Phonon and plasmon excitation in inelastic electron tunneling spectroscopy of graphite

TL;DR

This study uses scanning tunneling spectroscopy at low temperature to analyze phonon and plasmon excitations in graphite, revealing detailed vibrational and electronic surface phenomena with theoretical and experimental agreement.

Contribution

It provides the first demonstration of local surface-plasmon excitation detection in graphite via IETS and discusses phonon mode enhancement mechanisms.

Findings

Spectral features match vibrational density of states from first principles

Identification of surface-plasmon excitation at 40 meV

Enhanced phonon modes due to phonon-assisted tunneling

Abstract

The inelastic electron tunneling spectrum (IETS)of highly oriented pyrolitic graphite (HOPG) has been measured with scanning tunneling spectroscopy (STS) at 6K. The observed spectral features are in very good agreement with the vibrational density of states (vDOS) of graphite calculated from first principles. We discuss the enhancement of certain phonon modes by phonon-assisted tunneling in STS based on the restrictions imposed by the electronic structure of graphite. We also demonstrate for the first time the local excitation of surface-plasmons in IETS which are detected at an energy of 40 meV.