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en 1987 Ward Lewis Johnson ultrasonic waves point defects in crystals electron-irradiated P-type silicon An ultrasonic study of point defects in electron-irradiated P-type silicon Dissertation / Thesis text Granato, A.V. Johnson, Ward Lewis 2011-06-02T16:48:07Z 2011-06-02T16:48:07Z 10000-01-01 1987 The mechanisms of interaction of ultrasonic waves with point defects in crystals are reviewed and a perturbation approach is introduced which leads to general expressions for the resonance and relaxation strengths in terms of matrix elements of the ultrasonic perturbation. These expressions provide the basis for a discussion of the polarization dependence of resonance and relaxation. Selection rules for cubic crystals are presented. An exploratory ultrasonic study is performed on electron-irradiated Bdoped and Al-doped silicon. Neutral substitutional boron is detected before irradiation, as expected from previous ultrasonic studies on unirradiated silicon. This defect produces both resonance and relaxation. Similar effects are observed for substitutional aluminum. After irradiation, a relaxation is observed when the sample is exposed to 0.18-0.39 eV light. By comparison with previous EPR results, this relaxation is identified as the singly positively charged state of the vacancy, v+. Preliminary results on the relaxation time and strength of v+ suggest that it may have several populated vibronic levels. Another relaxation is observed in irradiated Al-doped silicon when the sample is exposed to white light. From its annealing behavior and dopant dependence, we identify it as a non-equilibrium charge state of interstitial aluminum. The most likely states appear to be Ali 0 and Ali-. Analysis of the polarization dependence of the relaxation leads to the conclusion that the aluminum atom rests at a Td interstitial site and the surrounding lattice is Jahn-Teller distorted with e-type (tetragonal or <100> orthorhombic) symmetry. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-02T16:48:07Z No. of bitstreams: 1 1987_Johnson.pdf: 2194738 bytes, checksum: dcf1616b18341b11851e0b9d2b9c92d4 (MD5) Made available in DSpace on 2011-06-02T16:48:07Z (GMT). No. of bitstreams: 1 1987_Johnson.pdf: 2194738 bytes, checksum: dcf1616b18341b11851e0b9d2b9c92d4 (MD5) Previous issue date: 1987 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-02T16:48:07Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:12:41-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 1411696 http://hdl.handle.net/2142/25224 University of Illinois at Urbana-Champaign Physics Physics Dissertation Ph.D.