Description: 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.

Benefits: The ultimate goal of this research is to make silicon clad mirrors for lightweight telescopes. NASA applications include future UVOIR space-based observatories, cryogenic IR mirrors, high-frequency RF reflectors operating above 100-GHz, and laser scanning and relay mirrors.

Non NASA applications include lightweight mirrors for missile interceptor telescopes (Missile Defense Agency), high-energy laser mirrors (US Air Force), space-based RF reflectors for high-frequency communication (about 100 GHz) (US Air Force). If low enough prices can be achieved by coating large volumes of small mirrors, high-performance laboratory grade mirrors could be sold through distributers such as "Edmond Scientific" and others.