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Optical properties of n-doped (Si) hexagonal Ga1-xMnxN films (x=0.015) grown by metal-organic chemical-vapor deposition (MOCVD) on c-plane sapphire substrates have been studied by infrared reflectance spectroscopy. The effect of free carriers on GaMnN optical phonons, namely E1(LO) and E1(TO), is explored. It is found that the frequency of E1(LO) increases with increasing free carrier concentration. The absorption coefficient (α) is calculated for the 200-2000 cm-1 range and the maximum value of α is found to be ∼105 cm-1 at a frequency of 560 cm-1. With increasing free carrier concentration, the FWHM of the absorption peak increased by 35%-40% as compared to an unintentionally doped (<1×1016 cm-3) film. [ABSTRACT FROM AUTHOR]

Spontaneous transient outward K+ currents (STOCs) elicited by Ca2+ sparks and steady-state K+ currents modulate vascular reactivity, but effects of artery size. diabetic dyslipidemia, and exercise on these differentially regulated K+ currents are unclear. We studied the conduit arteries and microvessels of male Yucatan swine assigned to one of three groups for 20 wk: control (C, n = 7), diabetic dyslipidemic (DD. n = 6), or treadmill trained DD animals (DDX, n = 7) Circumflex artery blood flow velocity obtained with intracoronary Doppler and lumen diameters obtained by intravascular ultrasound enabled calculation of absolute coronary blood flow (CBF) Ca2+ sparks were determined in pressurized microvessels, and perforated patch clamp assessed K+ current in smooth muscle cells isolated from conduits and microvessels. Baseline CBF in DD was decreased versus C In pressurized microvessels. Ca2+ spark activity was significantly lower in DD versus C and DDX (P < 0.05 vs. DDX). STOCs were pronounced in microvessel (∼35 STOCs/min) in sharp contrast to conduit cells (-∼2 STOCs/min), STOCs were decreased by 86% in DD versus C and DDX in microvessels: in contrast, there was no difference in STOCs across groups in conduit cells Steady-state K+ current in microvessels was decreased in DD and DDX versus C; in contrast. sleady-state K+ current in conduit cells was decreased in DDX versus DD and C, We conclude that steady-state K+ current and STOCs are differentially regulated in conduit versus microvessels in bealth and diabetic dyslipidemia. Exercise prevented diabetic dyslipidemia-induced decreases in baseline CBF, possibly via STOC-regulated basal microvascular tone. [ABSTRACT FROM AUTHOR]

Laves intermetallics (AB2 compounds) play an important role in the disposal of metallic waste resulting from the electrometallurgical treatment of spent nuclear fuel. These ZrFe2-type intermetallics incorporate and immobilize highly radioactive and long-lived constituents that are present in waste forms based on the stainless steel–zirconium (SS–Zr) alloys. This paper reviews the metallurgy of SS–Zr alloys with emphasis on Laves intermetallic behavior. Microscopy and diffraction studies have shown that all actinide elements and most fission product elements are present only in the ZrFe2-type intermetallics of a stainless steel–15 wt.% zirconium (SS–15Zr) waste form, whereas only molybdenum is incorporated in the ZrFe2-type intermetallics of a zirconium–8 wt.% stainless steel (Zr–8SS) alloy. Because of the importance of material durability to waste disposal, recent experiments have been aimed at determining the corrosion behavior of these intermetallics. Results from transmission electron microscopy of corrosion layers observed on the ZrFe2-type compounds are presented. [Copyright &y& Elsevier]

A GaN/AlGaN heterojunction interfacial work function internal photoemission infrared detector responding in 8–14 and 20–70 μm ranges has been demonstrated. Free carrier absorption based photoresponse shows a wavelength threshold of 14 μm with a peak responsivity of 0.6 mA/W at 80 K under -0.5 V bias. A sharp peak in the 11–13.6 μm range is observed superimposed on the free carrier response. In addition, the work demonstrates 54 μm (5.5 THz) operation of the detector based on 1s–2p± transition of Si donors in GaN. Possible approaches on improving the performance of the detector are also addressed. [ABSTRACT FROM AUTHOR]

The structure and surface bonding configuration of InN layers grown by high-pressure chemical vapor deposition have been studied. Atomic hydrogen cleaning produced a contamination free surface. Low-energy electron diffraction yielded a 1×1 hexagonal pattern demonstrating a well-ordered c-plane surface. High-resolution electron energy loss spectra exhibited a Fuchs–Kliewer surface phonon and modes assigned to a surface N–H species. Assignments were confirmed by observation of isotopic shifts following atomic deuterium cleaning. No In–H species were observed, and since an N–H termination of the surface was observed, N-polarity indium nitride is indicated. [ABSTRACT FROM AUTHOR]

The lattice vibrations of undoped hexagonal Ga1-xMnxN (x from 0.0% to 1.5%) epitaxial films grown on c-plane sapphire substrates by metalorganic chemical vapor deposition have been investigated using infrared reflectance spectra in the frequency region of 200–2000 cm-1 (5–50 μm) at room temperature. The experimental reflectance spectra were analyzed using the Lorentz oscillator model for infrared-active phonon observed. The E1(LO) phonon frequency slightly decreases with increasing Mn composition. However, the E1(TO) phonon frequency linearly increases with the Mn composition, which can be well expressed by (558.7+350x) cm-1 and the broadening values are found to be larger than that of the GaN film. It indicates that Mn incorporation decreases the peak values (from the E1 phonon) of the infrared dielectric functions due to the local variation in the lattice constants and to the destruction of the crystal translational symmetry. [ABSTRACT FROM AUTHOR]

We report pseudodielectric function data 〈ε&rang = (ε[sub a1] + i 〈ε[sub a2]〉 and 〈µ〉 = 〈ε[sub c1]〉 + i 〈ε[sub c2]〉 for the optically uniaxial material ZnGeP[sub 2], critical point energies of structures in these data, and dielectric function data for the natural oxide. Annealing reduces the values of the peaks of 〈ε[sub a2]〉. [ABSTRACT FROM AUTHOR]

Presents a method for the determination of optical constants. Measurement of the Brewster angle and reflectivity of polarized light parallel to the plane of incidence; Consideration of optical constants one and two as a function of photon energy; Evaluation of results obtained on gallium arsenide.

Presents the photoluminescence, photoconductivity and optical absorption of zinc germanium phosphide crystals grown by gradient freezing and high pressure physical vapor transport. Components of optical absorption spectra; Presentation of a model of donor and acceptor related subbands in energy gap; Interpretation of lower absorption upon annealing.

By DTA and x-ray diffraction the phase relations in the pseudobinary system In-CuInS have been investigated. CuInS hs a melting point of 1090° C and within this system there is a broad region of liquid immiscibility. A four phase invariant reaction exists at 633° C which is of the form: L = L+ CuInS + InS. [ABSTRACT FROM AUTHOR]