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ABSTRACT
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 pz 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.
Funding
This work is supported by the Foundation for Science and Technology of Portugal, grants SFRH/BPD/104887/2014 (RV) and SFRH/BPD/88362/2012 (KR). KR and ALK are grateful to the Russian Foundation for Basic Research (grant No. 16-29-14050-ofr-m) and Government of the Russian Federation (Act 211, Agreement 02.A03.21.0006) for the financial support. Part of this work was developed in the scope of Project CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and, when applicable, cofinanced by FEDER under the PT2020 Partnership Agreement.