Thesis (Ph.D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 24, 2009) Vita. Includes bibliographical references.

Thesis (M.S.)--University of Toledo, 2008. / Typescript. "Submitted as partial fulfillment of the requirements for Master of Science in Physics." "A thesis entitled"--at head of title. Bibliography: leaves 129-133.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / Committee Chair: A. Rahmen M. Zaghloul ; Committee Members: W. Russell Callen and P. Douglas Yoder. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Spectroscopic ellipsometry is a nondestructive, ambient surface analysis technique for studying surfaces, interfaces and thin films. To take advantage of this method an automatic spectroscopic ellipsometer was designed and constructed for the microstructural characterization of thin films. This high precision instrument is capable of measuring in real-time the optical properties of bulk or thin film materials over the visible-UV region (1.5 - 6.0 eV). The microstructure of thin films can be determined from an effective medium theory analysis of the spectroellipsometric data to investigate how the film morphology evolves with varying preparation conditions and to determine the optimum deposition parameters. In this thesis the pseudodielectric function of palladium films prepared by dc planar magnetron sputtering was measured while the substrate temperature, argon partial pressure and rf-induced substrate bias were varied independently during deposition. The film data are in excellent agreement with the effective medium theory of Sen, Scala, and Cohen, relevant for a random coated-particle microstructure where the grains are optically isolated from each other. With increasing substrate temperature, the Pd volume fraction in the bulk was found to decrease slightly, while the rms microroughness of the film surface increased in magnitude. At 190° C, the rms microroughness was 80 ± 3 Awith the Pd volume fraction in the bulk region falling slightly to 97 ± 1% relative to the film deposited at 22° C. For argon partial pressures below a transition pressure, Pt≃15 mTorr, the films consisted of densely packed grains, corresponding to the zone T in Thornton's structure zone model. Above this transition pressure, the films developed into a more voided columnar structure, characteristic of the zone 1 region. A microstructural analysis indicated a general trend towards increased porosity and microroughness of the films with higher argon pressures. The zone 1 region was best described optically by a random coated-particle microstructure and the electron microscopy confirmed that for thin films prepared at argon pressures higher than Pt, the grains became isolated by void boundaries. The optical data could not distinguish whether or not the films were 2- or 3-dimensionally isotropic. With increasing rf-induced substrate biasing, the Pd film microstructure was modified in a manner similar to that obtained by varying the substrate temperature alone. Significant resputtering of the Pd films occurred, varying from 2 to 11 A/sec for bias voltages of -550 V to -1375 V, respectively. The measured deposition rate while bias sputtering was significantly higher than that expected upon the measured resputtering rate and several mechanisms were proposed to account for the enhancement in the deposition rate. The films were best characterized by a 2-dimensional isotropy which was supported by the columnar nature of the films observed by electron microscopy. Finally, the dielectric function of the "best" palladium film is compared to optical constants of Pd previously reported in the literature for bulk and thin film specimens. While all the authors quote essentially the same values for the real part of the dielectric function, regardless of the preparation or measurement technique, the imaginary part differs up to a factor of two. Surface microroughness, bulk porosity and oxide layers are unable to account for the difference. A possible grain boundary scattering mechanism is suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Title: Optical and magneto-optical spectroscopy of materials with antiferro- magnetic interaction Author: Bc. Katarína Križanová Department: Institute of Physics of Charles University Supervisor: RNDr. Jakub Zázvorka, Ph.D., Institute of Physics of Charles University Abstract: One of the goals of spintronic research is the efficient external con- trol of magnetic moment. Non-collinear antiferromagnets in the antiperovskite structure, such as Mn3NiN, show a piezomagnetic effect that can be used to utilize these materials in applications. In the strain free state, the material ex- hibit zero net magnetic moment. Using strain induced by a lattice constant mismatch between the thin layer and a substrate on which the thin film is applied on a non-zero net magnetic moment can be registered. Magneto-optical Kerr effect spectroscopy is used to investigate the non-collinear magnetic thin films. The effect of two substrate layers with resulting opposite sign of strain influencing the magnetic ordering of the antiperovskite material is studied with respect to sample temperature. Results show comparable spectral dependence with opposite sign of the Kerr effect caused by the opposite direc- tion of net magnetization moments. Ellipsometry measurements depending on sample orientation are performed to study the material...

Process dependent microstructural effects in ferroelectric SrBi2Ta2O9 (SBT) thin films were characterized and distinguished from material dependent optical properties using a systematic multi-layer modeling technique. Variable angle spectroscopic ellipsometry (VASE) models were developed by sequentially testing Bruggeman effective-media approximation (EMA) layers designed to simulate microstructural effects such as surface roughness, porosity, secondary phases, and substrate interaction. Cross-sectional analysis by atomic force microscopy (AFM), transmission and scanning electron microscopy (TEM) and (SEM) guided and confirmed the structure of multi-layer models for films produced by pulsed laser deposition (PLD), metal-organic chemical vapor decomposition (MOCVD), and metal-organic deposition (MOD). VASE was used to estimated the volume percentage of second phase Bi2O3 in SBT thin films made by MOD. Since Bi₂O₃ was 10 orders of magnitude more conductive than SBT, second phase Bi₂O₃ produced elevated leakage currents. Equivalent circuits and percolation theory were applied to predict leakage current based on Bi₂O₃ content and connectivity. The complex role of excess Bi2O3 in the crystallization of SBT was reviewed from a processing perspective. VASE helped clarify the nature of the interaction between SBT films and Si substrates. When SBT was deposited by MOD and annealed on Si substrates, the measured capacitance was reduced from that of SBT on Pt due mainly to the formation of amorphous SiO₂ near the SBT/Si interface. VASE showed that the thickness and roughness of the SiO₂ reaction layer increased with annealing temperature, in agreement with TEM measurements. Unlike PZT, SBT crystallization was not controlled by substrate interaction. / Master of Science

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Transmission ellipsometry is governed by the transmission ellipsometric function (TEF) of a film-substrate system. The function can be analyzed through a series of constant-thickness contours and constant-angle-of-incidence contours in the complex plane. It has been observed that these TEF contours for a zero film-substrate system bear strong resemblances to the families of curves that make up the Smith chart for transmission lines. In this thesis we present a comparative study of the TEF and the Smith chart, specifically through the distinct similarities of their respective families of curves. It is shown that both TEF and Smith chart have similar contours in both the positive and negative imaginary half planes. The Smith chart’s contours originate from a complex plane with linear boundaries. It is bisected into symmetric positive and negative imaginary half planes of equal areas that are conjugate of each other. When transformed to the Smith chart, it is normalized and the conjugate relationship remains intact. All contours in the positive imaginary half plane of the Smith chart are symmetric to all of the contours in the negative half plane of the Smith chart. TEF contours originate from a non-complex reduced thickness plane. This plane has a non-linear upper boundary. It is bisected into two equal areas but non-symmetric, half planes. When transformed to the complex τ plane, the likeness of the constant-angle-of-incidence contours and constant-thickness contours to the Smith chart contours become a function of the material indices. As the film-substrate systems material indices are increased, the range of the non-linear boundary of the ф – dr plane is reduced and the TEF contours more closely resemble the Smith chart.