Electromigration theory unified

The starting formula of Bosvieux and Friedel for the force on an ion in a metal due to an applied voltage is shown to lead to the same description as the linear-response approach used in the field since its introduction by Kumar and Sorbello. By this electromigration theory has become a unified theory. It follows after accounting for a treacherous trap term, which at first sight seems to be zero. Up to now Bosvieux and Friedel claimed to predict a completely screened direct force, which means that only a wind force would be operative. In addition the amount of screening has been calculated up to second order in the potential of the migrating impurity, using a finite temperature version of the screening term derived by Sham. For a proton in a metal modeled as a jellium the screening appears to be about 15%, which is neither negligible nor reconcilable with the old full-screening point of view.Comment: 6 pages, 1 figur

The Electromigration Force in Metallic Bulk

The voltage induced driving force on a migrating atom in a metallic system is discussed in the perspective of the Hellmann-Feynman force concept, local screening concepts and the linear-response approach. Since the force operator is well defined in quantum mechanics it appears to be only confusing to refer to the Hellmann-Feynman theorem in the context of electromigration. Local screening concepts are shown to be mainly of historical value. The physics involved is completely represented in ab initio local density treatments of dilute alloys and the implementation does not require additional precautions about screening, being typical for jellium treatments. The linear-response approach is shown to be a reliable guide in deciding about the two contributions to the driving force, the direct force and the wind force. Results are given for the wind valence for electromigration in a number of FCC and BCC metals, calculated using an {\it ab initio} KKR-Green's function description of a dilute alloy.Comment: 14 pages, 1 Postscript figur

Giant phase-conjugate reflection with a normal mirror in front of an optical phase-conjugator

We theoretically study reflection of light by a phase-conjugating mirror preceded by a partially reflecting normal mirror. The presence of a suitably chosen normal mirror in front of the phase conjugator is found to greatly enhance the total phase-conjugate reflected power, even up to an order of magnitude. Required conditions are that the phase-conjugating mirror itself amplifies upon reflection and that constructive interference of light in the region between the mirrors takes place. We show that the phase-conjugate reflected power then exhibits a maximum as a function of the transmittance of the normal mirror.Comment: 8 pages, 3 figures, RevTe

Analysis of side writing asymmetry

The side writing asymmetry of a recording head was investigated using an overwrite configuration that enhances the edge effects. The track profiles of the overwrite patterns were measured for analyzing the side writing performance of the head. Magnetic force microscope (MFM) images of the overwrite patterns were studied using fast Fourier transforms (FFT), and they confirmed the profiling results. We measured weak edge effects at good pole alignment. The experiments were performed with metal evaporated (ME) and metal particle (MP) tapes having magnetic layers between 50 and 300 nm

Domain studies of CoCr with perpendicular anisotropy

R.F. Magnetron sputtered CoCr films (79/21 at%) with various thicknesses are magnetically characterized. The domain structure is observed by digitally enhanced Kerr microscopy and depends on the Hc/Hk values of the samples. For low and high coercivity films a comparison is made between the measured VSM hysteresis, domain period and a theoretical domain model. The domain shape is a function of the magnetic history of the sample and the bending created by the deposition process

Andreev States in long shallow SNS constrictions

We study Andreev bound states in a long shallow normal constriction, which is open to a superconductor at both ends. The interesting features of such setup include the absence of electron-hole symmetry and the interference of electron waves along the constriction. We compare results of a numerical approach based on the Bogoliubov equations with those of a refined semiclassical description. Three types of Andreev bound states occur in the constriction: {\it i}) one where both electron and hole wave part of the bound state propagate through the constriction, {\it ii}) one where neither electron nor hole wave part propagate, and {\it iii}) one where only the electron wave propagates. We show that in a wide energy region the spacing between the Andreev states is strongly modulated by the interference of electron waves passing the constriction

Model calculations of the proximity effect in finite multilayers

The proximity-effect theory developed by Takahashi and Tachiki for infinite multilayers is applied to multilayer systems with a finite number of layers in the growth direction. The purpose is to investigate why previous applications to infinite multilayers fail to describe the measured data satisfactorily. Surface superconductivity may appear, depending on the thickness of the covering normal metallic N layers on both the top and the bottom. The parameters used are characteristic for V/Ag and Nb/Pd systems. The nucleation process is studied as a function of the system parameters.Comment: 12 pages, 15 figures, RevTe

Method and Apparatus for Detecting Microorganisms Within a Liquid Product in a Sealed Vial

An apparatus and method are provided for the noninvasive and nondestructive detection of microorganisms within a liquid product contained within a sealed vial. The apparatus includes a near-IR light source that produces both incident and reference beams having a wavelength between 800 and 2500 nm and, more preferably, 1100 and 1360 nm. The apparatus also includes an integrating sphere having incident and reference beam ports and a sample window opposite the incident beam port. A detector is mounted in the integrating sphere substantially adjacent the sample window. A substantially U-shaped mirror is provided to hold the vial. The U-shaped mirror is of a size substantially corresponding to the diameter of the vial. In operation, the incident beam is directed through a sample window so as to enter the vial adjacent a sidewall of the mirror. In this way the U-shaped mirror reflects the incident beam so that it passes through the vial three times before returning to the detector. A computer analyzes the resulting signals from the detector

Method and System for In Situ Spectroscopic Evaulation of an Object

A method and system for spectroscopically determining surface and product characteristics is employed for rapid detection of product characteristics and/or the presence or absence of suspected analytes, and the concentration of the analyte. The method and system uses a signal wide band detector that does not require focusing optics in many environments. It can be used for cleaning validation of pharmaceutical products and process equipment