Abstract
Chemical vapour deposition of carbon-containing precursors on metal substrates is currently the most promising route for the scalable synthesis of large-area, high-quality graphene films1. However, there are usually some imperfections present in the resulting films: grain boundaries, regions with additional layers (adlayers), and wrinkles or folds, all of which can degrade the performance of graphene in various applications2,3,4,5,6,7. There have been numerous studies on ways to eliminate grain boundaries8,9 and adlayers10,11,12, but graphene folds have been less investigated. Here we explore the wrinkling/folding process for graphene films grown from an ethylene precursor on single-crystal Cu–Ni(111) foils. We identify a critical growth temperature (1,030 kelvin) above which folds will naturally form during the subsequent cooling process. Specifically, the compressive stress that builds up owing to thermal contraction during cooling is released by the abrupt onset of step bunching in the foil at about 1,030 kelvin, triggering the formation of graphene folds perpendicular to the step edge direction. By restricting the initial growth temperature to between 1,000 kelvin and 1,030 kelvin, we can produce large areas of single-crystal monolayer graphene films that are high-quality and fold-free. The resulting films show highly uniform transport properties: field-effect transistors prepared from these films exhibit average room-temperature carrier mobilities of around (7.0 ± 1.0) × 103 centimetres squared per volt per second for both holes and electrons. The process is also scalable, permitting simultaneous growth of graphene of the same quality on multiple foils stacked in parallel. After electrochemical transfer of the graphene films from the foils, the foils themselves can be reused essentially indefinitely for further graphene growth.
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Data availability
The data sets generated during the current study, and/or analysed during the current study, are available from the corresponding author upon reasonable request.
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Acknowledgements
This work was supported by the Institute for Basic Science (IBS-R019-D1). We appreciate discussions with R. Huang (UT Austin) and K. Duck Park and H. Lee of UNIST.
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R.S.R., D.L. and Meihui Wang conceived the experiments. R.S.R. supervised the project. Meihui Wang did CVD growths. Meihui Wang and D.L. characterized films. S.J., Y.K. and M.K. prepared Cu(111) foils. M.H. and Mengran Wang prepared Cu–Ni(111) alloy foils. Y.L. made and tested the GFET devices. M.C., S.C. and Z.L. acquired and analysed TEM/SAED data. W.S. measured the LEED patterns and analysed the high-temperature XRD data (acquired by staff member M. J. Woo of the Korea Advanced Institute of Science and Technology (KAIST)). W.S. designed, built and tested the 6-inch CVD system which is now used by Meihui Wang and others. Meihui Wang wrote a draft manuscript and R.S.R., Meihui Wang and D.L. revised it. All co-authors commented on the manuscript prior to its submission.
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The Institute for Basic Science has filed a patent application (KR 10-2021-0095514) that lists Meihui Wang, D.L. and R.S.R. as inventors. Other than this, the authors declare no competing interests.
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Wang, M., Huang, M., Luo, D. et al. Single-crystal, large-area, fold-free monolayer graphene. Nature 596, 519–524 (2021). https://doi.org/10.1038/s41586-021-03753-3
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DOI: https://doi.org/10.1038/s41586-021-03753-3
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