bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of New Thermoelectrics Using Modulated Elemental Reactants
Authors: Hornbostel Marc D. , Sellinschegg Heike , Johnson David C. 
Published: April 2011

AbstractA series of new, metastable ternary crystalline compounds with the skutterudite crystal structure have been synthesized using modulated elemental reactants. The initial reactants are made up of multiple repeats of a ˜25Å thick unit containing elemental layers of the desired ternary metal, iron and antimony. Low temperature annealing (150°C) results in interdiffusion of the elemental layers to form amorphous reaction intermediates. Annealing these intermediates at temperatures between 200°C and 250°C results in exothermic crystallization of the desired skutterudite crystal structure. Most of the new compounds prepared are only kinetically stable, decomposing exothermically to form thermodynamically more stable mixtures of binary compounds and elements. Low angle x-ray diffraction studies show that the resulting films are exceedingly smooth. These films have an ideal geometry for measuring properties of importance for thermoelectric devices—the Seebeck coefficient and the electrical conductivity. Thermal conductivity can be measured using a modification of the 3ω technique of Cahill. Samples can be produced rapidly, allowing for systematic screening and subsequent optimization as a function of composition and doping levels.
Measurement of the Thermoelectric Properties of Quasicrystalline AlPdRe and AlCuFe Alloys.
Authors: Wilson M.L. , Legault S. , Stroud R.M. , Tritt T.M. 
Published: April 2011

AbstractWe report the measurement of the thermal conductivity, electrical resistivity, and thermoelectric power on two quasicrystalline compounds, A170Pd20Re10 and A162.5Cu25Fe12.5. These materials are found to posses a thermal conductivity of order 1 W/m K, while retaining their semimetallic conductivity. These features coupled with moderately large thermopowers, up to 55 μV/K, imply that the general class of quasicrystalline compounds warrants careful investigation for their potential as new thermoelectric materials.
Electrical Properties and Figures of Merit for New Chalcogenide-Based Thermoelectric Materials
Authors: Schindler Jon L. , Hogan Tim P. , Brazis Paul W. , Kannewurf Carl R. , Chung Duck-Young , Kanatzidis Mercouri G. 
Published: April 2011

AbstractNew Bi-based chalcogenide compounds have been prepared using the polychalcogenide flux technique for crystal growth. These materials exhibit characteristics of good thermoelectric materials. Single crystals of the compound CsBi4Te6 have shown conductivity as high as 2440 S/cm with a p-type thermoelectric power of ≈ +110 μV/K at room temperature. A second compound, β-K2Bi8Se13 shows lower conductivity ≈ 240 S/cm, but a larger n-type thermopower ≈ −200 μV/K. Thermal transport measurements have been performed on hot-pressed pellets of these materials and the results show comparable or lower thermal conductivities than Bi2Te3. This improvement may reflect the reduced lattice symmetry of the new chalcogenide thermoelectrics. The thermoelectric figure of merit for CsBi4Te6 reaches ZT ≈ 0.32 at 260 K and for β-K2Bi8Se13 ZT ≈ 0.32 at room temperature, indicating that these compounds are viable candidates for thermoelectric refrigeration applications.
Non-Destructive and Whole Wafer Characterization of III-V Infrared Epitaxial Materials Prepared by Turbo Disk Metalorganic Chemical Vapor Deposition
Authors: Feng Z. C. , Pelczynski M. , Beckham C. , Cooke P. , Ferguson I. , Stall R. A. 
Published: April 2011

AbstractMultiple wafer growth of infrared III-V semiconductor materials of InSb and InGaAsP have been produced by metalorganic chemical vapor deposition technology employing a vertical reactor growth configuration with a high speed rotating disk. Three measurement techniques of sheet resistivity, Fourier transform infrared (FTIR) reflectance and photoluminescence have been used to characterize epitaxial films on wafers up to 4″ diameter. Mapping distributions of the film thickness, sheet resistivity, surface morphology, and PL peak wavelength with uniformities better than 1% are illustrated. Data from our 2900 runs are produced. Variations of the characteristic features of the film with the growth conditions are discussed. These whole wafer and non-destructive material characterization techniques tightly coupled with the epitaxial processes are necessary to realize the high quality and high uniformity growth of state-of-art materials in a production environment.
High Temperature Infrared Photon Detector Performance
Authors: Grein C. H. , Ehrenreich H. 
Published: April 2011

AbstractThe combined effects of suppressing Auger recombination by band structure engineering strained-layer superlattices (SL), suppressing radiative recombination by photon recycling, and suppressing both Auger and radiative recombination with carrier depletion are calculated quantitatively for long-wavelength and mid-wavelength InAs/ InxGa1-xSb SL-based infrared detectors operating at temperatures between 200 and 300K. The results are compared to their HgCdTe counterparts. The SL performance is better in all cases. However, the carrier concentrations required for typical background limited performance (300K, 2π field of view), ranging between about 1 × 1013 and 4 × 1013 cm−3 at 300K in long-wavelength to mid-wavelength SLs, are seen to be impractically low. The carrier concentration in a 11 μm photon detector yielding equivalent performance to an ideal 300K thermal detector is about 1014 cm−3. Large performance enhancement using carrier depletion therefore appears impractical even in optimized SLs.
New Type of ir Photodectors Based on Lead Telluride and Related Alloys
Authors: Khokhlov D. R. 
Published: April 2011

AbstractDoping of the lead telluride and related alloys with the group III impurities results in an appearance of the unique physical features of a material, such as such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We review the physical principles of operation of the photodetecting devices based on the group ifi-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group IIIdoped IV-VI in comparison with the modem photodetectors are summarized.
Active Anti-Guide Vertical Cavity Surface Emitting Lasers with Diffused Quantum Wells Structure
Authors: Yu S. F. , Li E. Herbert , Man W. M. 
Published: April 2011

AbstractThe enhancement of single transverse mode operation in vertical cavity surface emitting lasers by using interdiffused quantum wells is proposed and analyzed. It is observed that the influence of self-focusing (arising from carrier spatial hole burning and thermal lensing) on the profile of transverse modes can be minimized by introducing a step diffused quantum wells structure inside the core region of quantum-well active layer. Stable single-mode operation in vertical cavity surface emitting lasers can also be maintained.
Second-Harmonic and Sum-Freqency Generation in CdGeAs2
Authors: Tanaka Eiko , Kato Kiyoshi 
Published: April 2011

AbstractCdGeAs2 has been found to be phase-matchable for type-2 SHG down to 2.833 μ m and type-2(b) SFG between the fundamental and second harmonic of a CO2 laser down to 10.4406 μ m at 20.0°C. The Sellmeier's equations and the thermo-optic dispersion formula which reproduce well the phasematching properties of SHG and direct FHG of the CO2 lasers at 77K are presented together with the absolute value of the nonlinear optical constant.
Laser Damage Studies of Silver Gallium Sulfide Single Crystals
Authors: Ruderman Warren , Maffetone John , Zelman David E. , Poirier Derrick M. 
Published: April 2011

AbstractAlthough AgGaS2 single crystals have desirable optical and nonlinear properties, the low laser damage threshold has limited their application for tunable infrared laser sources. Crystals have been studied by ESCA and Auger techniques and the surface of polished crystals has been found to be silver deficient, while the bulk composition is closer to stoichiometry.
Electron-Nuclear Double Resonance Study of the Zinc Vacancy in Zinc GERMANIUM PHOSPHIDE (ZnGeP2)
Authors: Stevens K. T. , Setzler S. D. , Halliburton L. E. , Fernelius N. C. , Schunemann P. G. , Pollak T. M. 
Published: April 2011

AbstractAs-grown crystals of ZnGeP2 are highly compensated and contain significant concentrations of donors and acceptors. The dominant acceptor in ZnGeP2 is believed to be the zinc vacancy. This center is paramagnetic in its normal singly ionized state, and gives rise to an electron paramagnetic resonance (EPR) signal characterized by a resolved primary hyperfine interaction with two equivalent phosphorus nuclei adjacent to the vacancy. The present investigation has focused on electron-nuclear double resonance (ENDOR) measurements of additional hyperfine interactions which are not resolved in the regular EPR spectra. Principal values and principal axes directions for four additional phosphorus nuclei are determined from the ENDOR angular dependence. These parameters support the zinc-vacancy assignment for the acceptor and they provide an experimental check of wave functions generated in future computational modeling efforts.
Frequency Doubling of CW And Pulsed CO2 Lasers Using Diffusionbonded, Quasi-Phase-Matched Gaas Stacks
Authors: Ohmer Melvin C. , Guha Shekhar , Perrin Ronald E. , Rea Laura S. , Yu Phil Won , Fathimulla Ayub 
Published: April 2011

AbstractWe describe the fabrication, characterization and frequency doubling properties of first order stacks of diffusion bonded 2″ diameter GaAs wafers. Near IR imaging through the stacks indicated that excellent bonding was obtained over 40%–70% of the central area of the wafers. A power spectrum analysis of the spectral noise (due to interface reflections) appearing in the transmission data is shown to be a quantitative diagnostic tool useful for determining interface quality and for accurately estimating the thickness of the bonded layers in a stack. The conversion efficiency for a four layer stack at 10.6 microns was found to be 0.03% or 3 mJ for a 10 mJ pulse with a 100 nanosecond pulse length. The corresponding efficiency for cw SHG was found to be 0.0002%.
The Burstein-Moss Shift in Quantum Dots of III-V, II-VI and IV-VI Semiconductors Under Parallel Magnetic Field
Authors: Ghatak Kamakhya P. , Bose P. K. , Majumder Gautam 
Published: April 2011

AbstractIn this paper, we have investigated the Burstein-Moss shift(BMS) in QDs of III-V, II-VI and IV-VI semiconductors in the presence of a parallel magnetic field on the basis of newly formulated carrier disperson laws. It is found, taking QDs of InSb, Cds and CdTe as examples that the BMS increases with increasing doping and decreasing film thickness in ladder like manners. The numerical values of the BMS in QDs are much greater than that of their corresponding values for bulk specimens. The theoretical results as presented here are in agreement with the experimental observations as reported in literature.
CdTe and CdZnTe Room-Temperature X-Ray and Gamma Ray Detectors and Imaging Systems
Authors: Eisen Y. , Shor A. 
Published: April 2011

AbstractCdTe and CdZnTe X-ray and gamma ray detectors in the form of single elements or as monolithic segmented arrays have been shown to be useful in imaging systems utilized in medical, research or industrial applications. These detectors possess inherently better energy resolution than scintillators coupled to either photodiodes or photomultipliers, and they may lead to compact imaging systems or to imaging systems of enhanced spatial resolution and better contrast resolution. Photopeak efficiencies of these detectors is greatly affected by relatively low hole mobility-lifetime product and therefore continuing efforts are still underway to improve the characteristics of both CdTe and CdZnTe materials in order to achieve reproducible detectors with higher photopeak efficiencies for either low or high energy gamma rays.The following paper is divided into three parts: The first part compares the characteristics of planar CdTe and CdZnTe single elements nuclear detectors containing metal contacts. Characteristics include: Charge collection efficiencies for both electrons and holes indicated by the mobility-lifetime product, energy resolutions, leakage currents and robustness in field use. The second part describes excellent spectroscopic results using a lcm thick CdZnTe monolithic segmented pad detector array. This part also compares spectra for various gamma energies obtained by this segmented detector to that of a 1 cm 3 detector acting as a single element planar detector. The third part discusses the characteristics of a new generation nuclear gamma camera for medical diagnostics based on room-temperature CdTe and CdZnTe spectrometers and its advantages over an Anger type scintillating nuclear camera.
Prototype Imaging CD-ZN-TE Array Detector
Authors: Bloser P. F. , Narita T. , Grindlay J. E. , Shah K. 
Published: April 2011

AbstractWe describe initial results of our program to develop and test Cd-Zn-Te (CZT) detectors with a pixellated array readout. Our primary interest is in the development of relatively thick CZT detectors for use in astrophysical coded aperture telescopes with response extending over the energy range ∼ 10 – 600 keV. The coded aperture imaging configuration requires only relatively large area pixels (1–3 mm), whereas the desired high energy response requires detector thicknesses of at least 3–5 mm. We have developed a prototype detector employing a 10 × 10 × 5 mm CZT substrate and 4 × 4 pixel (1.5 mm each) readout with gold metal contacts for the pixels and continuous gold contact for the bias on the opposite detector face. This MSM contact configuration was fabricated by RMD and tested at Harvard for uniformity, efficiency and spatial as well as spectral resolution. We have developed an ASIC readout (IDE-VA-1) and analysis system and report results, including ∼ 4% (FWHM) energy resolution at 60 keV. A prototype design for a full imaging detector array is discussed.
Elementary Analysis Of Line Shapes And Energy Resolution In Semiconductor Radiation Detectors
Authors: Toney J. E. , Schlesinger T. E. , Brunett B. A. , James R. B. 
Published: April 2011

AbstractWe have used an elementary statistical technique to derive a closed-form expression for the hole-tailing line shape produced by photoelectric absorption of monoenergetic radiation in a semiconductor X-ray/γ-ray detector. In the case of compound semiconductors, where the drift length for electrons is much greater than that for holes, the line shape is given by a type of power law, except for a small region very near the photopeak. This analytical result agrees well with Monte Carlo simulations and is used to extract approximate μτ products from a 57Co pulse height spectrum. We also present an expression for the maximum obtainable energy resolution of a semiconductor detector in the presence of leakage current noise and intrinsic statistical fluctuations as a function of material parameters, along with a chart of the optimal band gap as a function of temperature and photon energy. Based on these considerations, the optimal band gap for room-temperature operation is approximately 2.0 eV.
Performance of P-I-N CdZnTe Radiation Detectors and Their Unique Advantages
Authors: Sudharsanan R. , Stenstrom C. C. , Bennett P. , Vakerlis G. D. 
Published: April 2011

AbstractWe present the performance characteristics of CdZnTe radiation detectors with a new P-I-N design and their unique advantages over metal-semiconductor-metal (M-S-M) devices. In M-S-M CdZnTe detectors the bulk resistivity of the substrate largely determines the leakage current. High leakage current is a dominant noise factor for CdZnTe detector arrays, coplanar detectors, and detectors used for low X-ray energy applications. P-I-N devices provide low leakage currents. Early CdZnTe detectors exhibited polarization, were limited to small detection volumes, and some required high deposition temperatures. We have developed a new heterojunction design which can be deposited at low temperatures so that even high-pressure Bridgman CdZnTe can be used. Using the P-I-N design, CdZnTe detectors with high detection volumes (>200 mm3) were fabricated and exhibited low leakage current, good energy resolution, and no polarization. These detectors have significant advantages over M-S-M detectors in three specific areas. First, X-ray fluorescence studies require detectors with low leakage currents to provide less spectral broadening due to electronic noise. Second, less expensive vertical Bridgman CdZnTe material can be used for imaging applications since it normally possesses too low of a bulk resistivity to be useful as a M-S-M detector. Third, leakage currents across the anode grid in large volume coplanar detectors can be significantly reduced
Use of a Monte-Carlo Code to Determine in High Z Semi-Conductor CdTe and CZT, Both Carriers Lifetimes and Mobilities
Authors: Muller E. , Jung M. , Fougfères P. , Hage-Ali M. , Siffert P. 
Published: April 2011

AbstractThis paper deals with a comparison between experimental gamma-ray spectra recorded with CdTe and CdZnTe detectors and a Monte Carlo code simulating the spectrum, in order to extract realistic values of the transport properties of both electrons and holes in these materials. In a second section, these values are compared to that obtained by others using other methods, in order to evaluate the accuracy of the various experimental procedures.
ZnxCd1−xTe Epitaxial Growth by Remote Plasma Enhanced MOCVD Method
Authors: Noda Daiji , Aoki Torn , Nakanishi Yoichiro , Hatanaka Yoshinori 
Published: April 2011

AbstractFor epitaxial growth of compound Zn1−xCd1−XTe by metal organic chemical vapor deposition (MOCVD), it is difficult to obtain a high composition ratio x. In this study, we have adopted a remote plasma enhanced (RPE) MOCVD method for the epitaxial growth. Cd1−xZnxTe with the composition ratio x in the range of 0 to 1 has been obtained while varying the ratio of dimethylcadmium (DMCd) to diethylzinc (DEZn) from 0 to 20%. The crystallinity of the epitaxial films was about 400 to 700 arcsec FWHM defined by X ray diffiraction measurements.
Synchrotron x-Ray Topographic Study Of Dislocations In Gaas Detector Crystals Grown By Vertical Gradient Freeze Technique
Authors: Tuomi T. , Juvonen M. , Rantamäki R. , Hjelt K. , Bavdaz M. , Nenonen S. , Gagliardi M -A. , Mcnally P. J. , Danilewsky A. N. , Prieur E. , Taskinen M. , Tuominen M. 
Published: April 2011

AbstractLarge area transmission and section topographs of semi-insulating gallium arsenide wafers grown by the gradient freeze technique are made with synchrotron radiation at HASYLAB in Hamburg and at ESRF in Grenoble. Several high-resolution images including stereo pairs are obtained on the same film at a time. A typical dislocation line is an arc of a circle which starts from one surface and ends at the same surface. From the disappearance of the dislocation image and using the g · b = 0 criterion it is concluded that the Burgers vector b of the most common dislocations is parallel to 〈110〉. Rather large volumes of the wafer are dislocation-free. Section topographs of epitaxial wafers show defects and strain fields at the interface between an n-type substrate and the epitaxial layers grown by chemical vapor deposition. The results are compared with those obtained from detector performance measurements.
Semi-Insulating InP Particle Detectors For X- And γ-Ray Detection
Authors: Pelfer P. G. , Dubecký F. , Fomari R. , Pikna M. , Krempaský M. , Gombia E. , Darmo J. , Mosca R. , Sekácová M. 
Published: April 2011

AbstractA study of electrical properties and detection performances of the semi-insulating (SI) InP based detectors is presented. Detectors with a top P+ layer and a Schottky back contact give the charge collection efficiency about 90 % and an energy resolution 3.7% (FWHM) for 5.48MeV α-particles at 250 K. Detection of X-rays (122 keV and 60 keV) photons in temperature region 220–250 K is demonstrated. Multiple peaking observed during detection of photons is discussed.
Pl And Epr Spectroscopy Of Point Defects In Detector-Grade Cd1−xZnxTe
Authors: Rablau C. I. , Setzler S. D. , Halliburton L. E. , Doty F. P. , Giles N. C. 
Published: April 2011

AbstractCadmium zinc telluride (CdZnTe) is an emerging material for room-temperature x-ray and gamma ray detectors. The identification and control of point defects and charge compensators are currently important issues. Low-temperature photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies have been used to characterize point defects in CdZnTe crystals grown by the high-pressure Bridgman technique. Luminescence due to shallow donors, shallow acceptors, and deeper acceptors was monitored for a series of samples. An isotropic EPR signal attributed to shallow hydrogenic donors is observed in all samples, and the concentration of shallow donors has been determined. The nature of the defect centers (impurities, vacancies, vacancy-impurity complexes), and the correlation between defect concentration and device performance is discussed.
A Study Of The Composition Uniformity, Electrical And Spectroscopic Properties Of CdZnTe Detectors
Authors: Gagliardi M-A. , Nenonen S. , Gagliardi T. , Hjelt K. T. , Juvonen M. , Tuomi T. , Bavdaz M. 
Published: April 2011

AbstractThe electrical and charge collection properties of a semiconductor detector play an important role in a spectrometer's final performance. However, the studies of these properties often concentrate on only a few samples. In this work over 100 CdZnTe detectors from 12 different growth boules were characterized with one of the following test methods. The composition uniformity was evaluated with low temperature photoluminescence (PL) measurements. From the current-voltage characteristics the differences in CdZnTe detector resistivities were investigated. Charge collection properties, μτ-products, and energy resolutions were characterized with spectroscopic methods using an alpha and isotopic sources. A wide selection of test results are presented indicating the variety of CdZnTe material.
Recent Progress of Electro-optic Polymers for Device Applications
Authors: Jen Alex K-Y. , Yang Qing , Marder Seth R. , Dalton Larry R. , Shu Ching-Fong 
Published: April 2011

AbstractElectro-optic (E-O) polymers have drawn great interest in recent years because of their potential applications in photonics devices such as high speed modulators and switches, optical data storage and information processing1–2. In order to have suitable materials for device fabrication, it is essential to design and develop polymeric material systems (active and passive polymers) with matched refractive indices, large E-O coefficients, good temporal and photochemical stability3–8 The E-O response of an active polymer commonly arises from the electric field induced alignment of its second-order nonlinear optical (NLO) chromophore, either doped as a guest/host system or covalently bonded as a side-chain. Because of the strong interaction among the electric dipoles, the poled structure is in a meta-stable state; the poled NLO chromophores which possess large dipole moment will tend to relax back to the randomly oriented state. As a result, the stability of the poled structure strongly depends on the rigidity of the overall material system. As it might be expected, the continuous increases of the rigidity and Tg of poled polymers imposes constraints on the selection of suitable chromophores that can survive the hightemperature poling and processing conditions. To circumvent this problem, we have developed a series of chromophores that possess conformation-locked geometry and perfluoro-dicyanovinylsubstituted electron-accepting group which demonstrate both good thermal stabilty and nonlinearity. This paper provides a brief review of these highly efficient and thermally stable chromophores and polymers for device applications.