Microscopy of hydrogen and hydrogen-vacancy defect structures on graphene devices

TL;DR

This study uses STM to analyze hydrogen defect structures on graphene, revealing how different hydrogen configurations affect electronic properties and opening new conductance channels.

Contribution

It identifies and characterizes two distinct hydrogen defect types on graphene supported by h-BN using STM and first-principles calculations.

Findings

Hydrogen vacancies bonded to graphene are created by ion bombardment.

Atomic hydrogen deposition forms dimerized hydrogen defects.

Dimerized hydrogen defects introduce new elastic tunneling channels.

Abstract

We have used scanning tunneling microscopy (STM) to investigate two types of hydrogen defect structures on monolayer graphene supported by hexagonal boron nitride (h-BN) in a gated field-effect transistor configuration. The first H-defect type is created by bombarding graphene with 1-keV ionized hydrogen and is identified as two hydrogen atoms bonded to a graphene vacancy via comparison of experimental data to first-principles calculations. The second type of H defect is identified as dimerized hydrogen and is created by depositing atomic hydrogen having only thermal energy onto a graphene surface. Scanning tunneling spectroscopy (STS) measurements reveal that hydrogen dimers formed in this way open a new elastic channel in the tunneling conductance between an STM tip and graphene.