Coupled plasmonic systems have been in the limelight recently for both their interesting fundamental physical properties, and their possible applications in sensing and optoelectrical system integration. Planar plasmonic systems, which can couple propagating and localized plasmons, show promise for integration of future on-chip optoelectronic devices. This thesis investigates such a system consisting of a planar metallodielectric grating coupled to spherical gold nanoparticles. It is shown that the addition of gold nanoparticles to a silver metallodielectric grating system can produce a profound change in the resonance response of the system. This coupling is shown to depend strongly on the size and surface coverage density of the gold nanoparticles.

Charge detection at microsecond time-scales has far reaching consequences in both technology and in our understanding of electron dynamics in nanoscale devices such as quantum dots. Radio-frequency superconducting single electron transistors (RF-SET) and quantum point contacts (QPC) are ultra sensitive charge sensors operating near the quantum limit. The operation of RF-SETs outside the superconducting gap has been a topic of study; the sub-gap operation, especially in the presence of large quantum fluctuations of quasiparticles remains largely unexplored, both theoretically and experimentally. We have investigated the effects of quantum fluctuations of quasiparticles on the operation of RF-SETs for large values of the quasiparticle cotunneling parameter alpha = 8EJ/Ec, where EJ and Ec are the Josephson and charging energies. We find that, for alpha > 1, sub-gap RF-SET operation is still feasible despite quantum fluctuations that wash out quasiparticle tunneling thresholds. Such RF-SETs show linearity and signal-to-noise ratio superior to those obtained when quantum fluctuations are weak, while still demonstrating excellent charge sensitivity. We have operated a QPC charge detector in a radio frequency mode that allows fast charge detection in a bandwidth of several megahertz. The noise limiting the sensitivity of the charge detector is not the noise of a secondary amplifier, but the non-equilibrium device noise of the QPC itself. The noise power averaged over a measurement bandwidth of about 10MHz around the carrier frequency is in agreement with the theory of photon-assisted shot noise. Frequency-resolved measurements, however show several significant discrepancies with the theoretical predictions. The measurement techniques developed can also be used to investigate the noise of other semiconductor nanostructures such as quantum dots in the Kondo regime. A study of the noise characteristics alone can not determine whether the device is operating at the quantum limit; a characterization of back action is also necessary. The inelastic current through a double quantum dot system (DQD) is sensitive to the spectral density of voltage fluctuations in its electromagnetic environment. Electrical transport studies on a DQD system electrostatically coupled to an SET shows qualitative evidence of back-action of SET. The design and fabrication of a few electron DQD device with integrated RF-SET and QPC charge sensors for the study of back action of the sensors and real-time electron dynamics in the DQD are also discussed.

Resonant X-ray scattering has been observed in lanthanides and actinides. The observed scattering is sensitive to magnetization, but it arises primarily from electric, rather than magnetic, multipole transitions. The magnetic sensitivity is due to "exchange" effects and to spin-orbit correlations in one or both of the levels involved in the resonance. "Exchange" effects include the exclusion principle, which permits transitions only to vacant orbitals in partially filled shells, and exchange splitting in band states. The elastic scattering amplitude contains terms dependent on the direction of the magnetic moment up to quadratic order for E1 transitions and up to quartic order for E2 transitions. In coherent scattering of X-rays from spiral antiferromagnets, the magnetic sensitivity results in the formation of resonant magnetic satellites associated with the Bragg peaks. This effect provides a new type of probe for the investigation of magnetic structures.

We are studying the charge transfer in atom-surface scattering using a recently developed many-body theory. The final population of the atom is studied as a function of the surface workfunction, which has a strong effect on the final population. The effects caused by degeneracy, surface bandwidth and velocity are investigated. The formation of the Kondo peak, strongly controls both the initial population and the rate of charge transfer, and consequently the final population. The results show a strong degeneracy and velocity dependence for both the positive and negative ion. For the negative ion we also find a significant bandwidth dependence.

Spin-sensitive electron spectroscopies were used to study paramagnetic metal surfaces and thin films. In these experiments, a beam of low-energy spin-polarized electrons from a GaAs source is directed at the target surface, and the spin polarizations and the energy distributions of scattered electrons are measured by a compact Mott polarimeter equipped with either a retarding field analyzer or a concentric hemispherical analyzer. Secondary electrons ejected from a Cu(100) surface by a polarized incident beam of energies 14, 50 and 100 eV were investigated by spin-polarized secondary electron spectroscopy. The data are interpreted in terms of the fractional contributions of rediffused primary and true secondary electrons to the total secondary electron yield. Spin-polarized electron-energy-loss spectra were obtained from Cu(100) and Mo(110). The data reveal strong evidence for inelastic spin-flip exchange scattering due to electron-hole pair excitation. In particular, a prominent polarization-loss feature evident in the Mo(110) data correlates with the joint density of occupied and unoccupied states. The dramatically different behavior in the polarization of scattered electrons from molybdenum and copper was employed as a signature to determine the attenuation length for low energy electrons in molybdenum. When molybdenum thin films were grown on a Cu(100) substrate, the Mo loss feature becomes prominent upon deposition of only one monolayer.

Spin-polarized electron energy loss spectroscopy (SPEELS) has been used to investigate several paramagnetic surfaces. In this technique, a low energy beam of spin-polarized electrons from a GaAs source is directed at the surface to be studied and the spin-polarization of the emitted electrons, as well as the kinetic energy distribution, is measured via a micro-Mott polarimeter equipped with a retarding potential energy analyzer. The near-elastic-energy electrons contain information on the inelastic scattering channels available in the solid. The spin-polarization of these same electrons is sensitive to the shape of the final state manifold, i.e., the density of unoccupied states. The low energy and behavior of the spin-polarization spectrum mainly reflects the high number of unpolarized electrons present near zero kinetic energy. Results from Cu(100), polycrystalline Au, GaAs(110), GaAs(100) and Mo(110) surfaces suggest that exchange scattering with spin-flip is ubiquitous for the lowest energy electron beam energies studied ($\sim$14 eV). A simple convolution of the empty and occupied densities of states correctly predicts the shape of the energy dependent spin-flip rate.

Metastable (Atom) De-excitation Spectroscopy (MDS) provides a powerful technique with which to investigate surface electronic structure with extreme surface specificity. In this technique a thermal energy beam of noble-gas metastable atoms is directed at the surface under study and the kinetic energy distribution of ejected electrons that result from metastable atom de-excitation is measured. Although the measured distribution contains information about the electronic structure of the outermost surface layer, its detailed analysis requires knowledge of the dynamics of the metastable atom-surface interaction. In the present work, these dynamics have been investigated directly by use of spin-labeling techniques. The electron spins of the incident metastable atoms are polarized and the spin-polarization of the ejected electrons is measured with a Mott polarimeter. Energy resolve electron spin-polarization measurements are reported for a variety of sub-monolayer coverages of cesium on a Cu(100) surface, and for oxygen and cesium co-adsorption on a Cu(100) surface. The Cs/Cu(100) system exhibits large ($\sim$2.8 eV) change in the surface work function. The results of the current work suggest that MDS interactions in both high and low work function regimes are more complex than has previously been supposed. Several additional interactions are suggested to explain the data acquired. The question of the occupancy of the adsorbed cesium valence level at various coverages is also addressed.

Spin sensitive electron spectroscopies were used to study low energy electron inelastic scattering from metal surfaces and thin films. In these experiments, a beam of spin polarized electrons from a GaAs source is directed on the sample surface, and the spin polarization and intensity are measured as a function of energy loss and scattering angle by a Mott electron polarimeter coupled with a concentric hemispherical energy analyzer. Systematic studies of the angular dependence of inelastically scattered electrons were conducted on a Cu(100) surface, and Mo/Cu(100), non-magnetized Fe/Cu(100), and Co/Cu(100) films. The polarization and intensity of scattered electrons were measured as function of energy loss and scattering angle. Further studies were also conducted on Ag(100) surface and amorphous Cu/Ag(100) films. From the experimental results, the angular distributions of dipole and impact scattered electrons can be determined individually and both are found to peak in the specular scattering direction. Preliminary studies were conducted on magnetized Co/Cu(100) films. The spin dependent scattering intensity asymmetry was measured, with a clearly observable peak at energy loss of $\sim$1 eV, which coincides with the band splitting. The polarizations of secondary electrons produced by an unpolarized primary beam were also measured. The polarizations can be related to the band polarization of magnetized cobalt films.

We have investigated the dynamics of the isotropic N-vector model with long-range exchange couplings in random magnetic fields using a 1/N expansion. The leading order is exactly solved, showing the existence of a ferromagnetic phase separated from the disordered paramagnetic phase by a line. The critical behaviour of the system has been examined in the next-to-leading order of the 1/N expansion, showing that the critical exponents are by no means related to the ones of the pure system in d-2 dimensions. The ordered phase has been also investigated in the next-to-leading order, revealing a typical Goldstone behaviour of the non time-persistent part of the transverse fluctuations. For the longitudinal fluctuations, two different types of coexistence singularities emerge, one from the non time-persistent (as in the pure systems), vanishing with the temperature, and a more divergent one from the time-persistent part of the correlation.

Spin-polarized electron energy-loss spectroscopy has been used to investigate the probing depth of low energy ($\sim$30 eV) electrons in metals. A beam of spin-polarized electrons is directed at the surface of the sample and the polarization of the scattered electrons is measured as the function of inelastic energy loss. Different polarization loss features were observed from Cu(100) and Mo(110). By depositing thin molybdenum (copper) films on a Cu(100) (Mo(110)) substrate and observing the appearance (disappearance) of the molybdenum polarization loss feature, it is found that the probing depth in molybdenum is small ($\sim$1 monolayer), but is significantly larger in copper ($\sim$3 monolayers). This difference can be explained by the differences of the joint density of states available for electron-hole pair excitation. The growth mode of Fe/Cu(100) has also been studied by using this method.