Quantifying Joule heating in voltage-biased VO₂ thin films using atomic force microscopy

Vanadium dioxide (VO₂) undergoes a thermally-driven insulator-to-metal transition (IMT) when heated above 341 K, making it a promising material for oxide electronic applications. The IMT has also been observed in voltage-biased films as a sharp jump in the measured current when the voltage is increased. The roles of Joule heating, electric field effects, and charge injection in the IMT are poorly understood and actively studied.

Here we first use an atomic force microscope (AFM) in contact mode to map the local current response of voltage-biased polycrystalline VO₂ thin films. We fit the I-V curve to the temperature-dependent Poole-Frenkel conduction mechanism and calculate the local temperature of the film to be 337 K immediately preceding the transition, confirming the role of Joule heating.¹

Secondly, we use non-contact AFM (nc-AFM), in which an oscillating sensor detects the local force and power dissipation between the tip and VO₂ film sample. As we ramp the sample bias, we observe a rise and subsequent drop in the power dissipated, indicating the film has switched to the metallic state. Our pre-transition dissipation curve fits well to Joule heating, suggesting a temperature-triggered IMT.

¹ Spitzig et al. APL 120, 151602 (2022)