Energy-gap modulation of boron nitride nanoribbons by transverse electric fields: First-principles calculations

TL;DR

This study uses first-principles calculations to demonstrate how transverse electric fields can significantly modulate and close the energy gaps of boron nitride nanoribbons with different edge structures, revealing distinct mechanisms for gap reduction.

Contribution

It provides a detailed analysis of energy gap modulation mechanisms in BN nanoribbons under electric fields, highlighting the effects of edge type and field direction, which was not previously well understood.

Findings

Energy gaps decrease with increasing electric field strength.

Gap can be completely closed at a critical electric field depending on ribbon width.

Different edge types exhibit distinct gap modulation mechanisms.

Abstract

Systematic ab initio calculations show that the energy gap of boron nitride (BN) nanoribbons (BNNRs) with zigzag or armchair edges can be significantly reduced by a transverse electric field and completely closed at a critical field which decreases with increasing ribbon width. In addition, a distinct gap modulation in the ribbons with zigzag edges is presented when a reversed electric field is applied. In a weak field, the gap reduction of the BNNRs with zigzag edges originates from the field-induced energy level shifts of the spatially separated edge-states, while the gap reduction of the BNNRs with armchair edges arises from the Stark effect. As the field gets stronger, the energy gaps of both types of the BNNRs gradually close due to the field-induced motion of nearly free electron states. Without the applied fields, the energy gap modulation by varying ribbon width is rather limited.