Crystalline hydrogenation of graphene by STM tip-induced field dissociation of H$_2$

TL;DR

This paper introduces a nanoscale method for crystalline hydrogenation of graphene using STM tip-induced dissociation of H₂, enabling precise control over hydrogen coverage and reversible modifications.

Contribution

The study demonstrates a novel STM-based technique for controlled, reversible crystalline hydrogenation of graphene at the nanoscale, including the formation of specific superstructures.

Findings

Achieved localized hydrogenation of graphene using STM tip-induced dissociation.

Formed various ordered hydrogenated phases, including a crystalline rac{3}{ ext{}} imes rac{3}{ ext{}} R30b0 phase.

Reversible hydrogenation demonstrated by imaging at higher bias voltages.

Abstract

We have developed a novel method for crystalline hydrogenation of graphene on the nanoscale. Molecular hydrogen was physisorbed at 5 K onto pristine graphene islands grown on Cu(111) in ultrahigh vacuum. Field emission local to the tip of a scanning tunneling microscope dissociates H$_2$ and results in hydrogenated graphene. At lower coverage, isolated point defects are found on the graphene and are attributed to chemisorbed H on top and bottom surfaces. Repeated H$_2$ exposure and field emission yielded patches and then complete coverage of a crystalline $\sqrt{3}$ $\times$ $\sqrt{3}$ R30{\deg} phase, as well as less densely packed 3 $\times$ 3 and 4 $\times$ 4 structures. The hydrogenation can be reversed by imaging with higher bias voltage.