Reversible hydrogenation and band gap opening of graphene and graphite surfaces probed by scanning tunneling spectroscopy

TL;DR

This study demonstrates that hydrogenation via plasma treatment opens a band gap in graphene and graphite surfaces, which can be partially reversed through thermal annealing, enabling reversible tuning of their electronic properties.

Contribution

It provides detailed scanning tunneling spectroscopy analysis showing reversible hydrogenation effects on the electronic properties of graphene and graphite surfaces.

Findings

Hydrogen chemisorption opens an average 0.4 eV band gap.

Surface topography changes are non-reversible, but electronic properties are reversible.

Samples can be hydrogenated multiple times with similar semiconducting behavior.

Abstract

The effect of hydrogenation on the topography and the electronic properties of graphene and graphite surfaces are studied by scanning tunneling microscopy and spectroscopy. The surfaces are chemically modified using Ar/H2 plasma. Analyzing thousands of scanning tunneling spectroscopy measurements we determine that the hydrogen chemisorption on the surface of graphite/graphene opens on average an energy band gap of 0.4 eV around the Fermi level. We find that although the plasma treatment modifies the surface topography in a non-reversible way, the change in the electronic properties can be reversed by a moderate thermal annealing and the samples can be hydrogenated again yielding a similar, but slightly reduced, semiconducting behavior after the second hydrogenation.