Dehydrogenation process of Mg–Ni based switchable mirrors analyzed by in situ spectroscopic ellipsometry

The dehydrogenation process of hydrogenated switchable mirrors using magnesium–nickel alloy thin film was studied in situ using spectroscopic ellipsometry. Ellipsometric angles Ψ and Δ of the switchable mirrors varied drastically as a result of dehydrogenation, which is a transformation from transparent to reflective states. The process was analyzed by dividing into the following three phases. The first phase was the dehydrogenation process of a thin Mg4Ni layer with several nanometers at a hydrogenated Pd/Mg4Ni interface. The second phase was the dehydrogenation processes of the hydrogenated Mg4Ni layer, which proceeded from the Pd/Mg4Ni interface to the substrate. The final phase was the desorption process of hydrogen, which was absorbed in Mg4Ni as solid solution and the dehydrogenation process was terminated.

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► Dehydrogenation process of Mg4Ni switchable mirrors was revealed by ellipsometry.
► Dehydrogenation proceeded from the Pd/Mg4Ni interface to the substrate.
► Origin of the black state was clarified.