suggest sufficiently large variations in the local mass term and can produce a large average gap 13,25 .…”

“…Shortening of the layer separation between graphene and h-BN by 0.2 Å around the equilibrium distance can result in an almost threefold increase of the local mass term 13 . Third, the substantial out-of-plane height variation of 0.6 Å and 0.2% in-plane strain revealed by atomic force microscopy (AFM) measurements suggest sufficiently large variations in the local mass term and can produce a large average gap 13,25 . Therefore, the large gap size suggests that our epitaxially grown graphene/h-BN samples have much stronger short-range interlayer interaction than the weak van der Waals interaction as commonly believed in ideally flat structures.…”

Observation of an intrinsic bandgap and Landau level renormalization in graphene/boron-nitride heterostructures

“…In particular, graphene/h-BN heterostructures have shown great potentials for band structure engineering of graphene [8][9][10][11][12][13][14][15][16][17][18][19][20] including inducing a bandgap 11,13,[15][16][17][18][19][20] (Fig. 1a), which is of great fundamental [21][22][23][24] and technological 25 interest.…”