A newly designed Langmuir probe has been evaluated and was used to map the plasma potential near the powered electrode of a plasma etch chamber in 2 dimensions. Various electrode materials and geometries were used in order to investigate the relationship between electrode design and the presence of localized regions of elevated plasma potential. These regions of elevated plasma potential were known to be responsible for the presence of particle clouds suspended in the plasma during operation. A relationship was established between sharp edges on the powered electrode, insulating materials on the electrode and localized elevation in plasma potential. A thin layer of raised plasma potential has also been discovered at the plasma-sheath boundary. Suggestions for electrode design to reduce the presence of particles suspended in the plasma are made.

With the increasing demand for high storage density, magnetic recording media will soon have as their basic components single-domain ferromagnetic grains. Recently experimentalists working with powerful new microscopic techniques have discovered that the process of magnetization reversal in these grains is much more complicated than had been previously realized. In this dissertation we investigate the applicability of the two-dimensional kinetic Ising model on a square lattice as a model for the switching dynamics. The process of metastable decay is studied by two means: Monte Carlo simulations and analytical arguments based on droplet theory. The simulations are shown to be consistent with the analytical arguments and qualitatively similar to the experimental measurements of single-domain ferromagnets. / For a periodic Ising system with an initial magnetization $m\sb0$ = +1 in a negative magnetic field, the field $H\sb{\rm sw}$ which causes the magnetization to decay to zero in a specified length of time is found as a function of the system size L. The probability that the magnetization remains greater than zero is also found as a function of time for fixed applied field and as a function of applied field for fixed decay time. / The magnetostatic dipole-dipole interaction in real magnetic materials is modeled to lowest order by adding to the Ising Hamiltonian a term proportional to the square of the magnetization. The analytical predictions show excellent agreement with Monte Carlo simulations with no fitted parameters that depend on the $m\sp2$ term. / Finally, $H\sb{\rm sw}$ is found from Monte Carlo simulations of octagonal systems with a variety of boundary conditions. The results are explained in terms of the scaling form of the free-energy barrier which must be overcome for the metastable state to decay, and they demonstrate the importance that surface effects such as adsorption and reconstruction might have on magnetization switching. / Source: Dissertation Abstracts International, Volume: 57-04, Section: B, page: 2634. / Major Professor: Per Arne Rikvold. / Thesis (Ph.D.)--The Florida State University, 1996.

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When the thickness of a magnetic layer is comparable to (or smaller than) the electron mean free path, the interface between magnetic and non-magnetic layers becomes very important factor to determine magnetic properties of the ultra-thin films. The quality of interface can enhance (or reduce) the desired properties. Several interesting physical phenomena were studied using these interface effects. The magnetic anisotropy of ultra-thin Co films is studied as function of non-magnetic underlayer thickness and non-magnetic overlayer materials using ex situ Brillouin light scattering (BLS). I observed that perpendicular magnetic anisotropy (PMA) increases with underlayer thickness and saturates after 5 ML. This saturation can be understood as a relaxation of the in-plane lattice parameter of Au(111) on top of Cu(111) to its bulk value. For the overlayer study, Cu, Al, and Au are used. An Au overlayer gives the largest PMA due to the largest in-plane lattice mismatch between Co and Au. An unusual effect was found by adding an additional layer on top of the Au overlayer. An additional Al capping layer on top of the Au overlayer reduces the PMA significantly. The possible explanation is that the misfit strain at the interface between the Al and the Au can be propagated through the Au layer to affect the magnetic properties of Co even though the in-plane lattice mismatch is less than 1%. Another interesting problem in interface interdiffusion and thermal stability in magnetic tunnel junction (MTJ) structures is studied using X-ray photoelectron spectroscopy (XPS). Since XPS is a very chemically sensitive technique, it allows us to monitor interface interdiffusion of the MTJ structures as-deposited and during post-deposition processing. For the plasma-oxidized samples, Fe only participates in the oxidation reduction process. In contrast to plasma-oxidized samples, there were no noticeable chemical shifts as-deposited and during post-deposition processing in air-oxidized samples. However, peak intensity variations were observed due to interface interdiffusion.

This study was undertaken to gain a greater understanding of the growth mechanism of carbon nanoclusters. A set of carbon nanocluster samples prepared by three different methods and under different conditions was characterized with respect to morphology, structure, composition, and related properties. Electron microscopy characterization techniques were used to identify these features. The carbon nanoclusters prepared by conventional arc discharge, modified arc discharge, and catalytic CO disproportionation appear quite different on the surface, but have features in common that this study emphasizes. For the understanding of the growth mechanisms of carbon nanoclusters of different morphologies, the dependence of growth features on the major processing parameters--carbon supply and carbon activity, reaction temperature, gas type and partial pressure, composition and materials involved--was interpreted systematically in a comparative manner. For the encapsulation of foreign materials into carbon cages, the ratio of the supply of carbon and encapsulants, the dimensions and configurations of the electrodes, the flow of a buffer gas across the carbon source, the nature and surface area of materials to be encapsulated or acting as catalyst were recognized as the basic components of a process that lead to properties of as-made materials such as the size distribution of the clusters, the degree of the carbonization of the encapsulants, and the predominant presence of certain morphologies. Regarding the comparison of the structural stability of different morphologies, the results of the post deposition treatments such as elevated high temperature annealing, nitric acid erosion, and electron beam bombardment provide further insight into the properties of this novel family of materials. Operating in certain domains of the parameter space, carbon-coated ferromagnetic nanoparticles, single-walled nanotubes, cylindrical multi-walled nanotubes, and conical fish-bone filaments were produced and comparatively characterized. A tentative discussion with the aim of confirming, expanding or modifying some growth models that have emerged from the work of the past was given in this dissertation. It is expected that this broad-based comparative study will advance the understanding of the growth mechanism to a point where some of the technological promise of the carbon nanoclusters may be realized.

Lightning, a familiar phenomenon on Earth, may also occur at other times and locations in our solar system. It has been suggested as a mechanism for forming chondrules, millimeter-sized beads of glassy silicate found in primitive meteorites formed in the early solar system 4.5 billion years ago. It has also been detected in Voyager images of Jupiter, and there is evidence that it may occur on other planets as well, including Venus, Saturn and Neptune. The mechanism believed to produce lightning discharges on Earth, and possibly other planets, is charge production by collisions of ice particles, followed by gravitational separation of oppositely-charged large and small particles. This work examines the possibility of the occurrence of lightning discharges in the atmospheres of Jupiter and Neptune as well as in the protoplanetary nebula (PPN) of the early solar system by modeling charge separation and growth of the electric field. The model is also applied to the Earth as a test of its predictive power. It is found that the model can reproduce the correct timescale, particle charge and electric field magnitude seen in terrestrial lightning. The model also predicts lightning on Jupiter at the 3-5 bar level provided that the local water abundance is greater than the solar value. This is a much higher abundance than measured by the Galileo probe into Jupiter's atmosphere, which suggests that the water content measured by the probe does not apply to the entire planet. An application of the model to Neptune's water and NH₄SH clouds finds that lightning is unlikely in these clouds due to the large electric field required for electrical breakdown. Lightning may be possible in the overlying H₂S-NH₃ cloud provided that these substances can undergo collisional charge exchange with a magnitude at least 1% of that found in water ice. In the protoplanetary nebula, it appears that large-scale precipitation-induced lightning could not have occurred, due to the small mass density, low temperature and high electrical conductivity of the surroundings. This is a robust conclusion that does not depend sensitively on the values of the parameters involved.

With an always-increasing need for higher integration, the wireless industry poses challenges regarding miniaturization and high performance circuitry. In addition, the solutions require compatibility with the rest of the design for integration and manufacturing. The present work depicts the progress toward a novel, high quality, one-pole filter-resonator operating in the 5.6-5.8 GHz range. Quality factors up to 640 are demonstrated on Silicon planar structures with volume of 177 mm³. Further size reduction yielded a volume of 24.5 mm³ and a quality factor of 186.

Using the focused ion beam sputtering capabilities of Scanning Ion Microscope with Polarization Analysis (SIMPA), arrays of regular shaped particles with sizes in the order of 10$\mu$m are produced from a 35nm thick $\rm Ni\sb{83}Fe\sb{17}$ film with in-plane uniaxial anisotropy, The aspect ratio of the particles range from bar-like (50:1) to island-like (1.4:1). Their magnetic properties are studied with longitudinal magneto-optical Kerr effect. Structures with different geometries are found to display fundamental differences in their magnetic behavior. Two types of geometry induced changes in the magnetization reversal process are discerned. These changes are found to agree with a theoretical model based on micromagnetic effects. Light is scattered into a regular diffraction pattern from these structures. The magneto-optical effects in the various spectral orders are examined; they are found to produce similar hysteresis curves as the specular beam.

Mathematical models of rabbit atrial and ventricular myocytes that are based on quantitative voltage clamp data from emzymatically isolated cardiac myocytes have been developed. These models are capable of accurately simulating the transmembrane ionic currents recorded in response to a step change in membrane potential (whole-cell voltage clamp response), the nonpropagated membrane action potential (MAP), and the frequency-dependent action potential waveshape changes occurring in response to variations in rate of stimulation. Rectangular pulse, ramp and action potential voltage-clamp measurements of the transmembrane ionic currents have allowed us to model a number of processes thought to be important during repolarization. These computations provide important biophysical insights into the electrophysiological activity of atrial and ventricular cells and their associated intra- and extracellular ionic concentration changes. The present model also has useful predictive capabilities. We have used the model to: (1) estimate the intracellular $Ca\sp{2+}$ transient in these myocytes and to compare the relative occupancy of the $Ca\sp{2+}$ binding sites in the contractile proteins with known cellular mechanical activity, and (2) predict the response of the atrial cell to potassium current blockade via $BaCl\sb2$ to the bathing medium.

Epitaxial films of hcp Tb(0001) on bcc W(110) substrates are prepared and their geometric, electronic and magnetic properties are studied. The atomic flatness and cleanness and the single-crystalline state of the W(110) substrates and the Tb films are checked using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low-energy and high-energy electron diffraction (LEED and RHEED). Using electron capture spectroscopy (ECS), the surface electron spin polarization of the Tb(0001) films is studied as a function of temperature. The topmost layer is found to order ferromagnetically below a surface Curie temperature T$\sb{\rm C\sb s}$ = 249.96 K, which lies above both the bulk Curie and Neel temperatures T$\sb{\rm C\sb b}$ = 220 K and T$\sb{\rm N\sb b}$ = 228 K, respectively, and exhibits strongly non-monotonic behavior close to 245 K. Novel critical behavior is observed near T$\sb{\rm C\sb s}$, suggesting strong surface anisotropies, in accord with a recently predicted and previously unobserved surface phase transition.