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

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)CH_3(l) → HF + 2C_(s) + C₂F_(covalent) + CH₃C(O)CH_2(l). The fluorination and reduction processes permit the safe and facile non‐destructive property control of the s‐FG film.