Optical property and cycling durability of polytetrafluoroethylene top-covered and metal buffer layer inserted Mg–Ni switchable mirror

Pd-capped Mg-rich Mg–Ni alloy thin film shows excellent reversible switching properties in optical transmittance by the exposure to hydrogen containing gas. However, it shows fast degradation due to the oxidization of magnesium and the switching durability is not good enough for practical applications. To resolve this problem we tried to improve its switching durability of Mg–Ni based switchable mirror by the combined use of metal buffer layer insertion between Pd and Mg–Ni layer and polytetrafluoroethylene (PTFE) protective coating. PTFE thin film has been prepared on the surface of Mg–Ni thin films by RF magnetron sputtering in the Ar and CF4 mixed gas discharge plasma at room temperature and a power of 30 W. The sample of Pd/Ti/Mg4Ni thin film with the protective coating of 900-nm-thick PTFE layer can be switched over 1600 switching cycles, which suppress the degradation by 15% of its initial transmission modulation level.