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- 1. J. Phys. Chem. 88, 5255-5260 (1984) , “Dynamic Interchange among Three States of Phosphorus (4+) in ?-Quartz. 2.”, Y. Uchida, J. Isoya, J. A. WeilThe dynamic process due to electron jumping among three states with different sp hybrid directions in the quasitetrahedral P4+ center [PO4]0 in a-quartz has been investigated by 10-GHz electron paramagnetic resonance, over the temperature range 40 to 400 K. The relative populations (mole fractions ƒІ and ƒІІ) of the ground state P(І) and two degenerate thermally excited states P(ІІ) were determined from the measured EPR absorption line intensity ratios and from the line positions of the averaged state P(A), respectively, in the slow and fast kinetic regions. The temperature dependence of the mole fractions has been explained by considering vibrational sublevels in the potential well describing each state. The jump rate was also obtained, via EPR absorption line-width analysis based on the Bloch equations, in both the slow and the fast regions. The characteristic parameters of the dynamic process, Le., energy separation and vibrational sublevels of the ground and excited states, and barrier height between these, have been determined. (Read more)
- 2. J. Phys. Chem. 83, 3462-3467 (1979) , “Dynamic Interchange among Three States of Phousphorus 4+ in ?-Quartz”, Y. Uchida, J. Isoya, J. A. WeilDynamic averaging due to electron jumping among three states with different sp hybrid directions in the P4+ center [PO4]0 in α-quartz has been studied by single-crystal electron paramagnetic resonance. The spin-Hamiltonian matrices g and Aslp for low temperature (i.e., C140 K) spectra P(І) and P(Ⅱ) and for high temperature spectrum P(A) are reported. For each crystal site, the line positions of P(A) agree well with those derived from the matrices measured for the three states. i.e., with weighted averages including P(І) and the two symmetry-related P(Ⅱ) spectra. (Read more)
- 3. Lattice Defects in Semiconductors 23, 1-22 (1975) , Institute of Physics, London , “EPR Studies of the Lattice Vacancy and Low-Temperature Damage Processes in Silocon”, G. D. Watkins.EPR studies of silicon irradiated at 20.4 K and 4.2 K by 1.5 MeV and 46 MeV electrons are described. In 46 MeV irradiations the dominant defects formed appear to be divavancies and other multiple defect aggregates which liberate vacancies throughout the anneal to room temperature as they reorder, recombine, etc. For 1.5 MeV irradiations group III atoms play a vital role in p- and n-type materials in trapping interstitials and stabilizing damage. Carbon and oxygen are not effective interstitial traps at these temperatures. Evidence of limited vacancy migration during irradiation is also cited. Two distinct excited configurations of vacancy-oxygen pairs are identified as precursors to A-centre formation in n-type silicon. The kinetics for their conversion to A-centres depends strongly upon the Fermi level as does the isolated vacancy migration energy whhich is measured to be 0.18 ± 0.02 eV for the V= charge state. The vacancy has four charge states, V+, V0, V- and V=. Kinetics for hole release from V+ reveals an activation barrier of 0.057 eV. The concentration of V+ at 20.4 K in boron-doped material indicates the corresponding donor level even closer to the band edge, approximately EV + 0.039 eV. Jahn-Teller energies for V0, V+, and V- are estimated from stress-alignment studies and confirmed to be large. Kinetics studies for reorientation from one Jahn-Teller distortion to another are also described for each charge state.
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