Reversible and non-volatile metal-to-insulator chemical transition in molybdenum oxide films

Significant effort is being dedicated to developing alternative materials whose optical properties can be controllably and reversibly modified. Here, we experimentally demonstrate the reversible non-volatile molybdenum oxides MoO₃-to-MoO₂ transition associated to a change from a metallic to a dielectric behavior through cycles of thermal annealing in air and hydrogen (H₂). A full cycle is demonstrated by characterizing structurally and optically the transition using Raman spectroscopy and spectroscopic ellipsometry. The potential applicability of the metal-to-insulator transition in MoO_x is benchmarked through comparison with a canonical Mott insulator VO₂ in a reconfigurable reflective configuration as well as in cladded waveguide schemes.