Improving endurance and spectral responses of protected telescope mirrors by implementing sputtering atomic layer augmented deposition (SALAD): Two case studies–silver and aluminum-based protected mirrors

The study explores the intricacies of crafting resilient broadband telescope mirrors, utilizing silver (Ag) and aluminum (Al). Ag-mirrors, renowned for exceptional reflectivity, demand protection from corrosion, necessitating coatings like aluminum oxide (AlOx). Similarly, Al-mirrors, effective in the far UV spectral range, require safeguarding due to Al's susceptibility to oxidation, employing coatings such as aluminum fluoride (AlFx). These scenarios emphasize the critical role played by the metal-dielectric interface (i.e., Ag/AlOx and Ag/AlFx) in achieving durable and high-performance mirrors. We currently use physical vapor deposition (PVD) and thermal atomic layer deposition (ALD) separately to fabricate these mirrors, leading to interface deterioration. The study proposes a solution using sputtering atomic layer augmented deposition (SALAD), seamlessly integrating PVD and ALD without breaking the vacuum. The study addresses multi-physics modeling, SALAD sample preparation, environmental testing, advanced characterization, and degradation mechanism assessment. By optimizing the metal-dielectric interface, aiming to enhance endurance and spectral responses of these mirrors.