The evolution of surface cleanness and electronic properties of graphene field-effect transistors during mechanical cleaning with atomic force microscopy

The evolution of surface cleanliness and the electronic properties-Dirac voltage(V-D(irac)), hysteresis and mobility (mu) of a graphene field-effect transistor (GFET)-were monitored by measuring lateral force microscopy and drain current (I-D) as a function of gate voltage (V-G), after mechanically cleaning the surface, scan-by-scan, with contact-mode atomic force microscopy. Both the surface cleanliness and the electronic properties evolved, showing a sudden improvement and then saturation for a mobility of around 2200 cm(2) V-1 s(-1). We found that the mobility suppression of the as-fabricated GFET deviated from a randomly distributed impurities model, which predicted a greater mobility than obtained from the measured V-D(irac). Therefore, the substrate impurities are excluded from the origins of the extraordinary suppression of the mobility, and the possible origin will be discussed.