Local transport measurements at mesoscopic length scales using scanning tunneling potentiometry

TL;DR

This paper demonstrates the use of scanning tunneling potentiometry to measure spatial variations in transport potential at mesoscopic scales in epitaxial graphene, revealing quantum interference effects and defect-related features.

Contribution

First detailed measurement of mesoscopic transport potential variations using scanning tunneling potentiometry on epitaxial graphene at low temperature.

Findings

Observation of residual resistivity dipoles near defects

Detection of local potential peaks and dips unrelated to topography

Mitigation of tip jumping artifacts with custom-made tips

Abstract

Under mesoscopic conditions, the transport potential on a thin film with current is theoretically expected to bear spatial variation due to quantum interference. Scanning tunneling potentiometry is the ideal tool to investigate such variation, by virtue of its high spatial resolution. We report in this {\it Letter} the first detailed measurement of transport potential under mesoscopic conditions. Epitaxial graphene at a temperature of 17K was chosen as the initial system for study because the characteristic transport length scales in this material are relatively large. Tip jumping artifacts are a major possible contribution to systematic errors; and we mitigate such problems by using custom-made slender and sharp tips manufactured by focussed ion beam. In our data, we observe residual resistivity dipoles associated with topoographical defects, and local peaks and dips in the potential that are not associated with topographical defects.