Native defects in hybrid C/BN nanostructures by density functional theory calculations

Abstract

First-principles calculations of substitutional defects and vacancies are performed for zigzag-edged hybrid C/BN nanosheets and nanotubes which recently have been proposed to exhibit half-metallic properties. The formation energies show that defects form preferentially at the interfaces between graphene and BN domains rather than in the middle of these domains, and that substitutional defects dominate over vacancies. Chemical control can be used to favor localization of defects at C-B interfaces (nitrogen-rich environment) or C-N interfaces (nitrogen-poor environment). Although large defect concentrations have been considered here (10 6 cm −1 ), halfmetallic properties can subsist when defects are localized at the C-B interface and for negatively charged defects localized at the C-N interface; hence the promising magnetic properties theoretically predicted for these zigzag-edged nanointerfaces might not be destroyed by point defects if these are conveniently engineered during synthesis.

Electromechanical response at polar zigzag boundaries in hybrid monolayers

“…High-resolution scanning tunneling microscopy images showed that zigzag interfaces are preferably formed [3,5]. A number of very recent experiments have observed that in these zigzag boundaries between graphene and h-BN domains, novel interfacial electronic states appear [6][7][8], thus confirming early theoretical predictions [9][10][11][12][13][14][15][16].…”

“…As in previous works [13,15], here we consider coplanar geometries composed of two-dimensional superlattices made from n zigzag chains of graphene and m zigzag chains of BN, periodically repeated along the interfacial direction. We label these superlattices as (n,m), or, alternatively, C n (BN) m .…”

“…1(b), hence avoiding the intrinsic difficulties to simulate electric fields under periodic boundary conditions (due to the intrinsic nonperiodic nature of the position operator [35]). In particular, we model (8,8) armchair nanotubes with zigzag-edged C/BN domains composed of n = 5 zigzag chains of C and m = 11 zigzag chains of BN along the tube axis, following the geometries discussed in the literature [10,11,14,15,25]. This chirality and chemical composition result in a half-metallic ground state [15].…”

“…In particular, we model (8,8) armchair nanotubes with zigzag-edged C/BN domains composed of n = 5 zigzag chains of C and m = 11 zigzag chains of BN along the tube axis, following the geometries discussed in the literature [10,11,14,15,25]. This chirality and chemical composition result in a half-metallic ground state [15]. An additional set of ghost orbitals (s and p like) cylindrically distributed around the tube axis are used to improve the description of nearly free electron states known to exist in BN nanotubes [36].…”

First principles molecular dynamics study of nitrogen vacancy complexes in boronitrene

“…Such hybrid nanostructures -in particular, graphene flakes embedded in the h-BN monolayer -possess tuneable magnetic moments [31,32], among many other interesting electronic properties. Negatively charged h-BN nanostructures have been obtained by postsynthetic doping with substitutional carbon impurity by in situ electron beam irradiation inside the transmission electron microscope [33,34].…”