Zero-Strain Metal-Insulator Transition by the Local Fluctuation of Cation Dimerization.

Park, Yunkyu; Sim, Hyeji; Lee, Sungwon; Park, Won-Woo; Hwang, Jaejin; Hur, Pyeongkang; Lee, Yujeong; Lee, Dong Kyu et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

The coupled electronic and structural transitions in metal-insulator transition (MIT) hinder ultrafast switching and ultimate endurance. Decoupling these transitions and achieving a zero-strain electronic MIT can overcome the fundamental limitations of MIT in solid materials. Here, this study demonstrates that iso-valent Ti dopants in supercooled VO<sub>2</sub> epitaxial films cause MIT with minimal hysteresis without changing unit-cell volume and crystal symmetry. The Ti dopants in the VO<sub>2</sub> lattice locally alter the configuration of V-V pairs, where the long-range ordering in V-V pairs is disrupted, and the nano-domains of V-V dimers are formed. Strikingly, these local V-V dimers persist even above the electronic transition temperature (T<sub>MI</sub>), facilitating the zero-strain electronic MIT with nanoscale structural heterogeneity. The geometrically compatible interface between insulating and metallic phases drastically enhances switching speed and endurance during electrically and optically driven zero-strain MIT. This discovery offers a fresh perspective on the scientific understanding of MIT and the improved functionality in terms of device speed and reliability by decoupling electronic and structural transitions.