high infrared, vapor deposition, molybdenum films, photothermal conversion


High infrared reflectance, coupled with higher solar absorptance, is required for efficient photothermal conversion. Converters can be fabricated by depositing an absorber on a highly reflecting metal. The absorber functions in the visible, yet becomes transparent in the near infrared, allowing the metal to suppress the thermal emittance. Economic considerations demand the use of thin films, rather than bulk materials. The thin film reflector must be capable of withstanding high temperatures of operation. Compatibility of the reflector with the substrate below, and the absorber above, is required for long-time service. Highly reflective silver films suffer reflectance losses by agglomeration, and require stabilization layers. Refractory materials such as molybdenum avoid agglomeration at temperatures of operation of photothermal converters. Unlike other deposition methods, chemical vapor deposition (CVD) can produce molybdenum films with an infrared reflectance rivaling that of bulk molybdenum. CVD is a non-vacuum based technology with potential for sequential through-put fabrication. Studies are being undertaken to determine how sensitively the reflectance reacts to inclusions of impurities into the molybdenum. Thin film passivators deposited on the molybdenum prevent reflectance losses induced by oxidation, and insure high temperature survival of optimal reflectance. Complete converter stacks have been annealed at 550 °C for over 1000 hours in air.

Original Publication Citation

G.E. Carver, David D. Allred, and B.O. Seraphin, "Chemical Vapor Deposited Molybdenum for Use in Photothermal Conversion," Optics Applied to Solar Energy IV, Proceedings of SPIE 161, 66 71 (1978).

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Peer-Reviewed Article

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Society of Photo Optical Instrumentation Engineers (SPIE)




Physical and Mathematical Sciences


Physics and Astronomy