Investigation of surface potentials in reduced graphene oxide flake by Kelvin probe force microscopy

Abstract

The surface potential (SP) of reduced graphene oxide (rGO) flakes prepared by thermal treatments of GO under several conditions was analyzed by Kelvin probe force microscopy. The low-crystalline rGO flakes in which a significant amount of oxygen functional groups and structural defects remain have a much lower SP than mechanically exfoliated graphene free from oxygen and defects. On the other hand, the highly crystalline rGO flake after a thermal treatment for the efficient removal of oxygen functional groups and healing of structural defects except for domain boundary shows SP equivalent to that of the mechanically exfoliated graphene. These results indicate that the work function of rGO is sensitively modulated by oxygen functional groups and structural defects remaining after the thermal reduction process, but is not affected significantly by the domain boundary remaining after the healing of structural defects through the thermal treatment at high temperature.

Kelvin probe force microscopic investigation of graphene-based derivatives

“…Ethanol assisted annealing involves in the recovery of graphitic structure by repairing the lattice defects. We also demonstrate the layer dependence on WF of CVD-grown 21) 4.56 GO-EtOH-1000 °C 4.95 GO-750 °C 5.91 Mechanically exfoliated graphene 28) 4.92 CVD graphene 22) 4.50 Mechanically exfoliated graphene 23) 4.57 4.69 Mechanically exfoliated graphene 20) 5.11 Epitaxial graphene 12) 4.55 4.44 graphene. We anticipate that the reported CPD and WF values in this work can assist in studying and optimizing the electrical properties of graphene-based derivatives for further analyses.…”

Customizing the reduction of individual graphene oxide flakes for precise work function tuning with meV precision

“…In KPFM measurements, the SP is known to be linked to WF based on the following relation: 35 ϕ s = ϕ tip − eV CPD ϕ s and ϕ tip is the WF of the sample and the KPFM tip, respectively. V CPD refers to the measured SP.…”