The pesky poly(methyl methacrylate) (PMMA) residues left from transferring graphene grown by chemical vapour deposition (CVD) have remained a challenge for maximising this potentially scalable approach to high-quality graphene production. Now researchers at West Virginia University have demonstrated a simple electrolytic cleaning method for removing PMMA residues that greatly reduces impairments to the electronic properties caused by these contaminants.
A widely adopted approach to removing PMMA after its use to transfer CVD graphene from its growth substrate is thermal annealing. However the residues left by this approach have been linked to p-doping and reduced carrier mobility in the resulting graphene film.
Jianbo Sun, Harry O Finklea and Yuxin Liu first investigated the contaminants in PMMA-transferred CVD graphene using Raman spectroscopy after annealing at temperatures between 100 °C and 500 °C. They identified that the residues were conjugated unsaturated carbon systems left behind as the methoxycarbonyl side chain of PMMA was heated off.
They then demonstrated that they could remove these residues using a cathodic electrolytic cell in an approach similar to methods for cleaning rust from iron and other conducting surfaces. Gas bubbles released during the electrolysis stripped the residues from the graphene surface. They then tested the graphene in simple field effect transistor devices and found the electronic properties greatly restored.
Publication Journal:“Characterization and electrolytic cleaning of poly(methyl methacrylate) residues on transferred chemical vapor deposited graphene”, Jianbo Sun et al. Published 23 February 2017 • © 2017 IOP Publishing Ltd, Nanotechnology, Volume 28, Number 12
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