Properties of chemical-vapor-deposited silicon carbide for optics applications in severe environments

Important data on chemical-vapor-deposited (CVD) SiC concerning the elastic modulus, polishability, scattering measurement, thermal and cryogenic stability, and degradation owing to the effects of atomic oxygen and electron beams have been obtained with the aim of assessing the suitability of SiC as an optical substrate for severe environments. These measurements show that CVD SiC substrates exhibit excellent polishability (<0.1 nm rms) with low scatter, good retention of mechanical properties up to 1500 degrees C, superior thermal and cryogenic stability (-190 degrees to 1350 degrees C) and high resistance to atomic-oxygen and electron-beam degradation. These results suggest that CVD SiC optical substrates will perform extremely well in severe environments such as outer space, and when used in lasers, combustion, and synchrotron x rays.