Simulated scanning tunneling microscopy images of few-layer-phosphorus capped by graphene and hexagonal boron nitride monolayers

TL;DR

This study uses ab initio calculations to simulate STM images of phosphorus allotropes capped with graphene or h-BN, revealing how these layers influence the ability to distinguish underlying structures.

Contribution

It demonstrates that h-BN capping preserves STM distinguishability of phosphorus phases, unlike graphene, providing insights into surface imaging of protected phosphorus materials.

Findings

h-BN capping allows phase distinction in STM images

Graphene capping masks underlying phosphorus structure

STM imaging remains effective with certain protective layers

Abstract

Elemental phosphorous is believed to have several stable allotropes that are energetically nearly degenerate, but chemically reactive. To prevent chemical degradation under ambient conditions, these structures may be capped by monolayers of hexagonal boron nitride ({\em h}-BN) or graphene. We perform {\em ab initio} density functional calculations to simulate scanning tunneling microscopy (STM) images of different layered allotropes of phosphorus and study the effect of capping layers on these images. We find that protective monolayers of insulating {\em h}-BN allow to distinguish between the different structural phases of phosphorus underneath, even though the images are filtered through only nitrogen atoms that appear transparent. No such distinction is possible for phosphorus films capped by semimetallic graphene that masks the underlying structure. Our results suggest that the real-space imaging capability of STM is not hindered by selected capping layers that protect phosphorus surfaces.