▎ 摘　　要

A simple method was found to observe the semiconducting behavior of graphene using the O-2 gas adsorption property. Graphene was synthesized by thermal chemical vapor deposition with NH3 as the nitrogen doping source. The current response increased significantly when the p-type graphene was exposed to an O-2 environment. The current response decreased gradually when the nitrogen content was increased. When the NH3 flow rate was increased to 80 sccm during graphene synthesis, the p-type graphene becomes n-type and the nitrogen-doped graphene current response clearly decreases during O-2 gas adsorption measurements. We measured the graphene Dirac point using a field-effect transistor to define the graphene semiconducting properties. These results show that gas adsorption measurements can reveal the graphene semiconducting performance and also the n-type graphene synthesis conditions. (C) 2014 The Japan Society of Applied Physics