Dynamic spin-polarized resonant tunneling in magnetic tunnel junctions.

Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schrödinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.

Optical constants of in situ-deposited films of important extreme-ultraviolet multilayer mirror materials.

We have performed angle-dependent reflectance measurements of in situ magnetron sputtered films of B(4)C, C, Mo, Si, and W. The Fresnel relations were used to determine the complex index of refraction from the reflectance data in the region of approximately 35-150 eV. In the cases of Si, C, and B(4)C we found excellent agreement with published data. However, for Mo and W we found that the optical properties from 35 to 60 eV differed significantly from those in the literature.

Survey of Ti-, B-, and Y-based soft x-ray-extreme ultraviolet multilayer mirrors for the 2- to 12-nm wavelength region.

We have performed an experimental investigation of Ti-, B(4)C-, B-, and Y-based multilayer mirrors for the soft x-ray¿extreme ultraviolet (XUV) wavelength region between 2.0 and 12.0 nm. Eleven different material pairs were studied: Ti/Ni, Ti/Co, Ti/Cu, Ti/W, B(4)C/Pd, B/Mo, Y/Pd, Y/Ag, Y/Mo, Y/Nb, and Y/C. The multilayers were sputter deposited and were characterized with a number of techniques, including low-angle x-ray diffraction and normal incidence XUV reflectometry. Among the Ti-based multilayers the best results were obtained with Ti/W, with peak reflectances up to 5.2% at 2.79 nm at 61° from normal incidence. The B(4)C/Pd and B/Mo multilayer mirrors had near-normal incidence (5°) peak reflectances of 11.5% at 8.46 nm and 9.4% at 6.67 nm, respectively, whereas a Y/Mo multilayer mirror had a maximum peak reflectance of 25.6% at 11.30 nm at the same angle. The factors limiting the peak reflectance of these different multilayer mirrors are discussed.

Mo/Y multilayer mirrors for the 8-12-nm wavelength region.

Mo/Y multilayer mirrors were deposited by dc magnetron sputtering under different deposition conditions. They were characterized by reflectance measurements at normal and grazing angles of incidence, by transmission electron microscopy, and by Auger depth profiling. Normal-incidence peak reflectances of 34% and 22% were measured at wavelengths of 11.5 and 8.1 nm, respectively. Interface roughness and contamination of the layers during deposition limit the peak reflectance of these Mo/Y mirrors.

Mo/Y multilayer mirrors for the 8-12-nm wavelength region.

Mo/Y multilayer mirrors were deposited by dc magnetron sputtering under different deposition conditions. They were characterized by reflectance measurements at normal and grazing angles of incidence, by transmission electron microscopy, and by Auger depth profiling. Normal-incidence peak reflectances of 34% and 22% were measured at wavelengths of 11.5 and 8.1 nm, respectively. Interface roughness and contamination of the layers during deposition limit the peak reflectance of these Mo/Y mirrors.

Si/B(4)C narrow-bandpass mirrors for the extreme ultraviolet.

We report the results of extreme-ultraviolet reflectance measurements and structural characterization of multilayer mirrors made by sequential sputter deposition of Si and B(4)C. Compared with Si/Mo multilayers, Si/B(4)C have a much narrower bandpass (deltalambda) and better off-peak rejection but lower peak reflectance (R(0)). Mirrors with three different designs gave the following results: R(0) = 0.275 and deltalambda = 0.31 nm at 13.1 nm and normal incidence; R(0) = 0.34 and deltalambda = 1.1 nm at 18.2 nm and 45 degrees ; and R(0) = 0.30 and deltalambda = 2.0 nm at 23.6 nm and 45 degrees . These multilayers exhibited excellent stability on annealing at temperatures up to 600 degrees C.

Agranulocytosis secondary to methimazole therapy: report of two cases.

Seventy-three cases of thyrotoxicosis were treated at Lloyd Noland Hospital with methimazole, propylthiouracil or both. Two cases of agranulocytosis occurred (2.7%) secondary to methimazole. Both responded to hospitalization, reverse isolation, and antibiotic coverage with complete recovery of the peripheral blood picture. The toxicity of methimazole is noted. The need for careful monitoring of blood counts during therapy and immediate discontinuance of the drug at the first clinical sign of granulocytopenia is stressed.