Surface potential distribution of multilayer graphene using Kelvin probe and electric-field force microscopies

Surface properties of multilayer graphene (MLG) were studied by Kelvin Probe and Electric-field Force Microscopies (KPFM and EFM). Using KPFM, we observed an increase in the work function of MLG with increasing thickness. This is attributed to the surface π-electrons of p_z orbitals shifting the Fermi level away from the Dirac point. EFM measurements indicate that the EFM phase increases with DC electric fields (−5 V ≤ V ≤ 5 V) applied to the probe. The parabolic phase-shift dependence is pertaining to the electrostatic interaction produced at the tip-MLG interface. These results provide future directions in band-gap engineering of graphene-based devices.