Dominant Kinetic Pathways of Graphene Growth in Chemical Vapor Deposition: The Role of Hydrogen

TL;DR

This study uses multiscale simulations to reveal that hydrogen plays a stabilizing role in graphene growth during chemical vapor deposition, challenging previous assumptions about its etching effects.

Contribution

It uncovers the central role of hydrogen in stabilizing graphene edges and clarifies its dual role in growth and etching, aiding process optimization.

Findings

Hydrogen saturates graphene edges, depending on H₂ pressure.

Hydrogen reduces detachment rates of carbon species, stabilizing edges.

The new model explains experimental observations of hydrogen's role.

Abstract

The most popular way to produce graphene nowadays is chemical vapor deposition, where, surprisingly, H$_2$ gas is routinely supplied even though it is a byproduct itself. In this study, by identifying dominant growing pathways via multiscale simulations, we unambiguously reveal the central role hydrogen played in graphene growth. Hydrogen can saturate the edges of a growing graphene island to some extent, depending on the H$_2$ pressure. Although graphene etching by hydrogen has been observed in experiment, hydrogen saturation actually stabilizes graphene edges by reducing the detachment rates of carbon-contained species. Such a new picture well explains some puzzling experimental observations and is also instrumental in growth protocol optimization for two-dimensional atomic crystal van der Waals epitaxy.