Graphene, often hailed as “the wonder material of the 21st century,” can revolutionize various industries due to its exceptional properties, including ultra-high electrical conductivity and remarkable tensile strength. However, a major obstacle to its widespread use has been its susceptibility to impurities.
A team of engineers from Columbia University, in collaboration with researchers from the University of Montreal and the National Institute of Standards and Technology, has developed an oxygen-free chemical vapor deposition (OF-CVD) method. This groundbreaking technique enables the large-scale production of high-quality graphene, addressing the longstanding issue of graphene impurities.
Published in Nature, this breakthrough not only enhances the reproducibility of graphene production but also promises to expand its practical applications in various industries, from electronics to biomedicine.
“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.”
Graphene has historically been synthesized using two methods. The first method, the “scotch-tape” method, involves peeling individual layers from a bulk sample of graphite using household tape. This results in clean, impurity-free samples ideal for lab research. However, these samples are too small—just a few tens of micrometers across—for industrial-scale applications.
About 15 years ago, researchers developed a method to synthesize large-area graphene, known as CVD growth, to move from lab explorations to real-world applications. This process allows for the synthesis of large-area graphene by passing a carbon-containing gas, such as methane, over a copper surface at high temperatures, resulting in the formation of a single layer of graphene. Despite extensive research efforts to scale up this method, CVD-synthesized samples have faced challenges with reproducibility and quality consistency.
The presence of oxygen has been identified as a significant issue. Previous research by co-authors Richard Martel and Pierre Levesque demonstrated that even trace amounts of oxygen can hinder the growth process and cause degradation of graphene.
To address this, Christopher DiMarco, GSAS’19, developed a CVD growth system that allows precise control over the introduction of oxygen during deposition. This work was further advanced by current PhD students Xingzhou Yan and Jacob Amontree, who managed to enhance the growth system and eliminate trace oxygen.
As a result, they observed significantly faster CVD growth with consistent outcomes. Additionally, their study of oxygen-free CVD graphene growth kinetics led to the development of a simple model that accurately predicts growth rate across various parameters such as gas pressure and temperature.
The samples grown using the OF-CVD method demonstrated a quality virtually indistinguishable from that of exfoliated graphene. Working with colleagues in Columbia’s physics department, their graphene exhibited compelling evidence of the fractional quantum Hall effect under magnetic fields, a quantum phenomenon previously observed only in ultrahigh-quality, two-dimensional electrical systems.
Next, the team aims to devise a method for seamlessly transferring the high-quality graphene from the metal growth catalyst to other functional substrates, such as silicon. This final step will enable us to fully harness the potential of this wonder material.
“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.”
Journal reference:
- Jacob Amontree, Xingzhou Yan, Christopher S. DiMarco, Pierre L. Levesque, Tehseen Adel, Jordan Pack, Madisen Holbrook, Christian Cupo, Zhiying Wang, Dihao Sun, Adam J. Biacchi, Charlezetta E. Wilson-Stokes, Kenji Watanabe, Takashi Taniguchi, Cory R. Dean, Angela R. Hight Walker, Katayun Barmak, Richard Martel & James Hone. Reproducible graphene synthesis by oxygen-free chemical vapour deposition. Nature, 2024; DOI: 10.1038/s41586-024-07454-5