Revealing the role of high-valence elementary substitution in the hydrogen-induced Mottronic transitions of vanadium dioxide

Electron-doping Mottronics within correlated vanadium dioxide (e.g., VO2) opens up a paradigm to abruptly regulate the Mottronic phase transitions via adjusting the d-orbital occupancy and configuration. Nevertheless, the potential impact of high-valence elementary substitution in the hydrogen-associated Mottronic transitions of VO2 is yet unclear. Herein, we demonstrate the role of high-valence elementary substitution (e.g., W6+) in regulating the hydrogen-triggered Mottronic transitions of VO2, assisted by quantitative hydrogen analysis using the nuclear reaction analysis. Substituting vanadium with a high-valence transitional metal (e.g., W6+) within doped-VO2 largely reduces the hydrogen incorporation (e.g., ∼1.61 × 1021 cm−3 in H0.06V0.95W0.05O2) compared to the intrinsic VO2 (e.g., ∼1.08 × 1022 cm−3 in H0.35VO2) under the low temperature hydrogenation process. Therefore, in contrast to hydrogen-induced electron localization of intrinsic VO2 upon low-temperature hydrogenation, only the hydrogen-triggered metallic state is observed within the hydrogen-associated phase diagram of WxV1-xO2, as further probed by the near-edge x-ray absorption fine structure analysis and x-ray photoelectron spectroscopy. The present work reveals the overlooked role associated with the donor substitutions that largely influences the competitive equilibrium between the two rival hydrogen-induced Mottronic transitions within VO2 toward either the metallic or the highly insulating phase.