Conductivity landscape of highly oriented pyrolytic graphite surface containing ribbons and edges

TL;DR

This study investigates the electrical properties of graphene ribbons and edges on HOPG using AFM, revealing complex conductance variations influenced by layer displacement, edge structure, and local charge distribution.

Contribution

It provides detailed insights into how shear forces and step edges affect the electrical conductance of graphite surfaces, highlighting the heterogeneity of conductive behavior.

Findings

Top layer exhibits higher conductance than lower layers.

Different ribbons on the same sheet show varying conductance.

Edges can show sharp increases in current, with some areas showing dips or absence of such features.

Abstract

We present an extensive study on electrical spectroscopy of graphene ribbons and edges of highly oriented pyrolytic graphite (HOPG) using atomic force microscope (AFM). We have addressed in the present study two main issues, (1) How does the electrical property of the graphite (graphene) sheet change when the graphite layer is displaced by shear forces? and (2) How does the electrical property of the graphite sheet change across a step edge? While addressing these two issues we observed, (1) variation of conductance among the graphite ribbons on the surface of HOPG. The top layer always exhibits more conductance than the lower layers, (2) two different monolayer ribbons on the same sheet of graphite shows different conductance, (3) certain ribbon/sheet edges show sharp rise in current, (4) certain ribbons/sheets on the same edge shows both presence and absense of the sharp rise in the current, (5) some lower layers at the interface near a step edge shows a strange dip in the current/conductance (depletion of charge). We discuss possible reasons for such rich conducting landscape on the surface of graphite.