Realizing Scalable Chemical Vapor Deposition of Monolayer Graphene Films on Iron with Concurrent Surface Hardening by In Situ Observations

TL;DR

Researchers developed a scalable method to grow high-quality graphene on iron while simultaneously hardening its surface, using in situ observations to understand the process.

Contribution

The study introduces a scalable CVD method for monolayer graphene on iron with concurrent surface hardening, enabled by in situ analysis of growth mechanisms.

Findings

In situ XRD and NAP XPS revealed that carbothermal reduction of Fe-oxides is critical for graphene growth on iron.

Carbon uptake during CVD near the Fe–C eutectoid enables surface hardening akin to carburization.

The process allows scalable, high-quality monolayer graphene growth on iron substrates.

Abstract

Graphene has been suggested as an ultimately thin functional
coating
for metallurgical alloys, such as steels. However, even on pure iron
(Fe), the parent phase of steels, the growth of high quality graphene
films remains largely elusive to date. We here report scalable chemical
vapor deposition (CVD) of high quality monolayer graphene films on
Fe substrates. To achieve this, we here elucidate the mechanisms of
graphene growth on Fe using complementary in situ X-ray diffractometry (XRD) and in situ near ambient
pressure X-ray photoelectron spectroscopy (NAP XPS) during our scalable CVD conditions. As key factors that set Fe apart from
other common graphene CVD catalyst supports such as Ni or Cu, we identify
that for Fe (i) carbothermal reduction of persistent Fe-oxides and
(ii) kinetic balancing of carbon uptake into the Fe during CVD near
the Fe–C eutectoid because of the complex multiphased Fe–C
phase diagram are critical. Additionally, we establish that the carbon
uptake into the Fe during graphene CVD is not only important in terms
of growth mechanism but can also be advantageously utilized for concurrent
surface hardening of the Fe during the graphene CVD process, akin
to carburization/case hardening. Our work thereby forms a framework
for controlled and scalable high-quality monolayer graphene film CVD
on Fe including the introduction of concurrent surface hardening during
graphene CVD.

Figures