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Property Control of Graphene by Employing “Semi-Ionic” Liquid Fluorination

Authors

  • Jong Hak Lee,

    1. SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea
    2. Department of Physics, National University of Singapore, 117542, Singapore
    3. Graphene Research Center, National University of Singapore, 117542, Singapore
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  • Gavin Kok Wai Koon,

    1. Department of Physics, National University of Singapore, 117542, Singapore
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  • Dong Wook Shin,

    1. SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea
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  • V. E. Fedorov,

    1. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences 3, Acad. Lavrentiev prospect, Novosibirsk, 630090, Russia
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  • Jae-Young Choi,

    1. Samsung Advanced Institute of Technology, Yongin, Gyeonggi, 446-712, Republic of Korea
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  • Ji-Beom Yoo,

    Corresponding author
    1. SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea
    2. School of Advanced Materials Science & Engineering (BK21), Sungkyunkwan University, Suwon 440-746, Republic of Korea
    • SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea
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  • Barbaros Özyilmaz

    Corresponding author
    1. Department of Physics, National University of Singapore, 117542, Singapore
    2. Graphene Research Center, National University of Singapore, 117542, Singapore
    3. NanoCore, National University of Singapore, 117576, Singapore
    4. NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, 117456, Singapore
    • Department of Physics, National University of Singapore, 117542, Singapore.
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Abstract

Semi-ionically fluorinated graphene (s-FG) is synthesized with a one step liquid fluorination treatment. The s-FG consists of two different types of bonds, namely a covalent C-F bond and an ionic C-F bond. Control is achieved over the properties of s-FG by selectively eliminating ionic C-F bonds from the as prepared s-FG film which is highly insulating (current < 10−13 A at 1 V). After selective elimination of ionic C-F bonds by acetone treatment, s-FG recovers the highly conductive property of graphene. A 109 times increase in current from 10−13 to 10−4A at 1 V is achieved, which indicates that s-FG recovers its conducting property. The properties of reduced s-FG vary according to the number of layers and the single layer reduced s-FG has mobility of more than 6000 cm2 V−1 s−1. The mobility drastically decreases with increasing number of layers. The bi-layered s-FG has a mobility of 141cm2 V−1 s−1 and multi-layered s-FG film showed highly p-type doped electrical property without Dirac point. The reduction via acetone proceeds as 2C2F(semi-ionic) + CH3C(O)CH3(l) → HF + 2C(s) + C2F(covalent) + CH3C(O)CH2(l). The fluorination and reduction processes permit the safe and facile non-destructive property control of the s-FG film.

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