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Keywords:

  • graphene;
  • semi-ionic fluorination;
  • transition from insulator to graphene;
  • covalent C-F bond;
  • ionic C-F bond;
  • add-atom engineering

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) [RIGHTWARDS ARROW] 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.