Direct mapping of electronic orbitals in graphene using electron energy-loss spectroscopy

TL;DR

This paper demonstrates how electron energy-loss spectroscopy can directly visualize electronic orbitals in graphene, revealing spatial distributions of unoccupied states and highlighting the technique's potential for studying material properties.

Contribution

It introduces a method to map electronic orbitals in graphene using EELS and validates it with simulations, emphasizing the impact of material thickness on resolution.

Findings

Spatial mapping of $\pi^ ext{*}$ and $\sigma^ ext{*}$ states in graphene

Validation of EELS signals with inelastic channeling simulations

Thickness-dependent resolution of unoccupied states

Abstract

The spatial distributions of anti-bonding $\pi^\ast$ and $\sigma^\ast$ states in epitaxial graphene multilayers are mapped using electron energy-loss spectroscopy in a scanning transmission electron microscope. Inelastic channeling simulations validate the interpretation of the spatially-resolved signals in terms of electronic orbitals, and demonstrate the crucial effect of the material thickness on the experimental capability to resolve the distribution of unoccupied states. This work illustrates the current potential of core-level electron energy-loss spectroscopy towards the direct visualization of electronic orbitals in a wide range of materials, of huge interest to better understand chemical bonding among many other properties at interfaces and defects in solids.