▎ 摘　　要

Transport characteristics of graphene field-effect transistors were measured in situ in oxygen/nitrogen atmospheres and at various temperatures. Mobilities of holes were extracted from transport characteristics as well as the doping level depending on the time of graphene exposure to oxygen/nitrogen atmosphere. The hole mobility showed significant decrease upon the oxygen adsorption to low energy adsorption sites (sp(2) carbon); however, it remained unaffected by the oxygen adsorption to high-energy adsorption sites which are represented by defects, impurities, transfer residuals, edges, and functional groups on graphene. The Dirac point was upshifted for both the low- and high-energy adsorption events. Activation energy of oxygen adsorption/desorption was estimated from temperature-dependent desorption rate coefficients as 215 and 450 meV for the low- and high-energy adsorption sites, respectively.