Controlling Surface Potential of Graphene Using dc Electric Field
In this work, we study surface potential of graphite deposited on SiO 2 /Si substrate using Kelvin Probe Force Microscopy (KPFM) and Electric Force Microscopy (EFM) The amplitude modulated KPFM (AM KPFM) shows that the graphene layer work function is 4.69+ 0.02 eV, whereas frequency modulated KPFM (FM KPFM) revealed 4.50+ 0.02 eV. The work function indifference of 0.19+ 0.02 eV was attributed to the superior resolution of FM KPFM and higher detection sensitivity of AM KPFM. Subsequent EFM mapping suggests that the phase monotonically increases with increasing applied dc bias voltage in the range from 5 V to 5 V. This phase shift is ascribed to the induced charge polarization at tip graphene surface due to interatomic interactions induced by dc field effects.