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by Lui Kai Man, Raymond. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 221-225). / Acknow1edgements / Abstract --- p.i / Table of Contents --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Sample Preparation --- p.12 / Chapter A. --- Introduction --- p.12 / Chapter B. --- The Working Systems --- p.12 / Chapter C. --- Sample Preparation --- p.14 / Chapter C.1 --- The Method Of Reactive Evaporation --- p.14 / Chapter C.2 --- The Method Of Posthydrogenation --- p.15 / Chapter D. --- The Substrates --- p.16 / Chapter Chapter 3 --- "Electrical Conductivities, Thermal and Optical Stability Experiments" --- p.21 / Chapter A. --- Introduction --- p.21 / Chapter B. --- Theory --- p.22 / Chapter B.1 --- Electronic Transport In Amorphous Semiconductor --- p.22 / Chapter B.2 --- dc Electrical Conductivity in Davis-Mott Model --- p.23 / Chapter B.3 --- Photoconductivity --- p.27 / Chapter B.4 --- Staebler-Wronski Effect --- p.28 / Chapter C. --- Experimental Method --- p.29 / Chapter C.1 --- Dark And Photo Conductivities Measurements --- p.29 / Chapter C.2 --- Optical Stability Measurement --- p.32 / Chapter C.3 --- Thermal Stability Measurement --- p.32 / Chapter D. --- Results --- p.34 / Chapter D.1 --- Reactively Evaporated Samples --- p.34 / Chapter D.2 --- Temperature Dependence Of Conductivities --- p.34 / Chapter D.3 --- Optical Stability Measurement --- p.35 / Chapter D.4 --- Thermal Stability Measurement --- p.36 / Chapter E. --- Discussions --- p.36 / Chapter E.1 --- Electrical Properties Of Reactively Evaporated a-Si:H --- p.36 / Chapter E.2 --- A Comparative Study Between Reactive Evaporated Samples With Those From Other Reactive Deposition Techniques And Glow-Discharge Process --- p.37 / Chapter F. --- Conclusions --- p.38 / Chapter Chapter 4 --- Infrared Absorption Experiment --- p.63 / Chapter A. --- Introduction --- p.63 / Chapter A.1 --- General Description --- p.63 / Chapter A.2 --- Types Of Atomic Vibrations --- p.64 / Chapter A.3 --- Infrared Spectroscopy Of a-Si:H --- p.64 / Chapter A.4 --- Effect Of Substrate Temperature On Bonding Configuration --- p.65 / Chapter B. --- Experimental Method --- p.66 / Chapter C. --- Results --- p.66 / Chapter D. --- Discussions --- p.67 / Chapter D.1 --- Identification Of The Two Absorption Bands --- p.67 / Chapter D.2 --- Effect Of Substrate Temperature --- p.68 / Chapter E. --- Conclusions --- p.70 / Chapter Chapter 5 --- Electron Spin Resonance Experiment --- p.82 / Chapter A. --- Introduction --- p.82 / Chapter B. --- Theory --- p.85 / Chapter B. 1 --- The Absorption Process --- p.85 / Chapter B. 2 --- The Relaxation Process --- p.86 / Chapter C. --- Experimental Method --- p.90 / Chapter D. --- Results --- p.92 / Chapter E. --- Discussions --- p.93 / Chapter F. --- Conclusions --- p.96 / Chapter Chapter 6 --- Optical Absorption Experiment --- p.114 / Chapter A. --- Introduction --- p.114 / Chapter B. --- Theory On Optical Transitions Within Amorphous Materials --- p.114 / Chapter B.1 --- General Descriptions --- p.114 / Chapter B.2 --- Band Models For Optical Absorptions In An Amorphous Semiconductor --- p.116 / Chapter C. --- Experimental Method --- p.121 / Chapter E. --- Analysis --- p.123 / Chapter E.1 --- Band Model --- p.123 / Chapter E.2 --- Deconvolution Of Absorption Spectrum --- p.124 / Chapter F. --- Discussions --- p.131 / Chapter G. --- Conclusions --- p.133 / Appendix A --- p.134 / Chapter A.1 --- An Outline On The Theoretical And Experimental Aspects Of PDS --- p.134 / Chapter Chapter 7 --- Recrystallization Of Amorphous Germanium By Rapid Thermal Annealing --- p.165 / Chapter A. --- Introduction --- p.165 / Chapter B. --- Theory --- p.166 / Chapter B.1 --- Recrystallization Of Amorphous Germanium --- p.166 / Chapter B.2 --- Nucleation And Growth - Isothermal Transformation --- p.167 / Chapter B.3 --- The Structure Of Polycrystalline Aggregates By X-ray Analysis --- p.170 / Chapter C. --- Experimental Set-ups --- p.172 / Chapter C. 1 --- The Rapid Thermal Processing Unit --- p.172 / Chapter C. 2 --- The Conventional Furnace --- p.175 / Chapter C. 3 --- The X-ray Diffractometer --- p.175 / Chapter C. 4 --- Electrical Conductivity Measurements --- p.176 / Chapter D. --- Experimental Method --- p.177 / Chapter D.1 --- The Samples --- p.177 / Chapter D.2 --- The Experiments --- p.177 / Chapter E. --- Results And Discussions --- p.178 / Chapter F. --- Conclusions --- p.185 / Appendix A --- p.216 / Chapter Chapter 8 --- Conclusions --- p.217 / Chapter A. --- Conclusions --- p.217 / Chapter B. --- Suggestions On Improvement And Further Development Of The Present Systems --- p.219 / References --- p.221

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Constant strain rate compression and torsion tests were carried out isothermally at temperatures of 875 to 1075(DEGREES)C on a series of six steels. The base steel had a composition of 0.06% C and 1.43% Mn and the others contained one of the following sets of additions: (i) 0.035% Nb; (ii) 0.035% Nb + 0.115% V; (iii) 0.035% Nb + 0.30% Mo; (iv) 0.035% Nb + 1.90% Mn; (v) 0.115% V. The tests were conducted to determine the effects of Mn, Mo, Nb and V, singly and in combination, on the high temperature flow and recrystallization behavior of the materials. The dynamic precipitation kinetics for Nb(CN) and VN were determined by the Weiss method. The two PTT curves were similar, with the nose of the VN curve being situated at a slightly lower temperature (885 vs. 900(DEGREES)C) and at a somewhat longer time (26 vs. 16 s), in agreement with the lower equilibrium solution temperature of VN. The dynamic precipitation kinetics of Nb(CN) were retarded by the addition of Mn, V or Mo. This retardation is attributed to the increased carbonitride solubility that follows the addition of these elements because of the way in which they decrease the C and N activity coefficients. / RTT curves were constructed for dynamic recrystallization in the six steels investigated. These were derived from the peak strains of the compression flow curves, as determined at a strain rate of 3.7 x 10('-2)s('-1). Recrystallization occurred earliest in the plain C steel followed fairly quickly by the 0.115% V steel. All of the Nb bearing steels recrystallized considerably later, with the greatest retardation being noted in the 0.3% Mo steel, where it was nearly twice that due to Nb addition alone. This very large effect, and the retardation due to each of the transition elements, is explained in terms of the electronic differences between iron and the particular element. The effect of the atomic size differences with respect to iron is also considered. / The strengthening due to the presence of Mn, Mo, Nb and V in solution was determined from the yield strengths of these steels. The increment in yield strength over that of the plain C steel was determined as 70% and 7% per 0.1 at.% of Nb and V when each is added singly. The strengthening increased to 80% and 8% respectively for these elements when present jointly in austenite. The strength increments were 9% for Mo and 1.3% for Mn per 0.1 at.% when added to a 0.035% Nb steel. The rank order of these effects is also explained in terms of the electronic and atomic size differences, and a possible reason for the synergistic effect (e.g. in the case of Nb and V in a Nb-V steel) is proposed.