Nanoscale Thermal Imaging of VO$_2$ via Poole-Frenkel Conduction

TL;DR

This paper introduces a nanoscale thermal imaging method using AFM and Poole-Frenkel conduction modeling to measure local temperatures in insulating thin films with high spatial resolution, applicable to various insulators.

Contribution

The authors develop a novel AFM-based thermometry technique leveraging Poole-Frenkel conduction to achieve nanoscale temperature mapping of insulating films.

Findings

Achieved spatial resolution better than 50 nm.

Demonstrated method on VO$_2$ thin films.

Applicable to any insulator with Poole-Frenkel conduction.

Abstract

We present a method for nanoscale thermal imaging of insulating thin films using atomic force microscopy (AFM), and we demonstrate its utility on VO$_2$. We sweep the applied voltage $V$ to a conducting AFM tip in contact mode and measure the local current $I$ through the film. By fitting the $IV$ curves to a Poole-Frenkel conduction model at low $V$, we calculate the local temperature with spatial resolution better than 50 nm using only fundamental constants and known film properties. Our thermometry technique enables local temperature measurement of \textit{any} insulating film dominated by the Poole-Frenkel conduction mechanism, and can be extended to insulators that display other conduction mechanisms.