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

We investigated the systematic evolution of the structural and electronic properties of Lix WO₃ films induced by Li-ion electrochemical reactions. Chronoamperometric Li-ion intercalation could control the Li content up to x > 0.5. The resistivity decreased abruptly 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 the IMT of cubic NaxWO₃. X-ray diffraction analyses revealed the coexistence of tetragonal and cubic phases across the IMT, suggesting that the alkaline ion content was the primary factor in the metallic conductivity of the ReO3-type WO₃ system.