Insulator to metal transition of WO3 epitaxial films induced by electrochemical Li-ion intercalation

TL;DR

This study explores how electrochemical Li-ion intercalation induces an insulator to metal transition in WO3 epitaxial films, revealing phase coexistence and the critical Li content for conductivity change.

Contribution

It demonstrates controlled Li-ion intercalation in WO3 films and correlates phase coexistence with the insulator-metal transition, advancing understanding of electrochemical tuning of electronic properties.

Findings

Resistivity drops abruptly at x ~ 0.2-0.24

IMT coincides with cubic NaxWO3 behavior

Phase coexistence observed during IMT

Abstract

We investigated systematic evolutions of structural and electronic properties of LixWO3 films, induced by Li-ion electrochemical reactions. Chronoamperometric Li-ion intercalation could control the amount of Li content up to x ~ 0.5. The resistivity abruptly decreased with increasing x and the films underwent an insulator to metal transition (IMT) within a range of 0.2 < x < 0.24, which was consistent with IMT of cubic NaxWO3. The X-ray diffraction analyses revealed the coexistence of tetragonal and cubic phases across IMT, suggesting that the alkaline-ion content was a primary factor for metallic conductivity in the ReO3-type WO3 system.