Unraveling Metal-insulator Transition Mechanism of VO2Triggered by Tungsten Doping

Abstract

Understanding the mechanism of W-doping induced reduction of critical temperature (T_C) for VO₂ metal-insulator transition (MIT) is crucial for both fundamental study and technological application. Here, using synchrotron radiation X-ray absorption spectroscopy combined with first-principles calculations, we unveil the atomic structure evolutions of W dopant and its role in tailoring the T_C of VO₂ MIT. We find that the local structure around W atom is intrinsically symmetric with a tetragonal-like structure, exhibiting a concentration-dependent evolution involving the initial distortion, further repulsion, and final stabilization due to the strong interaction between doped W atoms and VO₂ lattices across the MIT. These results directly give the experimental evidence that the symmetric W core drives the detwisting of the nearby asymmetric monoclinic VO₂ lattice to form rutile-like VO₂ nuclei, and the propagations of these W-encampassed nuclei through the matrix lower the thermal energy barrier for phase transition.