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Dynamics And Thermodynamics Of The Quasi-Two Dimensional Magnetic Systems, Igor V. Rojdestvenski
Dynamics And Thermodynamics Of The Quasi-Two Dimensional Magnetic Systems, Igor V. Rojdestvenski
Digitized Theses
In recent years a considerable research effort has been put into the understanding of the physical properties of quasi-two-dimensional magnetic systems. Theoretical investigations help to explain many current experimental results. The aim of this thesis is to study dynamic and critical properties of certain quasi-two-dimensional magnetic systems.;In the first part of the thesis (Chapters 2 and 3) the Handscomb Monte-Carlo method is applied to investigate the critical behavior of the S = {dollar}1\over 2{dollar} Heisenberg ferromagnetic film with the number of monolayers L {dollar}\le{dollar} 3. We confirm the renormalization group results for the two-dimensional model for a wide range of …
Compositional Analysis Of Gate Dielectric Films, Hongtao Tang
Compositional Analysis Of Gate Dielectric Films, Hongtao Tang
Digitized Theses
Oxynitride has recently drawn attention as a candidate gate dielectric material for deep sub-micron devices, e.g. MOSFET's. Since the oxide growth rates in pure oxygen are high, efforts to scale down device dimensions with high quality ultrathin ({dollar}<{dollar}100A) SiO{dollar}\sb2{dollar} films are encountering some difficulties. Recently, it has been found that oxynitride films fabricated directly by a N{dollar}\sb2{dollar}O-rapid thermal processing method exhibit improved electrical properties compared to SiO{dollar}\sb2{dollar} films. Structural analysis for such oxynitride films is necessary in order to understand the physical reasons behind the observed improvements.;Nuclear reaction analysis combined with a chemical step-etching method was performed to depth profile nitrogen quantitatively in N{dollar}\sb2{dollar}O-RTP grown oxynitride films. The oxynitride dielectric composition dependence on growth conditions in a rapid thermal processing system was also investigated by nuclear reaction analysis. It is found that most N in the oxynitride films accumulates in a region close to the interface (less than 25 A from the interface in the oxynitride). Both N concentration and film thickness increase with temperature. Furthermore, a UHV initial growth study of oxynitride films on a Si(100) substrate was carried out by nuclear reaction analysis and Auger electron spectroscopy. The results clearly confirm that the nitrogen involvement occurs primarily before an oxynitride film thickness of {dollar}\sim{dollar}25 A is developed, and the subsequent film growth is dominated by oxidation. For the first time, it is found that there is a special growth period at the very beginning during which nitridation (with no simultaneous oxidation) dominates the growth process. It is speculated that the phenomenon results from a competition between reactions of Si with O and N. The dependence of film growth on temperature is such that below 950{dollar}\sp\circ{dollar}C, there is little nitrogen incorporated in the oxide film.
Theory Of Spin Waves In Heisenberg Ferromagnetic And Antiferromagnetic Thin Films With Nonuniaxial Single-Ion Anisotropy, Paula R. Heron
Theory Of Spin Waves In Heisenberg Ferromagnetic And Antiferromagnetic Thin Films With Nonuniaxial Single-Ion Anisotropy, Paula R. Heron
Digitized Theses
This thesis describes the microscopic, quantum mechanical theory of exchange-dominated spin waves in Heisenberg ferromagnetic and antiferromagnetic thin films including the effects of nonuniaxial single-ion anisotropy. The results constitute a generalization of previous theoretical studies on spin waves in thin films with uniaxial anisotropy and in semi-infinite ferromagnets with nonuniaxial anisotropy.;A spin Hamiltonian containing nearest-neighbour exchange terms, Zeeman terms, and single-ion anisotropy terms is used. The films may be asymmetric with respect to surface exchange and anisotropy parameters which are also assured to be perturbed from the bulk values. The results apply both to cases in which the nonuniaxial anisotropy …
Using The Quantum Mechanical Path Integral In Quantum Field Theory, Siu Kwan Wong
Using The Quantum Mechanical Path Integral In Quantum Field Theory, Siu Kwan Wong
Digitized Theses
Matrix elements of the form {dollar}\langle x\vert\exp({lcub}-{rcub}iHt)\vert y\rangle{dollar} arise when operator regularization, a symmetry-preserving regulating procedure that avoids explicit occurrence of divergences, is employed to do perturbative calculations in quantum field theory. In recent years, it is shown that this matrix element can be evaluated using a path integral encountered in single particle quantum mechanics. This technique has the advantage of eliminating loop momentum integrals and algebraically complicated vertices in gauge theories. We develop this technique to handle various problems. Our approach is similar to but distinct from the one of Polyakov and Strassler which is related to the string …