Characterization of AlF3-passivated aluminum mirrors using non-contact thermal metrology

We demonstrate the use of steady-state thermoreflectance (SSTR) as a technique for characterizing mirror surfaces. Due to the enhanced sensitivity of thermoreflectance compared to reflectance, SSTR provides the ability to assess the physical and chemical characteristics as well as the uniformity of thin films and coatings much more rapidly than common metrological methods such as x-ray photoelectron spectroscopy. The use of this technique is demonstrated on AlF3-passivated Al surfaces produced using a process developed for the fabrication of far ultraviolet reflectors. However, since SSTR is thermal in nature, this technique negates the need for a priori knowledge of the optical properties of the material. This is emphasized by interrogating both homogeneous and non-uniform AlF3 films.