Observation of low-wavenumber out-of-plane optical phonon in few-layer graphene

Authors

  • Jingzhi Shang,

    1. Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
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  • Chunxiao Cong,

    1. Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
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  • Jun Zhang,

    1. Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
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  • Qihua Xiong,

    1. Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
    2. Division of Microelectronics, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore
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  • Gagik G. Gurzadyan,

    Corresponding author
    • Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
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  • Ting Yu

    Corresponding author
    1. Division of Physcs and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
    2. Department of Physics, Faculty of Science, National University of Singapore, Singapore
    • Graphene Research Centre, National University of Singapore, Singapore
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Gagik G. Gurzadyan, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.

E-mail: gurzadyan@ntu.edu.sg

Ting Yu, Graphene Research Centre, National University of Singapore, 2 Science Drive 3, Singapore 117542.

E-mail: yuting@ntu.edu.sg

Abstract

Few-layer graphene grown by chemical vapor deposition has been studied by Raman and ultrafast laser spectroscopy. A low-wavenumber Raman peak of ~120 cm−1 and a phonon-induced oscillation in the kinetic curve of electron–phonon relaxation process have been observed, respectively. The Raman peak is assigned to the low-wavenumber out-of-plane optical mode in the few-layer graphene. The phonon band shows an asymmetric shape, a consequence of so-called Breit-Wigner-Fano resonance, resulting from the coupling between the low-wavenumber phonon and electron transitions. The obtained oscillation wavenumber from the kinetic curve is consistent with the detected low-wavenumber phonon by Raman scattering. The origin of this oscillation is attributed to the generation of coherent phonons and their interactions with photoinduced electrons. Copyright © 2012 John Wiley & Sons, Ltd.

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