Low-Stress Silicon Cladding for Surface Finishing Large UVOIR Mirrors, Phase I

Metadata Updated: May 2, 2019

In this Phase I research, ZeCoat Corporation will develop an affordable, low-stress silicon cladding process which is super-polishable for large UVOIR mirrors. The proposed ion-assisted evaporation process is directly scaleable to SiC mirrors several meters in diameter. The process is based on a novel, low temperature, ion-assisted, evaporation technique (IAD), whereby the coating stress of a silicon film may be manipulated from compressive to tensile, in order to produce a near-zero net stress for the complete layer. A cladding with little intrinsic stress is essential to minimize bending that would otherwise distort the figure of very lightweight mirrors.
Current methods to produce a polishable silicon cladding utilize CVD processes that produce highly stressed Si coatings. The current processes require high-temperatures (hundreds of degrees Celsius) and are not readily scaleable to large mirrors. CVD Si cladding is currently limited to mirror substrates less than 1-meter in diameter. The proposed IAD process produces little heat, and the mirror size is limited only by the size of the vacuum chamber. Large silicon carbide (SiC) mirrors (3-4 meters in diameter) are being considered for future space-based UVOIR astronomy missions. These lightweight mirrors will likely require a highly-polishable layer of silicon (10 to 50 microns) applied on top of the SiC. A relatively thick layer of Si is desirable for the purpose of reducing figuring time and for achieving a super-polished surface, suitable for UV astronomy. Normal incidence 4-meter class UVOIR telescopes have been cited as a high priority by multiple government review panels including; the National Research Council's (NRC) study of NASA's Space Technology Roadmap and Priorities, The Office of the Chief Technologist, The Cosmic Origins Program and NWNH Decadal.

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Metadata Created Date August 1, 2018
Metadata Updated Date May 2, 2019

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Harvested from NASA Data.json

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Resource Type Dataset
Metadata Created Date August 1, 2018
Metadata Updated Date May 2, 2019
Publisher Space Technology Mission Directorate
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Maintainer Email
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Harvest Source Title NASA Data.json
Data First Published 2013-11-01
Homepage URL https://techport.nasa.gov/view/16654
License http://www.usa.gov/publicdomain/label/1.0/
Data Last Modified 2018-07-19
Program Code 026:027
Source Datajson Identifier True
Source Hash 0ee415f86c07bf8509eaee58247d917be95e3488
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