▎ 摘　　要

Graphene was synthesized on a Cu film by chemical vapor deposition (CVD) and its grain size was analyzed by using dark-field transmission electron microscopy. The grain size was mainly controlled by changing the partial pressure of hydrocarbons in H-2/Ar. The grain size increased as the partial pressure of C2H4 decreased, but eventually leveled off. The size saturation may be related to the long growth time at a low partial pressure. It was also revealed that growth using CH4 provided graphene with larger grain sizes than that using C2H4 at the same partial pressure. Back-gate transistors were then fabricated using graphene with various grain sizes, and the dependence of field-effect mobility on the grain size was investigated. The mobility roughly scales with the grain size, but the intergrain angles and/or small holes at grain boundaries also seem to affect the carrier mobility. It was also found that low mobility was often caused by fractures and/or wrinkles in graphene channels. (C) 2013 The Japan Society of Applied Physics