The Hone lab at Columbia Engineering created over 100 identical graphene samples with their oxygen-free chemical vapor deposition method.
Researchers have developed a high-quality graphene sample by eliminating virtually all oxygen from the growth process. Graphene, which offers ultra-high electrical conductivity, has the potential to transform electronics, energy storage, sensors, biomedical devices, and more.
Engineers at Columbia University and colleagues at the University of Montreal and the National Institute of Standards and Technology used an oxygen-free chemical vapor deposition (OF-CVD) method to develop high-quality graphene samples.
“We show that eliminating virtually all oxygen from the growth process is the key to achieving reproducible, high-quality CVD graphene synthesis,” said senior author James Hone, Wang Fong-Jen Professor of Mechanical Engineering at Columbia Engineering. “This is a milestone towards large-scale production of graphene.”
Trace oxygen affects the growth rate of graphene
Their work, published on May 29 in Nature, directly demonstrates how trace oxygen affects the growth rate of graphene and identifies the link between oxygen and graphene quality for the first time.
Graphene has historically been synthesized in one of two ways. There’s the “scotch-tape” method, in which individual layers are peeled from a bulk sample of graphite (the same material you’ll find in pencil lead) using household tape.
Such exfoliated samples can be quite clean and free from impurities that would otherwise interfere with graphene’s desirable properties.
However, they tend to be too small—just a few tens of micrometers across–for industrial-scale applications and, thus, better suited for lab research.
To move from lab explorations to real-world applications, researchers developed a method to synthesize large-area graphene about 15 years ago.
This process, known as CVD growth, passes a carbon-containing gas, such as methane, over a copper surface at a temperature high enough (about 1000 °C) that the methane breaks apart and the carbon atoms rearrange to form a single honeycomb-shaped layer of graphene.
CVD growth can be scaled up to create graphene samples that are centimeters or even meters in size. However, despite years of effort from research groups around the world, CVD-synthesized samples have suffered from problems with reproducibility and variable quality.
The issue was oxygen. In prior publications, co-authors Richard Martel and Pierre Levesque from Montreal had shown that trace amounts of oxygen can slow the growth process and even etch the graphene away.
So, about six years ago, Christopher DiMarco, GSAS’19, designed and built a CVD growth system in which the amount of oxygen introduced during the deposition process could be carefully controlled.
Trace oxygen was eliminated
Current PhD students Xingzhou Yan and Jacob Amontree found that when trace oxygen was eliminated, CVD growth was much faster—and gave the same results every time.
They also studied the kinetics of oxygen-free CVD graphene growth and found that a simple model could predict growth rate over a range of different parameters, including gas pressure and temperature.
“We both became fascinated by graphene and its potential as undergraduates,” Amontree and Yan said. “We conducted countless experiments and synthesized thousands of samples over the past four years of our PhDs. Seeing this study finally come to fruition is a dream come true.”
Team to develop a method to cleanly transfer their high-quality graphene to other functional substrates such as silicon.
The quality of the OF-CVD-grown samples proved virtually identical to that of exfoliated graphene. In collaboration with colleagues in Columbia’s physics department, their graphene displayed striking evidence for the fractional quantum Hall effect under magnetic fields, a quantum phenomenon that had previously only been observed in ultrahigh-quality, two-dimensional electrical systems.
From here, the team plans to develop a method to cleanly transfer their high-quality graphene from the metal growth catalyst to other functional substrates such as silicon — the final piece of the puzzle to take full advantage of this wonder material.
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Prabhat Ranjan Mishra Prabhat, an alumnus of the Indian Institute of Mass Communication, is a tech and defense journalist. While he enjoys writing on modern weapons and emerging tech, he has also reported on global politics and business. He has been previously associated with well-known media houses, including the International Business Times (Singapore Edition) and ANI.
