In the work which follows, the changes in structure of natural and electrolytic films brought about by various treatments will be the subject under discussion, and the experimental account will be concerned with the report of some effects encountered in the investigation of these oxide films. The confused and sometimes contradictory nature of the existing evidence regarding the nature and behavior of oxide films on aluminum is considered as sufficient justification for further study of the subject. It is hoped that some of the contradictory results obtained by other investigators may be explained on the basis of their experimental conditions and the interpretation of the data obtained.

The properties of pressure-induced flow of liquid helium II have been studied by the observation of the temperature and pressure dependence of the flow in narrow channels. The channels are in the form of an annular slit between two flat glass plates. Measurements of the flow rates have been made with hydrostatic pressures up to 2.3 x 103 dynes/cm 2, at temperatures between 1.39 and 2.10°K, and with slit widths of 2.4 and 4.3 microns. The observed flow rates have the same temperature dependence as the superfluid concentration in helium II. At lower pressure heads the flow rate is proportional to a power of the pressure head. The power is nearly independent of temperature but decreases with decreasing slit width. At higher pressures the flow rates reach saturation values at which they are independent of pressure. These saturation rates also have the temperature dependence of the superfluid concentration. The modifications necessary in the existing theories to explain these results are considered in a qualitative manner, and the need for further experiments of this nature is pointed out.

Abstract Not Available.

Abstract Not Available.

Abstract Not Available.

Abstract Not Available.

The cooling of a surface when thermionic electrons are emitted has been measured by Richardson and others. The results obtained for tungsten and other metals are consistent with recent determinations of the work functions by thermionic and photoelectric methods. The purpose of the research, here described, was to determine the cooling of a surface when photoelectrons are emitted. In the determination of the cooling of a surface when photoelectrons are emitted, the small electron currents possible demand a very sensitive temperature measurement. A bolometer method similar to that used in the thermionic work was first tried but did not prove satisfactory; so this method was discarded, and thermocouples were used instead. Two similar photoelectric cells were illuminated with the same source of light. Each cell contained a small platinum plate coated with caesium, the temperature of which was measured with an Fe-Ni thermocouple. The thermocouple junctions of the two cells were connected in series with a galvanometer in such a manner that the e.m.f's of the two cells opposed each other. In this way it was possible to determine, with the galvanometer, the change in temperature when the photoelectric current was allowed to flow or was stopped in one of the cells. The photoelectric current was controlled by the potential of the anode.

The Single Electron Transistor (SET), especially its variation the radio frequency single electron transistor (RF-SET), is a fast and ultra-sensitive electrometer working in the vicinity of the quantum limit. In this thesis, the theory and techniques related to the SET in the normal state and the superconducting state are introduced The thesis focuses especially on our efforts of improving the sensitivity of superconducting RF-SET, including: the design and fabrication of an all superconducting near loss-less matching network for improving the RF modulation, our early investigation of the sensitivity and linearity of a superconducting SET (S-SET) subject to quantum fluctuations of quasiparticles and Cooper pairs under different tunneling mechanisms, and our recent work approaching the quantum sensitivity limit using a double Josephson quasiparticle (DJQP) cycle of a S-SET. Using an effective bath description, we have found that the S-SET provides damping of the resonator modes proportional to its differential conductance, and has an effective temperature that can be well below both the ambient temperature and the energy scale of the bias voltage. In the region of negative differential conductance (NDC), the S-SET shows negative damping and a negative temperature. In the final part of the thesis, I have demonstrated our first application of an RF-SET for real-time detection of electron tunneling through a quantum dot.

As the size of a physical system decreases toward the nanoscale, quantum mechanical effects such as the discretization of energy levels and the interactions of the electronic spins become readily observable. To understand what happens within submicrometer scale samples is one of the goals of modern condensed matter physics. Electron transport phenomena drew a lot of attention over the past two decades or so, not only because quantum corrections to the classical transport theory, but also they allow us to probe deeply into the microscopic nature of the system put to test. Although a significant amount of research was done in the past and thus extended our understanding in this field, most of these works were concentrated on simpler examples. Electron transport in strongly correlated systems is still a field that needs to be explored more thoroughly. In fact, experimental works that have been done so far to characterize coherence physics in correlated systems such as ferromagnetic metals are far from conclusive. One reason ferromagnetic samples draw such attention is that there exist correlations that lead to excitations (e.g. spin waves, domain wall motions) not present in normal metals, and these new environmental degrees of freedom can have profound effects on decoherence processes. In this thesis, three different types of magnetic samples were examined: a band ferromagnetism based metallic ferromagnet, permalloy, a III-V diluted ferromagnetic semiconductor with ferromagnetism from a hole-mediated exchange interaction, and magnetite nanocrystals and films. The first observation of time-dependent universal conductance fluctuations (TD-UCF) in permalloy is presented and our observations lead to three major conclusions. First, the cooperon contribution to the conductance is suppressed in this material. This is consistent with some theoretical expectations, and implies that weak localization will be suppressed as well. Second, we see evidence that domain wall motion leads to enhanced conductance fluctuations, demonstrating experimentally that domain walls can act as coherent scatterers of electrons. Third, the temperature dependence of the fluctuations is surprisingly strong, suggesting that the dominant decoherence mechanism in these wires is different than that in similar normal metal nanostructures. The first observation of TD-UCF in diluted magnetic semiconductors (DMS) is also presented. In contrast to analogous measurements on permalloy samples, we find a surprising suppression of TD-UCF noise in this material at low temperatures, independent of field orientation. We believe this implies that the suppression is not due to an orbital effect, and therefore some of the fluctuations originate with time-varying magnetic disorder. The temperature dependence of the TD-UCF implies either an unusual fluctuator spectrum or a nonstandard dephasing mechanism. Measurements of UCF as a function of magnetic field allow an order of magnitude estimate of the coherence length at 2 K of approximately 50 nm in this material. The last samples examined were magnetite nanocrystals and films. Magnetite has been used in technologies for millennia, from compasses to magnetoelectronic devices, although its electronic structure has remained controversial for seven decades, with a low temperature insulator and a high temperature "bad metal" separated by the Verwey transition at 120 K. A new electrically driven insulator-metal transition below the Verwey temperature in both magnetite films and nanocrystals was observed. The possibility that this was a thermal effect was tested through various methods, and we have shown that the transition is in fact truly electrically driven. This electrically driven transition also showed a great deal of rigidity against external magnetic field and high gate voltages.

Single-Walled Carbon Nanotubes (SWNT) have been found to have excellent solubility in super acids such as 100+% H2SO4, and chlorsulfonic acid. The solutions display liquid crystalline behavior at high concentrations in super acids. Traditional wet-spinning method has been applied to SWNTs to make fibers from SWNTs only with the assistance of 100+% H2SO 4 (neat SWNT fibers). Extensive conditions, including concentrations, coagulation, and operation temperature, have been explored with Daca mixer and other custom-designed apparatuses (SBM and Refined Mixer). Fibers' properties have been tremendously improved through the research. Different characterizations have been done and all of them confirmed the neat SWNT fibers have the best alignment to-date among any macroscopic neat SWNT articles, as well as electrical conductivities. Meanwhile, neat SWNT fibers were used for X-ray diffraction study. For the first time, direct evidence has been provided to support the strong intercalation between SWNTs and super acids. Interestingly, for the first time, it has been reported that liquid sulfuric acid forms shell structure while exposed to SWNTs.