Electronic transition from graphite to graphene via controlled movement of the top layer with scanning tunneling microscopy

TL;DR

This study demonstrates controlled electronic and structural transitions in graphite to graphene using electrostatic manipulation with STM, revealing tunable symmetry changes and layer displacements validated by DFT calculations.

Contribution

It introduces a method to reversibly and irreversibly control the top layer of graphite, enabling systematic study of the transition to graphene at atomic resolution.

Findings

Reversible and irreversible layer movements observed

Transition from triangular to hexagonal symmetry controlled

DFT confirms vertical and horizontal layer displacements

Abstract

A series of measurements using a technique called electrostatic-manipulation scanning tunneling microscopy (EM-STM) were performed on a highly-oriented pyrolytic graphite surface. The electrostatic interaction between the STM tip and the sample can be tuned to produce both reversible and irreversible large-scale movement of the graphite surface. Under this influence, atomic-resolution STM images reveal that a continuous electronic transition from triangular symmetry, where only alternate atoms are imaged, to hexagonal symmetry can be systematically controlled. Density functional theory (DFT) calculations reveal that this transition can be related to vertical displacements of the top layer of graphite relative to the bulk. Evidence for horizontal shifts in the top layer of graphite is also presented. Excellent agreement is found between experimental STM images and those simulated using DFT.