Thermal Evaporation Enhanced Atomic Layer Deposition for Far Ultraviolet Mirror Coatings and Bandpass Filters

Dr. Robin Rodriguez, JPL Postdoctoral Fellow

Thursday, December 15 @ 11:00 am (PT) via WebEx

Abstract: Aluminum is the only reflective metal that offers broad ultraviolet/visible/near-infrared response, making it highly relevant for use in all far ultraviolet (FUV, 90-200 nm) optical systems. However, aluminum is very reactive and susceptible to oxidation, which can limit its performance in the FUV. Metal-fluoride coatings like MgF2, LiF, and AlF3 are UV-transparent materials that can protect aluminum against oxidation, which is key to achieving the desired optical properties in the FUV. Therefore, it is desirable to protect the aluminum surface before it can oxidize. We report on the development of a custom, JPL-built, thin film deposition reactor capable of doing physical vapor deposition (PVD) of aluminum by thermal evaporation, and atomic layer deposition (ALD) of metal-fluorides in the same vacuum system. Sequentially combining both deposition techniques without breaking vacuum could enhance the performance of UV instruments that utilize aluminum. We also report on the development of FUV bandpass metal-dielectric filters (MDFs) and UV mirror coatings using the processes mentioned above. MDFs were fabricated on Si charge coupled devices (CCDs, by Teledyne e2v) that will be used in the FUV channel of the Star-Planet Activity Research CubeSat (SPARCS). Similar MDFs will be directly integrated on SRI complementary metal-oxide-semiconductor (CMOS) detectors for the Ultraviolet Explorer’s (UVEX’s) FUV channel. Lastly, ultra-thin ALD MgF2 coatings were deposited on LiF-coated Al mirrors that will be used in the Supernova remnants and Proxies for Reionization Integrated Testbed Experiment (SPRITE) CubeSat. This MgF2 capping layer provides the mirror with enhanced environmental stability and negligible reflectance losses. This same MgF2 capping layer will be used on LiF-coated Al mirrors for an Astrophysics Pioneers mission called Aspera.

About the speaker: Robin Rodríguez is a JPL Postdoctoral Fellow in the Advanced Detectors and Nanomaterials group of the Microdevice and Sensor Systems section. He completed a BS in Mechanical Engineering from the University of Puerto Rico, Mayagüez in 2015 and an MSE and PhD in Mechanical Engineering at the University of Michigan in 2021. During his PhD studies, Robin designed and built an atomic layer deposition (ALD) reactor for thin film processing. At JPL, Robin has been working on updating and automating a JPL-built, custom, thermal evaporation enhanced atomic layer deposition (TE-ALD) reactor that will enable aluminum and metal-fluoride deposition processes within the same vacuum system. He is also using his expertise in thin film coating processes and characterization techniques to study and develop filter coatings and protective mirror coatings for advanced far ultraviolet (FUV) detectors and aluminum mirrors, respectively.

WebEx Info:
Meeting number (access code): 2763 392 4743
Meeting password: Gt5a29VwkWF

12/15/2022 - 11:00
Dr. Robin Rodriguez, JPL Postdoctoral Fellow