Surface Metal-Insulator Transition on a Vanadium Pentoxide (001) Single Crystal

In situ band gap mapping of the V₂O₅(001) crystal surface revealed a reversible metal-to-insulator transition at 350–400 K, which occurs inhomogeneously across the surface and expands preferentially in the direction of the vanadyl (V=O) double rows. Supported by density functional theory and Monte Carlo simulations, the results are rationalized on the basis of the anisotropic growth of vanadyl-oxygen vacancies and a concomitant oxygen loss driven metal-to-insulator transition at the surface. At elevated temperatures irreversible surface reduction proceeds sequentially as V₂O₅(001)→V₆O₁₃(001)→V₂O₃(0001).