Effect of deposition conditions on the response and durability of an Mg4Ni film switchable mirror

We are developing switchable mirror thin films based on an Mg-Ni alloy which can be switched between mirror and transparent states. The Mg4Ni alloy thin film was prepared on a glass substrate by DC magnetron co-sputtering of Mg and Ni targets and was subsequently covered in situ with a thin layer of Pd. The interface structure between Pd and Mg-Ni layers was found to have a crucial effect on the switching response and durability. By controlling the sputtering sequence and tailoring the interface structure, the switching response can be improved by 50-80% for the dehydrogenation process. The switching durability of the improved thin film is twice as long as that of a typical sample. We have also found that the switching response is dependent on the substrate temperature during sputtering. The dehydrogenation rate can be increased when the substrate is retained below room temperature.