Imaging Electrical Conduction through InAs Nanowires

TL;DR

This paper demonstrates how a scanning probe microscope can spatially image and analyze electron flow and quantum dot behavior in InAs nanowires at low temperatures, revealing complex Coulomb blockade phenomena.

Contribution

It introduces a method to use an SPM tip as a movable gate to image conductance and locate quantum dots within InAs nanowires, providing new insights into their local electronic properties.

Findings

Imaging of conductance maps quantum dot locations.

Identification of multiple quantum dots along nanowires.

Observation of Coulomb blockade interference patterns.

Abstract

We show how a scanning probe microscope (SPM) can be used to image electron flow through InAs nanowires, elucidating the physics of nanowire devices on a local scale. A charged SPM tip is used as a movable gate. Images of nanowire conductance vs. tip position spatially map the conductance of InAs nanowires at liquid He temperatures. Plots of conductance vs. back gate voltage without the tip present show complex patterns of Coulomb-blockade peaks. Images of nanowire conductance identify multiple quantum dots located along the nanowire - each dot is surrounded by a series of concentric rings corresponding to Coulomb blockade peaks. An image locates the dots and provides information about their size. The rings around individual dots interfere with each other like Coulomb blockade peaks of multiple quantum dots in series. In this way, the SPM tip can probe complex multi-dot systems by tuning the charge state of individual dots. The nanowires were grown from metal catalyst particles and have diameters ~ 80 nm and lengths 2 to 3 um.