One Dimensional Nearly Free Electron States in Borophene

TL;DR

This study reports the observation of one-dimensional nearly free electron states in borophene, revealing their origin from line defects and potential for electronic applications, using combined experimental and computational methods.

Contribution

It demonstrates the existence of NFE states in borophene on Ag(111), linking them to structural defects and in-plane potential wells, which is a novel insight into borophene's electronic properties.

Findings

NFE states observed in borophene on Ag(111)

NFE states originate from line defects in borophene

Potential applications in transport and field emission devices

Abstract

Two-dimensional boron (borophene) is featured by its structural polymorphs and distinct in-plane anisotropy, opening opportunities to achieve tailored electronic properties by intermixing different phases. Here, using scanning tunneling spectroscopy combined with first-principles calculations, delocalized one-dimensional nearly free electron states (NFE) in the (2,3) or \b{eta}12 borophene sheet on the Ag(111) surface were observed. The NFE states emerge from a line defect in the borophene, manifested as a structural unit of the (2,2) or \c{hi}3 sheet, which creates an in-plane potential well that shifts the states toward the Fermi level. The NFE states are held in the 2D plane of borophene, rather than in the vacuum region as observed in other nanostructures. Furthermore the borophene can provide a rare prototype to further study novel NFE behaviors, which may have potential applications on transport or field emission nanodevices based on boron.