Optical, structural, and functional properties of highly reflective and stable iridium mirror coatings for infrared applications

Iridium (Ir) provides a high and broadband intrinsic reflectivity from the mid to far-infrared spectral range. In contrast to well-established (protected) mirror coatings of silver and gold, Ir thin films are environmentally durable, referring to ISO 9211 3 and thermally stable up to 600°C even without protective layers, as demonstrated. Additionally, the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI, AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings differ significantly due to their different topography and microstructure.