Searching for refractory plasmonic materials: the structural and optical properties of Au$_{3}$Zr intermetallic thin films.

Optical properties of refractory intermetallic thin films of Au$_{3}$Zr were experimentally investigated for the first time, which show distinctive plasmonic properties in the visible and near infrared region. The films were fabricated through DC magnetron sputtering at various deposition temperature ranging from room temperature to 427$^{o}$C and annealed at different vacuum levels. Both the structural and optical properties are found to be critically dependent on deposition temperature and anneal conditions. Films deposited between 205-320$^{o}$C are shown to exhibit lower negative permittivity and better thermal stability, which could be linked to specific crystalline orientations. The films are stable when annealed at 10$^{-8}$ Torr, but are partially oxidized when annealed at 10$^{-6}$ Torr, suggesting oxidization could be a restricting issue for high-temperature applications in ambient environment.