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A calculation of electron-phonon scattering rates and intersubband optical gain spectra was conducted including the optical phonon confinement effect in AlGaAs/GaAs/AlGaAs quantum well heterostructures was conducted. Results from the comparison of the calculated gain spectra with those calculated using the bulk phonon approximation reveals that details of the phonon spectrum have a strong influence on the intersubband optical gain.

A correlation between data from Mossbauer quadrupole splittings and NMR is helpful in detecting the 57Fe NMR signals for valence electron cloud asymmetry. The 11 197 ppm chemical shift reported in literature for ferrocytochrome, c20, which is based on Mossbauer-NMR correlation, is acceptable. This correlation also indicates chemical shifts of 11 000 to 13 000 ppm for most bis-pyridine and nonhindered imidazole complexes of model heme and cytochrome b5.

The equivalent network approach is useful for the analysis of the scattering problem of guided electron wave obliquely incident on step discontinuities in planar heterostructures. The network specially considers network representations to determine physical pictures of the quantum effects. The network makes possible input admittance formulation with which equations can be derived that determines the scattering and waveguiding of the electron wave obliquely incident on step discontinuities. Numerical examples for a three-layered electron waveguide with a stub are given.

An ensemble Monte Carlo method helps evaluate the photoexcited electron-hole pairs' dynamics in Ge and reveals the scattering of electrons from the optically coupled area through the Lambda and Xi valleys to the L valleys. This relaxation of electrons causes the holes to be predominant in the nonlinear absorption spectra. At 1.5 eV photoexcitation, distortion of the band-structure leads to enhanced contribution by the holes to the pump energy transient.

Systems such as Co/Cu/Ni(Fe) multilayers, AgCo granular alloys and intermetallics show giant magnetoresistance (GMR), which is verified by their Hall effect, thermal conductivity, magnetoresistance and thermoelectric power comparisons. Transport properties indicate the variation or similarity in the conduction-electron scattering of these systems. The GMR effect in intermetallic compounds does not depend on the two-dimensional ferromagnetic layers or itinerant magnetic electrons.

Analysis of the influence of antiphase boundaries on the electrical features of InP/Si layers shows that electron scattering depends on the development of antiphase boundaries (APBs) while dislocation densities are independent of antiphase domains (APDs). The temperature dependency of free-electron levels in the layers is sensitive to a deep donor in the 77 to 300 K temperature range. The degree of epitaxial layer compensation and the space-charge density in the layers vary with APB density, while local stress affects APB in the layers.

A series of positive delta functions helps simulate the longitudinal (rho(xx)) and Hall (rho(xy)) resistivities for a two-dimensional square array of scatterers. For systems with strong potential strength rho(xy) can be negative and quenched while rho(xx) exhibits commensurate oscillations. Impurities influence only rho(xx). Numerical results explain the influence of lattice, impurity scattering and electron density on the quenching of Hall effect and commensurate oscillations.

Measurements performed near the junctions of the interfaces of Al/SiO2/Si heterostructures reveal the presence of weak features in the energy loss spectra. The measurements enable the development of a four-layered energy loss spectra model. The model is capable of explaining the distribution of electric potential in the heterostructure and also facilitates the calculation of inelastic scattering probability curves for the Al/SiO2/Si heterostructure.

Simple monotonic equations yield differential and total electron/atom elastic scattering cross sections for normal incidence in the range 0.1 to 0.3 kev obtained from Mott scattering cross sections based on total scattering cross section, Rutherford screening parameter and the screened to isotropic Rutherford cross section ratio. The elastic cross sections predict backscattering cross sections that exhibit monotonicity with atomic number increase and defy the periodicity of atomic models. The model represents the scattering of the electrons in a solid as a multiple scattering process.

Monte Carlo calculations, based on electron inelastic scattering models, enable the analysis of energy distributions of low-energy back-scattered electrons in Si, Cu and Au. Dielectric functions describe the shape of EN(E) spectra in Cu and Au. Electrons produced from L-shell ionization identify the characteristic hump in Si, which occurs at energies greater than 100 eV.

A study of giant magnetoresistance in MBE-grown Co-Cu superlattices revealed that low structure dimensionality improved scattering of conduction electrons from paramagnetic interfaces. This enhanced scattering was in accordance with Langevin-like saturation value obtained at high fields. Spin-dependent density of states caused magnetotransport behavior at the Co-Cu interfaces.

Exoelectron spectroscopy facilitated the study of structural imperfection in amorphous silicon, especially on the a-Si:H system. Heat- and light-modified changes associated with diffusion of atomic particles such as hydrogen and the annealing and electronic structure of defects were observed. The method employed was the registering photothermostimulated exoelectron emission.

Application of the Boltzmann transport theory to thin single crystal films of defect-and-impurity free metals with suitable electron scattering boundary conditions, reveals a reduction in thermal conductivity as a result of boundary scattering. Thin films which are nearly 50 times thicker than the mean free path are affected in the presence of grain boundary scattering.

The atomic number of the sample atoms influences the high angle elastic scattering of electrons in scanning transmission electron microscopy, and square of the atomic number influences the cross-section of Rutherford scattering. The coherent effects of scattering and diffraction are eliminated by the scattered electrons at high angles over large angular ranges of 75 to 150 milliradians. The coherent scattering is effective when a fine electron probe is issued on perfectly crystalline materials.

The experimental thermal wave images of planar subsurface defects are inverted to determine an enhanced representation of the shape and size of planar subsurface defects. The inversion is effected by an algorithm. The inversion algorithm can also be used in the improvement of the spatial resolution of such defects. The calculations are performed on Macintosh IIfx computers for 128 by 128 pixel images. The inversion time is 1 minute or less.

Oscillatory behavior with magnetic field is revealed by numerical evaluation of electron scattering rates, due to reaction with interface phonon modes in semiconductor GaAs/GaAlAs quantum wells in a quantizing magnetic field. Enhancement in the width of the well reduces the scattering rate. This is not the case with bulk confined phonons.

The X-band electron quantum interference and its movement through virtual state occurs in Al(x)Ga(1-x)As/AlAs/Al(x)Ga(1-x)As/AlAs/Al(x)Ga(1-x)As heterostructures, where x = 0.5, 0.42 and 0.45. The scattering rate for X-band electrons at 25k is 1. 13 times 10 to the 12th power per second, when x = 0.5. The scattering rate is 8.75 times 10 to the 11th power per second at 15 K, when x = 0.45. Electron-electron and X-intervalley scattering is observed, when x = 0.42 at 8. 2K.

It has been shown that, in some solid-state systems, electrons with energies close to the Fermi level behave quasi-atomically. X-ray absorption and electron-energy-loss spectroscopy involving the excitation of core electrons to empty electronic states can then be classified by initial and final states described by L, S and J quantum numbers, and allowed transitions that follow strict atomic selection rules. These ideas are illustrated for 4d arrow to the right 4f transitions of Ba in high-T(sub c) superconductors, 2p arrow to the right 3d transitions of Ca2+ in CaF2, 4f(super 7)-4f(super 7) transitions in Gd metal, and X-ray dichroism of 3d-4f transitions in Dy. Such effects are compared with situations where the electrons are band like in behaviour and where electron correlations take more complex forms.

For the first time, researchers watch as a knot formed from an ultra-cold gas decays, forming a vortex. For the first time, researchers watch as a knot formed from an ultra-cold gas decays, forming a vortex., Author Affiliations: A structure known as a quantum knot (artist's impression) untangles itself into a vortex. Credit: Heikka Valja The quantum knot (artistically depicted) untangles into a vortex over its [...]

Monte Carlo simulations were used to study the mobility and steady state velocity-field properties of electron transport in mercury cadmium telluride. Results show an increase in the screening length as the electric field increases, a dependence more predominant in low carrier concentrations. Degeneracy effects along with the screening length dependence on the distribution function were also found to affect electron mobilities and drift velocities despite low carrier concentrations.

A semi-empirical model is introduced for Monte Carlo simulation of surface scattering in the silicon inversion layer of metal oxide semiconductor field effect transistors. The model, which describes both diffusive and specular scattering, is used in a comparison of experimental data acquired from devices of different electric fields, channel dopings and substrate bias. Its performance, as compared to the drift-diffusion simulator, is also discussed.

These are summaries of some of the many papers presented at the 2006 IMS Conference and Meeting in Chicago. The article also shows some of the entries in the IMS […]

The contribution of conduction electron scattering to magnon relaxation in Permalloy thin films [2-20 nm] was studied by resistivity measurements and by high frequency permeability measurements using network analyzer ferromagnetic resonance. Both effective Gilbert damping [alpha] of the magnetization and electrical resistivity p were measured from room temperature down to 10 K. We observe what an increase of the resistivity does not necessarily lead to an increase of the effective damping. Indeed, increases up to 50% of the resistivity in the studied temperature range are not accompanied by any change of the damping parameter [alpha]. We discuss our findings by sorting out the different conduction electron scattering channels that lead to spin-flip, and that hence contribute to the overall damping. We conclude that alloy disorder scattering is the main channel that leads to correlated contributions to damping and resistivity. Index Terms--Damping, magnetization, thin films.

We have developed a new type of field-expansion spectrometer to measure the neutron beta decay correlations (a, b, B, and A). A precision measurement of these correlations places stringent requirements […]

A key requirement for spin valves (SV) with nano-oxide layers (NOL) are the formation of the smooth and uniform interface between NOL and magnetic layer for specular electron scattering. We investigated the natural oxidation conditions using mixed gases ([O.sub.2]/[N.sub.2] and [O.sub.2]/Ar) for the uniform NOL formation in specular SVs. We have compared the magnetoresistance (MR) properties and thermal stability of SVs with NOL formed in mixed gases with those formed using pure [O.sub.2]. We can optimize oxidation conditions using mixed gases for enhanced MR ratio and reduced interlayer coupling field. Index Terms--Nano-oxide layer, specular scattering, spin valve.

Interlayer diffusion, thermal stability, and specular scattering behaviors of spin-valves (SV) where CoNbZr films were employed in as under and capping layers have been investigated. CoNbZr 2 (or Ta 5)/CoFe/Cu/CoFe/IrMn/CoNbZr 0~10 (or Ta 5) nm stacks were sputter-deposited on Si/Si[O.sub.2] substrates. Both normalized MR ratio and exchange bias field ([H.sub.ex]) of a conventional Ta-based SV decreased monotonically about 50% upon exposure to postdeposition annealing at 300[degrees]C. On the contrary, these values increased about 50% for CoNbZr-based SVs, in particular, as CoNbZr capping thickness was less than 4 nm. Surface depth profiling results suggest that Mn diffused into the pinned CoFe layer (inward) but not into the Ta capping layer (outward) for the Ta-based SV. Unlike in the Ta capping case, a CoNbZr capping layer promoted outward Mn diffusion resulting in a formation of thin Mn-oxide layer at the surface. We attribute the increase of MR ratio in CoNbZr-capped SVs to enhanced specularity due to the presence of thin Mn-oxide. However, the specular scattering effect is reduced by increasing the thickness of CoNbZr capping layer. Index Terms--Amorphous CoNbZr, specularity, spin valves, thermal stability.

The injection of spin-polarized electrons from ferromagnetic contacts into multi-walled carbon nanotubes provides direct evidence for the coherent transport of electron spins. A hysteretic magnetoresistance is observed in several nanotubes, and it is estimated that the spin-flip scattering length is at leas 130 nm.

A study is conducted on the swarm parameters in carbon tetrafluoride (CF4) using the Monte Carlo method. Results show that swarm parameter errors caused by the isotropic scattering assumption are high for low and middle values of electric field to gas density ratios. This is attributed to the fact that collisions with excitation of vibrational states exceed the elastic collisions in the vicinity of the Ramsauer minimum.

Ultrahigh-peak-power lasers provide a way of creating large photon densities needed to study relativistic or nonlinear Thomson scattering. Such an approach has been used to provide experimental confirmation of the theoretical predictions of relativistic Thomson scattering. A future goal is to achieve coherent harmonics generation, which could be used in table-top X-ray sources.

By inserting only 0.75 nm-thick Cu layer between the CoFe/Cu/CoFe/IrMn spin-valve stack and Ta underlayer, magnetoresistance (MR) ratio and AR were about 1.8 and 1.4 times, respectively, as large as those without the Cu layer. Atomic force microscopy, x-ray diffraction, and MR measurements suggest that the Cu 'islands' formed in the initial growth stage modified the interfaces of the spin-valve and the structure of the component layers, resulting in the enhancement of the spin-dependent electron scattering. When the inserting Cu thickness (t) was larger than 1.5 nm, not only the MR characteristics but the magnetic properties, such as coercivity of the free layer, was improved in comparison with that of t = 0 nm. This is due to the considerable increase in the crystallinity of the spin-valve films. In this thickness range, Cu is expected to function as the buffer 'layer'. Index Terms - Cu islands, spin-valve, GMR, coercivity

Specular scattering of electrons at the top surface of bottom spin valves has been found to contribute to the giant magnetoresistance effect. The specular scattering can be increased by the deposition of [approximately]2 monolayers (ML) of Au, Ag, or Cu, with the result that the GMR increases and the [Mathematical Expression Omitted] decreases. The deposition of 2 ML of species that disorder the surface, such as Ta, Si, C, or [Ni.sub.80][Fe.sub.20], suppresses the specular scattering. This suppression appears to be useful as a new method for evaluating the importance of specular scattering.

The scanning tunneling microscope (STM) has been used to observe threefold symmetric electron scattering from point defects on a graphite surface. These theoretically predicted electronic perturbations could not be observed with a bare metal tip but could only be imaged when a fullerene ([C.sub.60]) molecule was adsorbed onto the tunneling region (apex) of an STM tip. Functionalizing an STM tip with an appropriate molecular adsorbate alters the density of states near the Fermi level of the tip and changes its imaging characteristics., The STM has recently enabled scientists to image local surface electronic phenomena on the nanometer scale. On metal surfaces, the STM has been used to image scattering of surface-state electrons [...]

The excitation of a relativistic plasma wave to the breaking point by a short and high-intensity laser pulse, using the Raman forward-scattering instability, accelerates the electrons and enhances their number. The acceleration of electrons causes a number of scattered frequencies and the coherence of laser light scattered by the wave is lost. An increase in plasma density increases the maximum electron energy (up to 44 MeV) and results in a tremendous broadening of each anti-Stokes peak at the corresponding high density.

Computation of triple electron scattering rates of triple collisions of two electrons and one charged impurity in a nondegenerate electron gas confined in a single mode quantum wire reveals that electron temperature relaxation time of triple collisions is similar to momentum relaxation time. Triple collision time is smaller than electron-impurity momentum relaxation time in remote impurity doping.

Standing-wave patterns in electron density, observed through scanning tunnelling microscopic (STM) studies of noble metal surface, are due to the scattering of surface electrons from small arbitrarily placed impurities in a two-dimensional system. Standing-waves of particular geometries can be produced using quantum corrals, which are specific enclosed structures of atoms assembled together. STM images of corral walls reveal that iron with atoms submerge the electron wave amplitude and produce black dots on the copper surface which limits the collective behavior of artificial nanostructures.