The field effect behavior of graphene films in air and vacuum

In the present study, the field effect behavior of graphene films grown in a home-built CVD system was analyzed by fabricating graphene field effect transistor (GFET). Under the electrostatic effect of applied gate voltage, graphene films showed unipolar behavior (p-type) in transfer characteristics when the device is kept in air. A unipolar to bipolar conversion was observed with GFET transfer characteristics while performing measurements in vacuum. The decreased electron-hole symmetry was observed and it is a deviation from ideal characteristics. The hole mobility was 510 cm2V-1s−1 for measurements carried out in air. Later, with ambipolar behavior, the films showed a hole mobility of 455 cm2V-1s−1 and an electron mobility of 143 cm2V−1s-1.