Temperature dependence of Mott transition in VO_2 and programmable critical temperature sensor

TL;DR

This study investigates the temperature-dependent Mott transition in VO_2 devices, revealing a phase between the Mott transition and structural phase transition, and demonstrates the device's potential as a programmable critical temperature sensor.

Contribution

It uncovers a monoclinic correlated metal phase in VO_2 and demonstrates a VO_2-based device as a programmable critical temperature sensor.

Findings

Abrupt current jump at MIT with temperature

Transition temperature decreases with higher voltage

Uniform current flow during MIT

Abstract

The temperature dependence of the Mott metal-insulator transition (MIT) is studied with a VO_2-based two-terminal device. When a constant voltage is applied to the device, an abrupt current jump is observed with temperature. With increasing applied voltages, the transition temperature of the MIT current jump decreases. We find a monoclinic and electronically correlated metal (MCM) phase between the abrupt current jump and the structural phase transition (SPT). After the transition from insulator to metal, a linear increase in current (or conductivity) is shown with temperature until the current becomes a constant maximum value above T_{SPT}=68^oC. The SPT is confirmed by micro-Raman spectroscopy measurements. Optical microscopy analysis reveals the absence of the local current path in micro scale in the VO_2 device. The current uniformly flows throughout the surface of the VO_2 film when the MIT occurs. This device can be used as a programmable critical temperature sensor.