Carbon Impurities on Graphene Synthesized by Chemical Vapor Deposition on Platinum

TL;DR

This study reveals the presence of nanocrystalline carbon impurities in CVD-grown graphene on platinum, affecting optical and microscopic characterization but not significantly impairing electrical mobility.

Contribution

It uncovers the coexistence of carbon impurities with graphene on platinum and highlights the limitations of Raman spectroscopy in assessing electronic quality.

Findings

Nanocrystalline carbon impurities coexist with graphene.

Impurity island orientation depends on platinum's crystalline orientation.

High electrical mobility (~6,000 cm2/Vs) despite impurities.

Abstract

We report nanocrystalline carbon impurities coexisting with graphene synthesized via chemical vapor deposition (CVD) on platinum. We observe micron-size island-like impurity layers, which can easily be mistaken for second graphene layers in optical microscopy or secondary electron microscopy (SEM). The island orientation depends on the crystalline orientation of the Pt, as shown by electron backscatter diffraction(EBSD), indicating growth of amorphous carbon below graphene. Dark-field TEM indicates that in addition to uniform single-crystal graphene, our sample is decorated with nanocrystalline carbon impurities with a spatially inhomogeneous distribution. Raman spectra show a large D peak, however electrical characterization shows high mobility (~6,000 cm2/Vs), indicating a limitation for Raman spectroscopy in characterizing the electronic quality of graphene.