Origin of multiple band gap values in single width nanoribbons

Abstract

Deterministic band gap in quasi-one-dimensional nanoribbons is prerequisite for their integrated functionalities in high performance molecular-electronics based devices. However, multiple band gaps commonly observed in graphene nanoribbons of the same width, fabricated in same slot of experiments, remain unresolved, and raise a critical concern over scalable production of pristine and/or hetero-structure nanoribbons with deterministic properties and functionalities for plethora of applications. Here, we show that a modification in the depth of potential wells in the periodic direction of a supercell on relative shifting of passivating atoms at the edges is the origin of multiple band gap values in nanoribbons of the same width in a crystallographic orientation, although they carry practically the same ground state energy. The results are similar when calculations are extended from planar graphene to buckled silicene nanoribbons. Thus, the findings facilitate tuning of the electronic properties of quasi-one-dimensional materials such as bio-molecular chains, organic and inorganic nanoribbons by performing edge engineering.

Effect of edge defects on band structure of zigzag graphene nanoribbons

“…II are 1.475 eV and 0.333 eV, respectively. For theoretical analyses, their one-dimensional potential profiles are plotted (Figure 5) and the potential well at global minimum is considered for comparative analysis 29 .…”

“…Similarly on the basis of potential profile, higher band gap value of even N z -ZGNRs than that of odd N z -ZGNRs are explained but needs normalization of potential depth w.r.t. width for comparison29 [supplementary material III]. The studies indicate that a change in arrangement of defects (sp 3 hybridized carbon atoms w.r.t.…”

Bandgap Tunability in a One-Dimensional System

“…The periodic average potential profiles of poly(anti-DThNDT) and poly(syn- DThNDT) are quite different to each other, and even to ideal rectangular potentials of Kronig-Penney model [36]. Since a system prefers to stay in its ground state; therefore the deepest potential well at global minimum in the periodic potential profiles are considered for comparative analysis of bandgap values [37] for isomeric systems. The global minimum for poly(anti-DThNDT) is located at 9.849 Å, enclosed between two crests (barriers) located at 9.058 Å and 11.432 Å, while global minimum for poly(syn-DThNDT) is located at 5.517 Å, enclosed between two crests (barriers) located at 4.466 Å and 6.480 Å.…”

Synthesis of WTe2 Nanowires with Increased Electron Scattering

“…By working with Weyl semi-metallic nanowires in the one-dimensional limit, it may be possible to combine the recent advances in inducing superconductivity by gating and proximity to further investigate predicted topological superconductivity and Majorana zero modes. Additionally, a bandgap may be induced in narrow WTe 2 nanowires, similar to graphene nanoribbons whose width determines the size of the bandgap induced by lateral confinement, although increased screening from higher carrier concentration may limit the magnitude of the induced bandgap in the case of WTe 2 . A practical benefit of creating nanowires of WTe 2 , and other TMDCs, is that three-dimensional (3D) gating configurations such as gate-all-around can be constructed around synthesized nanowires.…”