Tuning the band gaps and work functions via topology and carbon concentration: a first-principles investigation of Cx(BN)y compounds

Abstract

The electronic properties, stabilities, and work functions of C(x)(BN)(y) monolayers were systematically investigated by first-principle techniques. The results indicated that the band gaps of the systems are rather sensitive to the topology and symmetry. However, the formation energies clearly suggested that the BN dimers tend to be grouped to one side and the carbon atoms are grouped to the other side. Such an atomic arrangement has the lowest formation energy and is thermodynamically highly stable, and furthermore their band gaps decrease gradually with an increasing of carbon content. Further analysis revealed that the band gap narrowing of G(I) structures depends on the nature of the C-2p(z) and N-2p(z) states. In contrast to the electronic properties, the variation of work functions as functions of carbon content exhibits an opposite trend. The strong correlation between the positive charge (Q(pos.)(tot.)) :work function (W(C(x)(BN)(y))) ratio and carbon content indicated that the ionicity of C(x)(BN)(y) compounds can be controlled by the carbon content and therefore determine the work functions of the systems.

Carbon-Doped Hexagonal Boron Nitride: Analysis as π-Conjugate Molecules Embedded in Two Dimensional Insulator

“…The structure with the minimum number of C-B and C-N bonds gives the lowest energy. This is also consistent with the previous reports [12][13][14][15][16][17][18][19][20][21][22][23][24]33]. Figure 3 shows the C-C bond length of these structures as a function of carbon content.…”

“…It is an intriguing difference from organic semiconductors as discussed in this paper [12,16,17,[19][20][21]. (3) The band gap values, and even the work function, are tunable by changing the composition [22]. (4) Some structures show magnetism (ferromagnetic or antiferromagnetic coupling within or beyond the domains) [16,19,23,24].…”

“…Synthetic attempts by chemical vapor deposition using well-defined synthesized molecules have started [9] and surface scientific techniques, such as scanning tunneling microscopy/spectroscopy, are revealing the relationship between the structure and the electronic properties [10,11]. Theoretical approaches have also been made from the association with graphene nanoribbons and two dimensional quantum dots [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The results of the previous studies can be summarized as follows: (1) C-C bonds are more stable than C-N or C-B bonds, and carbon atoms tend to segregate.…”

Lateral heterostructures of hexagonal boron nitride and graphene: BCN alloy formation and microstructuring mechanism

“…Consequently, far enough from the hBN core, hBCN becomes Gr, as is evident from the µ-LEED analysis presented in Figure 3. Spatial variation of the C:(B,N) ratio also effects the electronic structure of the hBCN alloy as visible in PEEM (see Supplementary Figure S1), where variations in work function [21] can provide spatially-dependent photoemission yield. LEEM data [ Figure 1(a)-(d)] clearly demonstrates more successful incorporation of the B x N y fragments into the growing hBCN alloy in the step-down direction of the Ir surface.…”

“…We do not observe simultaneous presence of the hBN and Gr moiré spots, which indicates that indeed the transition region from hBN to Gr is a locally homogeneous alloy. However, it is possible that separated hBN and Gr nano-domains, too small to provide a clear diffraction pattern, exist within hBCN, since calculations predict that phase segregation is energetically favorable [18][19][20][21]. It can be inferred from Figure 3(a) that the lattice constant of hBCN alloy changes from almost 2.48 Å [29] [lattice constant of hBN on Ir(111)] to 2.45 Å [28] [lattice constant of Gr on Ir(111)] as a function of the distance from the hBN edge.…”