*Phillip Rumsby, Bill Baloukas, Oleg Zabeida, Ludvik Martinu, Polytechnique de Montréal, Quebec, Canada
Thin silver films are gathering an increasing amount of interest as potential flexible transparent conductive electrodes, IR reflectors in low-emissivity windows, metasurfaces and many others. However, despite their promising optical and electronic properties, certain drawbacks inherent to the material limit their ease of use. Due to their high susceptibility to degradation by oxidation, corrosion and tarnishing, devices making use of silver layers require particular design considerations to withstand extended usage. Moreover, the deposition of highly transparent, ultra-thin continuous silver films has its own limitations imposed by their Volmer-Weber growth mode leading to island formation. In an attempt to conciliate these requirements, film growth and optical properties were investigated through in situ and ex situ ellipsometry, spectrophotometry and sheet resistance measurements. Silver degradation resistance was tested in various stack architectures by means of in situ spectrophotometry integrated with an accelerated corrosion testing cell. In addition, the degradation mechanism of tested films was studied using ex situ techniques including optical microscopy, scanning electron microscopy and sheath resistance measurements. The optical characterisation results are imported into a brute force algorithm which then allows us to optimize stack design following different figures of merit while maintaining the experimentally found constraints on minimum thickness of continuous silver layers and corrosion resistance. Following this method, optical coating architectures containing ultra-thin Ag films that are simultaneously highly transparent, conductive and environmentally resistant are produced.