Hydrogenating VO2 with protons in acid solution

TL;DR

This paper presents a simple, cost-effective method to hydrogenate VO2 using metal-assisted proton doping in acid solution, inducing insulator-metal transitions and enabling large-area doping.

Contribution

It introduces a novel metal-acid co-doping technique for VO2 that prevents lattice corrosion and achieves large-area hydrogenation through a ripple effect.

Findings

Achieved insulator-to-metal transition in VO2 via proton doping.

Demonstrated large-area doping (>2 inch) triggered by tiny metal particles.

Proposed a cost-effective alternative to traditional hydrogenation methods.

Abstract

Hydrogenation is an effective way to tune material property1-5. Traditional techniques for doping hydrogen atoms into solid materials are very costly due to the need for noble metal catalysis and high-temperature/pressure annealing treatment or even high energy proton implantation in vacuum condition5-8. Acid solution contains plenty of freely-wandering protons, but it is difficult to act as a proton source for doping, since the protons always cause corrosions by destroying solid lattices before residing into them. Here we achieve a facile way to hydrogenate monoclinic vanadium dioxide (VO2) with protons in acid solution by attaching suitable metal to it. Considering the Schottky contact at the metal/VO2 interface, electrons flow from metal to VO2 due to workfunction difference and simultaneously attract free protons in acid solution to penetrate, forming the hydrogens dopants inside VO2 lattice. This metal-acid treatment constitutes an electron-proton co-doping strategy, which not only protects the VO2 lattice from corrosion, but also causes pronounced insulator-to-metal transitions. In addition, the metal-acid induced hydrogen doping behavior shows a ripple effect, and it can spread contagiously up to wafer-size area (>2 inch) even triggered by a tiny metal particle attachment (~1.0mm). This will stimulate a new way of simple and cost-effective atomic doping technique for some other oxide materials.