# Characterization of Hydrogen Plasma Defined Graphene Edges

## TL;DR

This study characterizes hydrogen plasma etched graphene edges, revealing their predominantly zigzag nature with some armchair segments, and highlights the need for process optimization to achieve pure crystalline edges.

## Contribution

It provides detailed analysis of hydrogen plasma etching effects on graphene edges using multiple techniques, showing the edges are mixed and not yet ideal.

## Key findings

- Hexagonal etch pits reflect anisotropic etching.
- Edges are mainly zigzag but contain armchair segments.
- Electronic transport indicates high bulk quality but lower edge quality.

## Abstract

We investigate the quality of hydrogen plasma defined graphene edges by Raman spectroscopy, atomic resolution AFM and low temperature electronic transport measurements. The exposure of graphite samples to a remote hydrogen plasma leads to the formation of hexagonal shaped etch pits, reflecting the anisotropy of the etch. Atomic resolution AFM reveals that the sides of these hexagons are oriented along the zigzag direction of the graphite crystal lattice and the absence of the D-peak in the Raman spectrum indicates that the edges are high quality zigzag edges. In a second step of the experiment, we investigate hexagon edges created in single layer graphene on hexagonal boron nitride and find a substantial D-peak intensity. Polarization dependent Raman measurements reveal that hydrogen plasma defined edges consist of a mixture of zigzag and armchair segments. Furthermore, electronic transport measurements were performed on hydrogen plasma defined graphene nanoribbons which indicate a high quality of the bulk but a relatively low edge quality, in agreement with the Raman data. These findings are supported by tight-binding transport simulations. Hence, further optimization of the hydrogen plasma etching technique is required to obtain pure crystalline graphene edges.