Electron–Proton Co‐doping‐Induced Metal–Insulator Transition in VO₂ Film via Surface Self‐Assembled <scp>l</scp>‐Ascorbic Acid Molecules

Abstract

Abstract Charge doping is an effective way to induce the metal–insulator transition (MIT) in correlated materials for many important utilizations, which is however practically limited by problem of low stability. An electron–proton co‐doping mechanism is used to achieve pronounced phase modulation of monoclinic vanadium dioxide (VO 2 ) at room temperature. Using l ‐ascorbic acid (AA) solution to treat VO 2 , the ionized AA − species donate electrons to the adsorbed VO 2 surface. Charges then electrostatically attract surrounding protons to penetrate, and eventually results in stable hydrogen‐doped metallic VO 2 . The variations of electronic structures, especially the electron occupancy of V 3d/O 2p hybrid orbitals, were examined by synchrotron characterizations and first‐principle theoretical simulations. The adsorbed molecules protect hydrogen dopants from escaping out of lattice and thereby stabilize the metallic phase for VO 2 .