[20p-221B-1~11] 4.5 Nanocarbon and 2D Materials

▲ [20p-221B-7] [INVITED] Oxygen/Water Redox Couple Governing Charge Transfer Doping of 2D Materials

〇Sunmin Ryu¹, Kwanghee Park¹, Haneul Kang¹ (1.POSTECH)

Keywords:charge transfer doping, graphene, Raman spectroscopy

Low dimensional carbon materials in the ambient conditions undergo spontaneous hole doping, the detailed mechanism of which has yet to be revealed. In this work, we propose a mechanism based on a redox couple of O₂/H₂O and verified it for two model systems: i) thermally-induced charge transfer (TICT) of graphene/SiO₂ in air and ii) acid-induced charge transfer (AICT) of graphene/SiO₂ in water. Raman spectroscopy and water contact angle measurements were used to quantify the charge density in graphene and hydrophilicity of substrates, respectively. First, it will be shown that TICT is regulated by competition between thermal hydroxylation and dehydroxylation of SiO₂ surface. While the former fueled by interfacial water was dominant for annealing temperature of 200 ~ 700 ^oC inducing hole doping, the latter prevailed at 700 ~ 1000 ^oC undoing hole doping. Second, it will be shown that graphene in acidic solution is hole-doped and the charge transfer requires dissolved oxygen. The proposed mechanism will be discussed to explain the ambient hole doping of single layer WS₂.