| Summary: | Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001. === Cataloged from PDF version of thesis. === Includes bibliographical references (page 23). === The purpose of this work is to characterize the optical absorption in bismuth silicon oxide (Bi₁₂SiO₂₀) crystals grown using the Bridgman technique and to identify electronic transitions responsible for absorption. Optical measurements were taken in the range of 0.4 - 11 pm at 300 K and 77 K using a spectrometer. The results show that near the band edge, there is evidence of indirect transitions at 2.3 eV and excition transitions at 1.8 eV. Low temperature measurements revealed peaks of free carrier absorption in the visible light range at 1.7 eV and 2.1 eV. Illuminated samples at low temperature revealed empty donor levels in the visible range at 1.6-1.9 eV and 2.1 eV, indicating the presence of the photochromic effect and photorefractivity. === by Grace W. Lee. === S.B.
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