The use of height tracking SECM to measure mechanically exfoliated graphite – Scanning Probes. Application Note 17.

Abstract

In this note, SECM is used in feedback mode to image the changes of conductivity of an exfoliated graphite sample deposited onto insulative substrate. dc-SECM was used in constant distance mode to avoid any damage to the fragile graphene layers by the tip. Topography measurements were performed using intermittent contact.

Introduction

At present, there is growing interest in 2D materials for both their practical and experimental applications. At the centre of this growing field is graphene, whose discovery was awarded the Nobel Prize in 2010 [1]. Exfoliated graphite is a precursor material to graphene and therefore it is of interest to fully understand its electrochemistry. Although SECM has previously been used to measure graphite in a variety of forms, much of this has focused on understanding its role as an electrode for Li batteries [2-4]. Recently, however, the electrochemical properties of graphene oxide have been measured using SECM by investigating its interaction with a variety of redox couples [5]. The electrochemical activity of graphene has also been measured by SECCM allowing the effects of the number of graphene layers and step edges to be examined [6, 7]. In this note, we present the use of the M470 to measure the electrochemical activity of mechanically exfoliated graphite using dc-SECM. On the scale of the SECM measurement mechanically exfoliated graphite is flat, however, sample tilt may result in the SECM probe touching the graphite flake. In the worst-case scenario this can fully remove the flake of interest. To ensure the graphite flake remained intact this measurement was performed using
a background topography map collected during an ic-SECM area scan, taken in an area adjacent to the graphite flake of interest, to perform a height tracking SECM measurement