Abstract
Poor electron-related cutting current in graphene-based field-effect transistors (FETs) can be solved by placing a graphene layer over a hexagonal boron nitride (BN) substrate, as established by Giovannetti et al. and other researchers. In order to produce high-quality results, this investigation uses 2 × 2 cells (~2.27% mismatch), given that larger cells lead to more favourable considerations regarding interactions on cell edges. In this case, the substrate-induced band gap is close to 138 meV. In addition, we propose a new material based on graphene on BN in order to take advantage of the wonderful physical properties of both graphene and BN. In this new material, graphene is rotated with respect to BN, and it exhibits a better mismatch, only ~1.34%, than the 1 × 1-graphene/1 × 1-BN; furthermore, it has a very small bandgap, which is almost zero. Therefore, in the bands, there are electronic states in cone form that are like the Dirac cones, which maintain the same characteristics as isolated graphene. In the first case (2 × 2-graphene/2 × 2-BN), for example, the resulting band gap of 138 meV is greater than Giovannetti’s value by a factor of ~2.6. The 2 × 2-graphene/2 × 2-BN cell is better than the 1 × 1-graphene/BN one because a greater bandgap is an improvement in the cutting current of graphene-based FETs, since the barrier created by the bandgap is larger. The calculations in this investigation are performed within the density functional theory (DFT) theory framework, by using 2 × 2-graphene/2 × 2-BN and 13 × 13-graphene/23 × 23-(0001) BN cells. Pseudopotentials and the generalized gradient approximation (GGA), combined with the Perdew–Burke–Ernzerhof parametrization, were used. Relaxation is allowed for all atoms, except for the last layer of the BN substrate, which serves as a reference for all movements and simulates the bulk BN.
Highlights
Materials such as graphene and boron nitride (BN) are highly valued in cutting-edge nanotechnologies
We did not find in the literature formation energy values for the graphene/(0001)BN-surface structure with the same configurations considered in this investigation
density functio√nal the√ory (DFT) calculations were carried out regarding the graphene/BN interface, seeking to propose new structures that can improve some electronic or optoelectronic devices, such as F√ET’s √based on graphene
Summary
Materials such as graphene and boron nitride (BN) are highly valued in cutting-edge nanotechnologies. The present investigation uses 2 × 2 cells, given that the software used to calculate DFT-based mechanical-quantum properties smoothens the effect over the edges when a cyclic crystal lattice is chosen. This can be evidenced by comparing the band gaps of the BN/graphene junction obtained by Giovannetti et al [29] (53 meV) and those of this investigation (138 meV). In the case of field-effect transistors (FETs), Giovanetti et al propose a structure of graphene over BN that opens a gap between the Dirac cones [29]. The calculations were performed within the framework of density functional theory
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