Noncontact atomic force microscopy (NC-AFM) was applied to investigating the creation of monatomic depth rectangular pits, the growth of metals, and the templated growth of molecules on the KBr (001) surface under ultrahigh vacuum conditions. The pits were produced by a new method where the sample is exposed to a controlled dose of charge from an electron beam evaporator. The structure and size distribution of the pits was characterized by NC-AFM. For the metal growth studies, gold, tantalum, and palladium were deposited onto KBr by electron beam deposition. The gold produced tall multiply twinned and epitaxial nanoparticles, while the tantalum formed flatter fractal islands. The palladium growth resulted in the creation of rectangular KBr islands in addition to palladium nanoparticles. Despite the use of a charge deviating grid, charge played an important role during the metal growth. In particular, the number density of gold nanoparticles followed nearly the same temperature dependence as the pits, suggesting that the metal nanoparticles nucleate predominantly at defect sites created by incident charge. The effect of charge was also seen in the tantalum system where pits surrounded the nanoparticles prepared at elevated temperatures. By creating pits before depositing gold, it was shown that the pits edges can be used to template the growth of metals. It was also shown that the pits can be used to trap PTCDA molecules and to align C60 molecules with the <100> direction of the substrate. Molecular resolution NC-AFM measurements were used to determine the structures and lattice constants of the molecular nanostructures. Experiments involving the sequential growth of metals and molecules showed that the order of deposition and the strength of the molecule-metal interaction are key factors in determining the nature of the growth. Furthermore, it was shown that metal structures can be used to nucleate the growth of sufficiently strongly interacting molecules.

The AC phase-coherent transport in mesoscopic structures is studied via a scattering approach. A general theory is presented under the guidance of two physical principles: charge and current conservation, gauge invariance. As the AC response is intrinsically a many-body problem, we have to treat the scattering problem and the charge redistribution effects in a self-consistent manner. / One quantity of particular interest is the mesoscopic capacitance. In mesoscopic structures where the electric screening length is comparable to the geometric size, the experimentally relevant capacitance is no longer due to geometry alone but to the electro-chemical potential and the capacitance crucially depends on the density of states of the conductor. Furthermore, the phase-coherent nature of the carrier motion leads to striking asymmetric effects in the magneto-capacitance. The general theory is put forth into numerical simulations where the theory is justified. / The study of AC transport in mesoscopic structures should not only help us to better understand the physics of many-body systems, but should also provide valuable knowledge in characterizing and controlling small electronic devices which is of great technological importance.

The effect of composition on the mechanical properties of high Al content Al-Y-Ni metallic glasses has been studied. Nine samples in all were prepared with a composition of ${ rm Al sb{85}Y} sb{x}{ rm Ni} sb{15-x}({ rm x}=3, ...,11).$ The amorphous alloys were first tested using both XRD and DSC. The DSC runs revealed that the samples were made up of two different types: one showing no glass transition and a lower crystallization temperature, and the other showing a distinct glass transition with a higher crystallization temperature indicating that they are truly homogeneous glasses. The samples showed a Young's modulus that does not seem to reveal any distinct compositional dependence whereas, the tensile strengths showed a distinct decreasing trend with increasing Y content. Values of various mechanical properties and crystallization temperatures obtained in this study are compared to those reported by other groups. We find very high specific strengths in these glasses, which combined with their excellent ductility makes them ideal structural materials. The effect of annealing is also examined and it is found that the samples lose a large proportion of their tensile strength and ductility when annealed.

Previous studies on Al85Yx Ni15-x glasses established a correlation between crystallization mode (pure growth versus nucleation and growth) and crystallization product. Glasses with approximate compositions x = 5, 7, 8, 10 were studied in order to accurately ascertain the nature of the structural variance which gives rise to different crystallization modes and the identity of the resulting crystallization products. Glasses with x = 5, 10 have a clear distinction: x = 5 contains quenched-in Al nanocrystals which act as nucleating centers leading to alpha-Al as the first crystalline product; equilibrium crystalline phases are alpha-Al, Al3Ni and a stacking variation of Al4YNi. x = 10 is a homogeneous glass which undergoes a glass transition prior to crystallization; first crystalline product is an unstable FCC structure which breaks down via Al segregation; equilibrium phases are alpha-Al, beta-Al3Y and Al16YNi 3. x = 7,8 share these characteristics: x = 7 contains quenched-in Al-nanocrystals and follows the initial x = 5 pattern of primary Al crystallization; however it undergoes a glass transition prior to first stage crystallization and equilibrium phases are alpha-Al, beta-Al3Y and Al16YNi3. x = 8 crystallizes by nucleation and growth yet has identical crystallization products as the corresponding x = 7 crystallization stages. Isothermal annealing prior to first two crystallization stages of x = 8 yields alpha-Al and the unstable FCC structure. Isothermal crystallization is complex, frequently involving the overlap of multiply nucleating phases and the sequential nucleation of successive crystallization stages at the same annealing temperature. The results of these crystallization studies imply that Al-Y-Ni glasses obey the cluster model (Al-Y versus Al-Ni clusters) where cluster-cluster correlation establishes the degree of medium-range order and presence or absence of Al nanocrystals. (Abstract shortened by UMI.)

A phenomenological theory of magneto-optic Kerr effect (MOKE) is presented to illustrate the connection between the magnetization and the polarization of light reflection in an isotropic medium. An apparatus measuring the MOKE of magnetic medium was designed and constructed. The surface magneto-optic Kerr effect (SMOKE) of a magnetic multilayer is a measurement of the average magnetization of several layers within the penetration depth of the light. / SMOKE measurements on a series of sputtered $ rm Ni sb{80}Co sb{20}15 A$/CU$(t sb{Cu}),$ where $t sb{Cu}$ is the thickness of Cu spacer layer, multilayers confirms that the coupling strength in these multilayers oscillates from antiferromagnetic (AF) coupling to ferromagnetic coupling as a function of Cu spacer layer thickness. Low-angle x-ray diffraction and SMOKE measurements on a series of AF-coupled $ rm (Ni sb{80}Co sb{20}15 A$/Cu20A) $ times$ N multilayers with bilayer numbers N ranging from 8 to 100 shows that cumulative interface roughness increases with increasing N, as do the saturation field and coercivity. This is possibly due to the out-of-plane anisotropy associated with cumulative interface roughness in multilayers. / An AF-coupled $ rm (Ni sb{70}Co sb{30}15 A$/Cu20A) $ times$ 10 was continually annealed up to 400$ sp circ$C in several steps, and the magnetic behaviour of the sample was evaluated as a function of annealing temperatures. $ rm (Ni sb{70}Co sb{30}15 A$/CU20A/Ni$ rm sb{70}Co sb{30} A$/CU20A) $ times$ 5 multilayer was used for investigating the AF coupling between magnetic layers of unequal thicknesses. Finally, an AF-coupled $ rm (Ni sb{70}Co sb{30}15 A$/Cu20A/Ni$ rm sb{70}Co sb{30}15 A$/Cu35A) $ times$ 5 multilayer was sputtered and used to study the magnetization of an AF-coupled multilayer with two different coupling strengthes.

The Ca$ sb{x}$K$ sb{1-x}$(NO$ sb3) sb{1+x}$ glass system has been studied by means of X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The structure of the glass system was studied in XRD experiments and from the Radial Distribution Function (RDF). A structural model for this glass system was suggested with the agreement between the RDF calculation and structure model geometric calculation. DSC studies ranged from glass transition and crystallization to melting. The activation energy for crystallization was obtained. / The difficulty of handling the glass in open air was overcome by using vacuum tube to melt the sample and glove box with Ar gas to handle the glass. It is found that the handling of the samples, i.e. avoiding exposure to moisture is critical to maintaining sample quality. / For the structural studies, glasses of $ rm Ca sb{0.4}Na sb{0.6}(NO sb3) sb{1.4}, Ca sb{0.4}Rb sb{0.6}(NO sb3) sb{1.4}$ and $ rm Mg sb{0.4}K sb{0.6}(NO sb3) sb{1.4}$ were also prepared for comparison with the $ rm Ca sb{x}K sb{1-x}(NO sb3) sb{1+x}$ glasses. The same structural model applied to all of them with similar agreement. / For the DSC studies, only the $ rm Ca sb{x}K sb{1-x}(NO sb3) sb{1+x}$ glasses were used. The relation between increase of glass transition temperature $T sb{g}$ and that of divalent cation concentration is linear. It was observed that unlike the metallic glass system, the crystallization activation energies do not change with the glass composition. We also observed the irreversible relaxation effect in this glass system and the effect of supercooling in the DSC to form the glass.

We study the behavior of a simple cubic crystal interface through the analysis and simulation of the Ising model in three dimensions; we use an algorithm which permits local temperature variations by emulating thermal diffusion. We derive a description of the interface based on the thermal fluctuation population at equilibrium and then use it to identify the equilibrium and dynamic roughening transitions observed under a variety of circumstances including a planar interface at equilibrium, a metastable bulk inclusion, an evaporating inclusion and a planar interface in the presence of a driving force. We also study strongly driven interfaces which exhibit an instability and pattern formation behaviour known as the Mullins-Sekerka instability. We use a special two-dimensional version of the simulation model to examine the linear growth of unstable modes of a driven interface; we compare our simulation data to theoretical predictions for the cases of an unstable flat interface and circular disk interface. Returning to the fully three-dimensional code, we present simulation data of late-time dendrites growth, including an analysis of the information available in the thermal fields. We also show that, at low temperatures, the tips of dendrites are facetted and demonstrate a response to the driving force which is consistent with the dynamic roughening transition.

Order-disorder transitions have been studied for many years. The great number of experiments done on binary alloys makes condensed matter physics very appealing since it allows theory and experiment to progress side by side. / Using field theoretic methods, we study many aspects of physical systems such as binary alloys, which are taken out of thermodynamic equilibrium. In the introduction, an expose of basic notions is given. In the second chapter, we review an analytical method describing phase separation processes resulting from a critical quench. Physically, the latter phenomena could represent an initially disordered binary alloy, in which, following a drop in temperature, the atoms spontaneously order into a crystalline lattice. We will then study the effect a conserved field has on the kinetics of phase separation. This conserved field represents the local concentration of atoms of the alloy. In Chapter 4, we describe a theory formulated to explain some non-trivial relaxation of the structure factor seen experimentally for an initially ordered system suddenly cooled. Finally, we propose a theoretical model describing polymorphous crystallization. The model is studied via computer simulations. The results so obtained are compared to the experiment.

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