by Yip Kam-wa. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography: leaf 64. / List of Figures --- p.iii / Acknowledgement --- p.vi / Abstract --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Effective-mass Approximation for Lattice-matched Heterostructures --- p.4 / Chapter 2.1 --- Introduction --- p.4 / Chapter 2.2 --- Formulation --- p.5 / Chapter 2.3 --- Model --- p.10 / Chapter 2.4 --- Exact Solution and Effective-mass Approximation for the Reflection Coefficient of 1-D Heterojunction --- p.15 / Chapter 2.5 --- Comparison --- p.20 / Chapter 2.6 --- Kinetic Energy Operator Ordering --- p.26 / Chapter 2.7 --- Conclusion --- p.30 / Chapter 3. --- Effective Hamiltonian for Semiconductor Heterostructures in a Uniform Magnetic Field --- p.33 / Chapter 3.1 --- Introduction --- p.33 / Chapter 3.2 --- Bloch Electron in a Uniform Magnetic Field --- p.34 / Chapter 3.3 --- Effective Hamiltonian for Heterostructures in a Uniform Magnetic Field --- p.40 / Chapter 3.4 --- Conclusion --- p.42 / Chapter 4. --- Effective-mass Approximation for a 1-D Strained Heterostructure --- p.43 / Chapter 4.1 --- Introduction --- p.43 / Chapter 4.2 --- Formulation --- p.44 / Chapter 4.3 --- Model --- p.50 / Chapter 4.4 --- Comparison --- p.54 / Chapter 4.5 --- Conclusion --- p.62 / Chapter 5. --- Conclusion --- p.63 / References --- p.64 / Appendix A --- p.65 / Appendix B --- p.67 / Appendix C --- p.68

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2004. / Thesis advisor(s): Gamani Karunasiri, Ronald E. Brown. Includes bibliographical references (p. 33). Also available online.

Approved for public release, distribution is unlimited / In this thesis, SiN films grown on Si substrates were characterized using Fourier Transform Infrared (FTIR) spectroscopy. The stress in SiN films can be used to enhance of mobility of electrons and holes which increases the performance of metal-oxide-semiconductor (MOS) transistors. The samples used in this study were prepared by Applied Materials using chemical vapor deposition (CVD) technique with different growth parameters. The stress of the samples varied from 1.3 GPa compressive to 1 GPa tensile depending on the growth conditions employed. The FTIR measurement showed three distinct absorption peaks associated with Si-N, Si-H and N-H vibrational modes. The hydrogen was unintentionally incorporated into the SiN film during the CVD process due to its use as the carrier gas for the precursors. It was found from the FTIR data that the area under Si-H and N-H peaks (amount of bonds) varies in opposite directions when the film stress changes from compressive to tensile. In addition, the peak position of the Si-H absorption shifted to higher energy while the opposite was true for N-H as the stress changes from compressive to tensile. The strength and the position of the Si-N absorption peak were found to be relatively insensitive to the stress of the film. This indicates that the amount of Si-H and N-H bonds in the film is responsible for controlling the stress of the film. The use of quantum calculation of SiN molecules with different amount of Si-H and N-H bonds was used toward understanding the experimental absorption spectra. / Lieutenant, Mexican Navy

Made available in DSpace on 2016-05-17T16:51:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-27. Added 1 bitstream(s) on 2016-05-17T16:54:31Z : No. of bitstreams: 1 000857078.pdf: 1812962 bytes, checksum: bde14a09d566d4e85bd92430eb397f6f (MD5) / Utilizamos as abordagens de potencial e massa efetiva e a de espaço de fase quântico para caracterizar propriedades da molécula magnética de Fe8. Na abordagem de potencial e massa efetiva obtemos a altura da barreira do estado fundamental, o hiato de energia devido ao tunelamento, a medida da temperatura de crossover, o campo magnético de pareamento de níveis e o de saturação. Na descrição de espaço de fase quântico, estudamos qualitativamente as correlações entre o par de variáveis envolvidas através das funções de Wigner e Husimi, calculamos o hiato de energia associado ao tunelamento e fornecemos uma medida via funcional de entropia para a correlação entre as variáveis momento angular e ângulo e sua respectiva intepretação / We have used an angle-based description and the quantum discrete phase space formalism to characterize Fe8 cluster properties. Through the angle-based approach we have calculated the the ground state barrier height, the energy splitting of the two lowest levels, the crossover temperature, the matching and the saturation magnetic field intensities. With the quantum phase space approach we also have used the energy splitting in order to study the spin tunneling of the lowest energy levels, a qualitative and a quantitative way to show the correlations between the angle and angular momentum variables via the Wigner and Husimi functions

Orientador: Diógenes Galetti / Banca: Armando Nazareno Faria Aleixo / Banca: Maria Carolina Nemes / Banca: Miguel Alexandre Novak / Banca: Rogério Rosenfeld / Resumo: Utilizamos as abordagens de potencial e massa efetiva e a de espaço de fase quântico para caracterizar propriedades da molécula magnética de Fe8. Na abordagem de potencial e massa efetiva obtemos a altura da barreira do estado fundamental, o hiato de energia devido ao tunelamento, a medida da temperatura de crossover, o campo magnético de pareamento de níveis e o de saturação. Na descrição de espaço de fase quântico, estudamos qualitativamente as correlações entre o par de variáveis envolvidas através das funções de Wigner e Husimi, calculamos o hiato de energia associado ao tunelamento e fornecemos uma medida via funcional de entropia para a correlação entre as variáveis momento angular e ângulo e sua respectiva intepretação / Abstract: We have used an angle-based description and the quantum discrete phase space formalism to characterize Fe8 cluster properties. Through the angle-based approach we have calculated the the ground state barrier height, the energy splitting of the two lowest levels, the crossover temperature, the matching and the saturation magnetic field intensities. With the quantum phase space approach we also have used the energy splitting in order to study the spin tunneling of the lowest energy levels, a qualitative and a quantitative way to show the correlations between the angle and angular momentum variables via the Wigner and Husimi functions / Doutor

This PhD work took place in the framework of theoretical research aimed at implementation of quantum computing schemes and algorithms in solid state devices. The electron and nuclear spins of dopant atoms implanted in silicon crystals, that already lie at the core of commercial diodes and the photovoltaic industry, are able to store quantum information longer than anything else in the solid state. Controlled manipulations of silicon qubits depend on the ability to tune the nanoscopic donor electron state: we provide a complete theoretical picture that includes, within the insightful and analytic framework of effective mass theory, the effects of the non-trivial silicon conduction band and the different lattice distortions caused by the implantation of the donor species. Calibration of the multi-valley bulk theory to account for binding energies and electron-nuclear hyperfine couplings allows improved estimates of the exchange splittings between two neighbouring donors, that provide the simplest handle for tuning two-qubit operations. Further refinements to our approach lead to exceptional agreement with experimental measurements of Stark effects, where an external electric field is used to enable local single qubit manipulations within global driving fields: we set reliable thresholds on such gating speeds across all group V donors. Finally, we propose a scalable scheme for silicon quantum computing that relies on the coherent transfer of information from Si:Bi donors, that are established as excellent memory qubits, to surface quantum dots that are easier to manipulate, within a topological surface code which enables outstanding tolerance to errors. Analysis of the optimal working regimes and inclusion of the leading sources of decoherence allow us to set out a robust design of the basic building block of future realizations.