Material quality characterization of CdZnTe substrates for HgCdTe epitaxy

Cd1-xZnxTe (CZT) substrates were studied to investigate their bulk and surface properties. Imperfections in CZT substrates affect the quality of Hg1-xCdxTe (MCT) epilayers deposited on them and play a role in limiting the performance of infrared (IR) focal plane arrays. CZT wafers were studied to investigate their bulk and surface properties. Transmission and surface x-ray diffraction techniques, utilizing both a conventional closed-tube x-ray source as well as a synchrotron radiation source, and IR transmission microspectroscopy, were used for bulk and surface investigation. Synchrotron radiation offers the capability to combine good spatial resolution and shorter exposure times than conventional x-ray sources, which allows for high-resolution mapping of relatively large areas in an acceptable amount of time. Information on the location of grain boundaries and precipitates was also obtained. The ultimate goal of this work is to understand the defects in CZT substrates and their effects on the performance and uniformity of MCT epilayers and then to apply this understanding to produce better infrared detectors

Ceramic process and plant design for high-level nuclear waste immobilization

In the last 3 years, significant advances in ceramic technology for high-level nuclear waste solidification have been made. Product quality in terms of leach-resistance, compositional uniformity, structural integrity, and thermal stability promises to be superior to borosilicate glass. This paper addresses the process effectiveness and preliminary designs for glass and ceramic immobilization plants. The reference two-step ceramic process utilizes fluid-bed calcination (FBC) and hot isostatic press (HIP) consolidation. Full-scale demonstration of these well-developed processing steps has been established at DOE and/or commercial facilities for processing radioactive materials. Based on Savannah River-type waste, our model predicts that the capital and operating cost for the solidification of high-level nuclear waste is about the same for the ceramic and glass options. However, when repository costs are included, the ceramic option potentially offers significantly better economics due to its high waste loading and volume reduction. Volume reduction impacts several figures of merit in addition to cost such as system logistics, storage, transportation, and risk. The study concludes that the ceramic product/process has many potential advantages, and rapid deployment of the technology could be realized due to full-scale demonstrations of FBC and HIP technology in radioactive environments. Based on our finding and those of others, the ceramic innovation not only offers a viable backup to the glass reference process but promises to be a viable future option for new high-level nuclear waste management opportunities

DIPOLE-EXCHANGE SURFACE WAVE DISPERSION AND LOSS FOR A METALLIZED FERRITE FILM

Les courbes de dispersion pour un conducteur sur un film ferromagnétique sont calculées, comprenant les effets de dipôle, échange et de conductivité. Les pertes de conductivité dominent pour fδ ~ 1 tandis que les pertes d'échange sont grandes pour αf2 ≥1, f est la constante de propagation de l'onde de surface, δ est la longueur de peau et α la constante d'échange. La courbe de dispersion de l'onde de surface montre une variété de forme qui dépend des valeurs de δ, α et la proportion δ2/α. Les caractères de la dispersion de l'onde de surface et des pertes sont résumés.The frequency versus wavenumber dispersion for a conductor on an insulating ferromagnetic film is calculated including dipolar, exchange and conductivity effects. Conductivity losses dominate for fδ ~ 1 while propagation losses are largest for αf2 ≥ where f is the surface wave propagation constant, δ the skin depth and α is the exchange constant. The surface wave dispersion curve exhibits a variety of shapes depending upon the values of δ and α and ratio δ2/α. The general features of magnetic surface wave dispersion and loss are summarized

GEOMETRICAL QUANTIZATION AND SHAPE EFFECTS OF SPIN-WAVE MODES

Le spectre de modes déduit de l'approximation des ondes de spin extrapolés au cas limite des grandes longueurs d'onde est comparé aux solutions déduites de l'effet d'échange dipolaire dans le cas de couches minces d'épaisseur finie et de surface infinie (= couche mince infinie). Des résultats de nombreuses expériences d'ondes de spin sont comparés avec le spectre de modes d'une couche mince infinie dans l'hypothèse d'une quantification géométrique. L'accord raisonnablement bon que l'on trouve suggère que la constante de propagation dans le plan de la couche mince est quantifiée par rapport aux dimensions finies de l'échantillon. De petites différences trouvées pour les modes d'ordre bas semblent indiquer qu'il existe quelque divergence par rapport à ce schéma simple de quantification. Des solutions exactes obtenues dans le cas du cylindre elliptique aimanté dans la direction du grand axe sont comparées à celles correspondant au cas d'une plaque infinie aimantée dans une direction parallèle à la surface. On trouve que dans certaines conditions la constante de propagation est quantifiée géométriquement de façon simple. L'effet de la forme géométrique sur la fréquence des ondes de spin est discuté dans le cas du cylindre elliptique, circulaire, de la sphère, du disque et dans le cas de formes intermédiaires.The mode spectrum derived from spin-wave approximation extrapolated to the long wavelength limit is compared with the dipole-exchange solutions for a film of finite thickness with an infinite surface - the infinite film. Experimental results from a number of spin-wave experiments are compared with the mode spectrum of an infinite film with the assumption of geometrical quantization. The reasonably good agreement of such an analysis suggests that the propagation constant in the plane of the film is quantized according to the dimensions of the finite sample. Small discrepancies for the low order modes suggest departures from the simple quantization scheme. Exact solutions for the elliptical cylinder magnetized along the long axis are compared with those of the infinite plate magnetized in a direction paralle1 to the surface. It is found that under certain conditions the propagation constant is geometrically quantized in a simple manner. The effects of shape on spin-wave frequencies as a function of geometry are discussed for the elliptical cylinder, circular cylinder, sphere, disk and intermediate shapes