Atomic-resolution structural and spectroscopic evidence for the synthetic realization of two-dimensional copper boride

TL;DR

This study provides atomic-resolution structural and spectroscopic evidence for the synthesis of a two-dimensional copper boride, expanding the understanding of 2D metal boride materials and their electronic properties.

Contribution

It demonstrates the first atomic-scale characterization of 2D copper boride grown on Cu(111), revealing unique electronic states and covalent bonding distinct from borophene.

Findings

FER spectroscopy shows unique charge transfer states

STM and DFT confirm atomic structure of Cu8B14

Evidence suggests strong covalent bonding in 2D copper boride

Abstract

Since the first realization of borophene on Ag(111), two-dimensional (2D) boron nanomaterials have attracted significant interest due to their polymorphic diversity and potential for hosting solid-state quantum phenomena. Here, we use atomic-resolution scanning tunneling microscopy (STM) and field-emission resonance (FER) spectroscopy to elucidate the structure and properties of atomically thin boron phases grown on Cu(111). Specifically, FER spectroscopy reveals unique charge transfer and electronic states compared to the distinct borophene phases observed on silver, suggesting that the deposition of boron on copper can result in strong covalent bonding characteristic of a 2D copper boride. This conclusion is reinforced by detailed STM characterization of line defects that are consistent with density functional theory (DFT) calculations for atomically thin Cu8B14. This evidence for 2D copper boride is likely to motivate future synthetic efforts aimed at expanding the relatively unexplored family of atomically thin metal boride materials.