Energetics and Electronic Structure of Triangular Hexagonal Boron Nitride Nanoflakes

Mina Maruyama,Susumu Okada

doi:10.1038/s41598-018-34874-x

Abstract

We studied the energetics and electronic structures of hexagonal boron nitrogen (h-BN) nanoflakes with hydrogenated edges and triangular shapes with respect to the edge atom species. Our calculations clarified that the hydrogenated h-BN nanoflakes with a triangular shape prefer the N edges rather than B edges irrespective of the flake size. The electronic structure of hydrogenated h-BN nanoflakes depends on the edge atom species and their flake size. The energy gap between the lowest unoccupied (LU) and the highest occupied (HO) states of the nanoflakes with N edges is narrower than that of the nanoflakes with B edges and the band gap of h-BN. The nanoflakes possess peculiar non-bonding states around their HO and LU states for the N and B edges, respectively, which cause spin polarization under hole or electron doping, depending on the edge atom species.

Highlights

Hexagonal boron nitride (h-BN) is known to be a prototypical layered material in which each layer is composed of B and N atoms alternately arranged in an hexagonal network similar to that of graphite[1,2,3,4]
We investigated the geometric and electronic properties of triangular hexagonal boron nitrogen (h-BN) nanoflakes with hydrogenated N or B edges using density functional theory with the generalized gradient approximation, to provide theoretical insight into the preferential formation of triangular flakes with N edges in chemical vapor deposition (CVD) experiments
Our calculations showed that triangular h-BN nanoflakes with hydrogenated N edges are more stable by approximately 0.5 eV per atom than those with hydrogenated B edges for all flake sizes studied here and for any B source

Summary

Introduction

Hexagonal boron nitride (h-BN) is known to be a prototypical layered material in which each layer is composed of B and N atoms alternately arranged in an hexagonal network similar to that of graphite[1,2,3,4]. Because of the structural similarity of h-BN to graphene, h-BN nanoflakes with triangular shapes may possess a similar non-bonding state near their occupied state and unoccupied state edges, depending on the edge terminations[21]. We aim to investigate the energetics and electronic structure of triangular h-BN nanoflakes with respect to their sizes and edge terminations to provide theoretical insight into the formation mechanisms of triangular h-BN with hydrogenated N edges during CVD experiments. The electron states of the nanoflakes with N edges around the HO states possess a non-bonding nature for the flakes with hydrogenated N edges, which causes spin polarized ground states under hole doping by the gate electrode

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