Reflectance changes of Fe and Cr doped Ag thin films deposited by magnetron sputtering

Silver-based highly-reflective coatings are extensively used in the optoelectronic devices. However, it is still difficult to accomplish both high reflectivity and long-term stability of the protected silver-based reflectors simultaneously. In this report, we have investigated the optical properties of sputter deposited FeCr-doped Silver alloy thin films on glass substrates at room temperature. We observed that the alloying FeCr with silver can significantly improve the silver surface morphology while keeping its reflectance same as that of pure silver in the near-infrared region of the electromagnetic spectrum. However, at the same time, in the visible region about 400 nm of the wavelength, the reflectance was decreased by increasing the FeCr content. The less amount of FeCr-doped silver films exhibited high reflectivity as similar to that of pure silver. In this study, we have interpreted the simple model describing the trend of the reflectance of silver-alloy films due to FeCr-doping. We also investigated the thermal stability of the pure silver and FeCr-doped silver films and the corresponding thermally induced grain growth results revealed that, the FeCr-doping is effective to restrain the severe grain growth of silver films.