Nanoscale probing of image-potential states and electron transfer doping in borophene polymorphs

TL;DR

This study uses advanced spectroscopy to analyze image-potential states in borophene polymorphs, revealing substrate-induced electron transfer effects that challenge existing self-doping models.

Contribution

It provides nanoscale insights into borophene's electron transfer behavior and demonstrates the influence of substrate effects on doping levels.

Findings

Electron transfer occurs from Ag(111) to borophene.

Denser v_1/6 borophene shows higher doping than v_1/5.

Substrate effects significantly influence borophene doping.

Abstract

Using field-emission resonance spectroscopy with an ultrahigh vacuum scanning tunneling microscope, we reveal Stark-shifted image-potential states of the v_1/6 and v_1/5 borophene polymorphs on Ag(111) with long lifetimes, suggesting high borophene lattice and interface quality. These image-potential states allow the local work function and interfacial charge transfer of borophene to be probed at the nanoscale and test the widely employed self-doping model of borophene. Supported by apparent barrier height measurements and density functional theory calculations, electron transfer doping occurs for both borophene phases from the Ag(111) substrate. In contradiction with the self-doping model, a higher electron transfer doping level occurs for denser v_1/6 borophene compared to v_1/5 borophene, thus revealing the importance of substrate effects on borophene electron transfer.