On the mechanisms of precipitation of graphene on nickel thin films

TL;DR

This paper investigates the detailed mechanisms of graphene precipitation on nickel thin films, focusing on carbon dissolution and diffusion processes using ion implantation, annealing, and electron microscopy.

Contribution

It provides new insights into the microscopic mechanisms of graphene formation on nickel, highlighting the roles of carbon diffusion and multiple precipitation pathways.

Findings

Carbon dissolves into nickel via ion implantation.

Graphene precipitation involves long-range carbon diffusion.

Multiple microscopic mechanisms are involved in precipitation.

Abstract

Growth on transition metal substrates is becoming a method of choice to prepare large-area graphene foils. In the case of nickel, where carbon has a significant solubility, such a growth process includes at least two elementary steps: (1) carbon dissolution into the metal, and (2) graphene precipitation at the surface. Here, we dissolve calibrated amounts of carbon in nickel films, using carbon ion implantation, and annealing at 725 \circ or 900 \circ. We then use transmission electron microscopy to analyse the precipitation process in detail: the latter appears to imply carbon diffusion over large distances and at least two distinct microscopic mechanisms.