Birefringence measurements, using a scanning infra-red polariscope with high sensitivity, were carried out in as-grown dislocation-free Si single crystal ingots. A small amount of birefringence due to <110> optical anisotropy, which was predicted not by the classical optics theory but by the Lorentz's spatial dispersion theory, was observed in the θ¯Z optical configuration, for which a probing polarized light was introduced from the as-grown cylindrical ingot surface and then the polarization of the light transmitted through the opposite surface was analyzed. On the other hand, in the R¯θ optical configuration, for which the probing polarized light was introduced along the <001> crystal growth direction from the (001) sliced and polished surface and then the polarization of the light transmitted through the opposite (001) surface was analyzed, the birefringence was still observed although it was extremely small. It was found that this <001> optical anisotropy was not constant over the (001) cross-section of the ingot but consists of two different components, i.e. a symmetric component distributed over the whole sample, probably caused by point defects, and an asymmetric component distributed randomly near the peripheral region, related to dents and chips on the as-grown cylindrical surface.

Optical Anisotropy and Strain-Induced Birefringence in Dislocation-Free Silicon Single Crystals. T.Chu, M.Yamada, J.Donecker, M.Rossberg, V.Alex, H.Riemann: Materials Science and Engineering B, 2002, 91-92, 174-7