Origin of multiple band gap values in single width nanoribbons

TL;DR

This paper explains why graphene nanoribbons with the same width can have multiple band gap values, attributing it to edge atom shifts affecting potential wells, which impacts their electronic property tuning.

Contribution

It reveals the origin of multiple band gaps in nanoribbons with identical widths, linking it to edge atom shifts and potential well modifications, applicable to various 1D materials.

Findings

Multiple band gaps arise from edge atom shifts affecting potential wells.

The phenomenon is consistent in graphene and silicene nanoribbons.

Edge engineering enables tuning of electronic properties in 1D materials.

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 gap values commonly observed in the same width of graphene nanoribbons fabricated in same slot of the experiments remains 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 for the same width of nanoribbons 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.