Zone-resolved photoelectronic scoping of the local bonding and electronic dynamics at the graphite skin with and without atomic vacancy and the associated graphene edge states

TL;DR

This study uses zone-resolved photoelectron spectroscopy to analyze local bonding and electronic dynamics at graphite surfaces, revealing how atomic vacancies and edges influence electronic states and bonding characteristics.

Contribution

It provides the first experimental confirmation of how atomic vacancies and edges affect bonding and electronic states in graphite using ZPS combined with STM/STS and DFT.

Findings

Surface bonds contract by 18% with increased energy

Defect bonds are ~26% shorter and 215% stronger

Vacancies induce polarization peaks and Dirac-Fermi polarons

Abstract

A zone-resolved photoelectron spectroscopy (ZPS) has enabled us to gain the local and quantitative information and hence confirm our theoretical expectations on the bonding and electronic dynamics at graphite skin with and without atomic vacancy defects. The ZPS study has revealed: i) the 1s energy level of an isolated carbon atom is located at 282.57 eV, which shifts by 1.32 eV deeper upon diamond bulk formation; ii) the graphite surface bonds contract by 18% with 165% gain in energy compared with the C-C bond in the bulk diamond; the surface C 1s energy shifts 2.08 eV deeper from the 1s level of an isolated carbon atom; and iii) the defect bonds are ~26% shorter and 215% stronger with the binding energy shift of ~2.85 eV. An additional polarization peak centered at 1.28 eV below the C 1s level presents when the vacancy is formed. Associated with the scanning tunneling microscopy/spectroscopy observations and density functional theory calculations, the ZPS measurements clarify, for the first time, that the graphitic Dirac-Fermi polarons at atomic vacancy or graphene zigzag edge arise from the polarization of the unpaired dangling-bond electrons by the undercoordination-induced local densification and quantum entrapment of the bonding electrons.