bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dx-Like Centers and Photoconductivity Kinetics in PbTe-Based Alloys
Authors: Akimov B. A. , Bogoyavlenskiy V. A. , Vasil'kov V. N. , Ryabova L. I. 
Published: April 2011

AbstractResults of the study of photoconductivity (PC) kinetics, thermally stimulated currents (TSC) and electrothermal instabilities in PbTe(Ga), Pb1−xMnxTe(In) (0<X<0. 11) single crystals and Pb1-x-ySnxGeyTe(In) (0.06<X<0.2; 0.06<Y<0.12) films are presented. The impurity states in these compounds exhibit a DX-like behavior. Reconstruction of the energy spectrum of solid solutions induced by the composition (X,Y) variation allows us to conclude that the metastable electronic states take par in PC kinetics and accelerate the relaxation process when the metastable levels appear inside the energy gap.
Reduced Al-Ga interdiffusion in GaAs/AlGaAs multiple quantum well structure by introducing low hydrogen content SiNx capping layer for dielectric cap quantum well disordering
Authors: Choi W. J. , Han S. M. , Shah S. I. , Choi S. G. , Woo D. H. , Lee S. , Kim H. J. , Han I. K. , Kim S. H. , Lee J. I. , Kang K. N. , Cho J. 
Published: April 2011

AbstractDielectric cap quantum well disordering (DCQWD) of GaAs/AlGaAs multiple quantum well (MQW) structure was carried out by using SiNx. capping layer grown by plasma enhanced chemical vapor deposition (PECVD). By varying the NH3 flow rate with fixed SiH4 flow rate during the SiNx. growth, the characteristics of the capping film were varied. There was an increase in the energy shift of quantum well photoluminescence (PL) peak after thermal treatment of the samples with rapid thermal annealing (RTA) as the NH3 flow rate was increased, although the thickness of SiNx decreased. This is thought to be due to the increase of hydrogen content in SiNx. film grown at higher NH3 flow rate.
Interdiffusion Mechanisms in GaAs/AlGaAs Quantum Well Heterostructures Induced by SiO2 Capping and Annealing
Authors: Pépin A. , Vieu C. , Schneider M. , Launois H. , Rao E. V. K. 
Published: April 2011

AbstractWe have investigated intermixing enhancement in GaAs/AlGaAs quantum well heterostructures achieved by SiO2 capping obtained by rapid thermal chemical vapor deposition. Evidence of fast Ga pumping inside the SiO2 layer during anneal and simultaneous generation of excess Ga vacancies under the SiO2/GaAs interface is presented. A simple model involving the thermal stress arising from the difference in thermal expansion coefficients between SiO2 and GaAs, is proposed to account for the abnormally fast Ga vacancy diffusion inside the heterostructure. A spatial control of the interdiffused areas can be achieved if a suitable stress field is imposed on the semiconductor surface by the capping layers. We show experimental evidence of this effect using a specific patterning of SiO2/Si3N4 bilayers.
Chemical Bonding on GaAs (001) Surfaces Passivated Using SeS2
Authors: Sun Jingxi , Seo Dong Ju , O'Brien W. L. , Himpsel F. J. , Kuech T. F. 
Published: April 2011

AbstractSelenium disulfide has been demonstrated to be an effective passivant for GaAs (001) surfaces. This chemical treatment can be more robust and effective in reducing surface-states-based Fermi level pinning than other analogous chemical treatments. We have studied SeS2-passivated surfaces, formed by treatment of GaAs in SeS2:CS2 solution, with synchrotron radiation photoemission spectroscopy. The SeS2-treated surface consists of a chemically stratified structure of several atomic layers thickness. The As-based sulfides and selenides appear to reside on the outermost surface with the Ga-based compounds adjacent to the bulk GaAs substrate. The motion of the Fermi level within the band gap was monitored during controlled annealing conditions allowing for the specific chemical moieties responsible for the reduction in surface charge to be identified. As-based species are removed at low annealing conditions with little motion of the Fermi level. GaSe-based species, formed on the surface, are clearly shown to be associated with the unpinning of the Fermi level.
Surface and Interface Properties of InSb Epitaxial Thin Films Grown on Gaas by Low Pressure Metalorganic Chemical Vapor Deposition
Authors: Li K. , Tan K. L. , Pelczynski M. , Fenge Z. C. , Wee A. T. S. , Lin J. Y. , Ferguson I. , Stall R. A. 
Published: April 2011

AbstractThere is increasing interest in the epitaxial growth of high quality InSb thin films on GaAs substrates for many device applications such as infrared optoelectronics. The large lattice mismatch (14.6%) between InSb and GaAs has meant that both growth techniques and conditions have a large influence on the interface properties and consequently the film quality. A surface science study, by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) together with Nomarski microscopy, on the surface and interface properties of InSb/GaAs by metalorganic chemical vapor deposition is presented. It is found fromthe XPS data that the ambient surface is composed of InSb, In2O3, Sb2O3 and Sb2O5. The interdiffusion phenomena are studied by AES depth profiling; the width of interdiffusion region is determined to be 50±10 nm for all the samples grown at different V/III ratios. This is narrower than the data previously obtained for InSb/GaAs interfaces produced by metalorganic magnetron sputtering. The results also demonstrate that uniform and stoichiometric InSb films have been obtained, and that the reproducibility of the MOCVD technique is excellent.
Monolithic 1.55μm Surface Emitting Laser Structure With In0.53Al0.14Ga0.33As/In0.52Al0.48As Distributed Bragg Reflector and Single Cavity Active Layer Grown by Meatalorganic Chemical Vapor Deposition Method
Authors: Baek J.-H. , Lee B. , Han W. S. , Smith J. M. , Jeong B. S. , Lee E.-H. 
Published: April 2011

AbstractVertical cavity surface emitting laser (VCSEL) structure designed at 1.55 μm was grown by low pressure metalorganic chemical vapor deposition method. The VCSEL structure contains top and bottom distributed Bragg reflector (DBR) and single cavity active layer. The DBR was grown with In0.53Al0.14Ga0.33As and In0.52Al0.48As quarter lambda wavelength layer, alternatively. The growth temperature was as high as 750°C to prevent ordering and phase separation of the In0 52Al0.48As layer. The In0.52Al0.48As buffer layer was subsequently grown on the InP buffer layer in order to make an abrupt uniform interface. Unity reflectance was achieved at the center of 1.55 μm with 35.5 pairs undoped DBR layer. The reflectance spectrum of undoped DBR showed a wide flat-band region (greater than 50 nm) where the reflectivity was more than 99.5 %. The center wavelength of DBR was previously determined by an in-situ laser reflectometry technique during the growth of the whole structure. An infrared laser operating at 1.53 μm, which was the design wavelength of DBR layer was used as an in-situ measuring tool. The In0.53Ga0.47As multiple quantum well was used as a cavity layer. The reflectance spectrum of VCSEL structure, which included a single cavity active layer, showed excellent square shaped stop band and also showed an absorption region at the center of the flat band.
High Power Mid-Infrared Interband Cascade Lasers
Authors: Yang B. H. , Zhang D. , Yang Rui. Q. , Lin C.-H. , Murry S. J. , Wu H. , Pei S. S. 
Published: April 2011

AbstractWe have demonstrated 4-μm InAs/InGaSb/AlSb interband cascade lasers with optical output power close to 0.5 W per facet with 1-μs pulses at 1 kHz repetition rate. At 10% duty cycle, an average output power ∼20 mW was realized. External and internal quantum efficiencies exceeding 200% have been achieved at 80 K.
Influence Of Structural Defects And Zinc Composition Variation On The Device Response Of Cdl-xZnxTe Radiation Detectors
Authors: Yoon H. , Scyoc J. M. Van , Gilbert T. S. , Goorsky M. S. , Brunett B. A. , Lund J. C. , Hermon H. , Schiebert M. , James R. B. 
Published: April 2011

AbstractZinc composition variation and gross structural defects including grain and tilt boundaries, twins, and mechanical cracks in high pressure Bridgman Cd1−xZnxTe are characterized and correlated to various detector-related responses. Triple axis x-ray diffraction, double crystal x-ray topography, infrared microscopy, and etch pit density measurements are used to reveal and quantify the spatial distribution and the nature of the structural defects. Mechanical cracks in the material are found to act as conductive ‘shorting paths’, indicated by excessive leakage currents and reduced charge (electron) collection measured along these cracks. Reduced charge collection is also obtained across grain boundaries and in regions with poor crystallinity, indicating that they serve as carrier recombination sites. Finally, the effects of the zinc composition variation on the measured leakage current and the amount of electrons collected are found to be masked by gross structural defects. These characterization techniques provide a wealth of information which can be used not only to study the relationship between the structural and device properties of CdZnTe but also to screen production material for subsequent device fabrication.
Performance of Prototype Segmented CdZnTe Arrays
Authors: Parsons A. , Palmer D. M. , Kurczynski P. , Barbier L. , Barthelmy S. , Bartlett L. , Gehrels N. , Krizmanic J. , Stahle C. M. , Tueller J. , Teegarden B. 
Published: April 2011

AbstractThe Burst and All Sky Imaging Survey (BASIS) is a proposed mission to provide ∼3 arc second locations of approximately 90 Gamma-Ray Bursts (GRBs) per year. The BASIS coded aperture imaging system requires a segmented detector plane able to detect the interaction position of (10 - 150 keV) photons to less than 100 μm. To develop prototype detector arrays with such fine position resolution we have fabricated many 15 mm × 15 mm × 2 mm 100 μm pitch CdZnTe strip detectors. We have assembled these fine pitch CdZnTe strip detectors into prototype 2 × 2 and 6 × 6 element arrays read out by ASIC electronics. The assembly and electronics readout of the 6 × 6 flight prototype array will be discussed, and preliminary data illustrating the uniformity and efficiency of the array will be presented.
Effect Of Thermal Annealing In Bi And Zn Melts On Local Centers In Znse
Authors: Korotkov V. A. , Kovalev L. E. , Bruk L. I. , Gorea O. S. , Ketrush P. I. , Malikova L. V. 
Published: April 2011

AbstractTime-resolved photoluminescence (TRPL) at T=4,2K, electron paramagnetic resonance (EPR) in the range of 4,2K–77K, and wavelength modulated transmittance (WMT) spectra for both undoped and annealed in Bi and Zn melts ZnSe single crystals have been investigated. It is found that the annealing in Bi melts leads to recovery of crystal structure. This supposition is based on the increase of fine and hype fine interaction of residual Mn2+, ions with the simultaneous decrease of the EPR signals line width and the decrease of the F-center line. Furthermore, the band with λmax=520 nm disappears, while exciton band I1 (λmax=445 nm) and edge band Q0 – DAP (λmax=460,2 nm), involving AlZn – LiZn, pairs, become more revealed. At the same time, band narrowing of the TRPL spectra was observed. The annealing in Zn melt causes the increase of the number of F-center. From WMT spectra the energy position of local centers and the dominant influence on impurities and defects of the crystal structure were investigated.
New Applications and Analysis of Avalanche Photodiodes as Detectors for Electrons Ranging from 10 KeV to 300 KeV
Authors: Kodama T. , Osakabe N. , Endo J. , Tonomura A. , Urakami T. , Ohsuka S. , Tsuchiya H. , Tsuchiya Y. 
Published: April 2011

AbstractNew applications of avalanche photodiodes as fast timing detectors for electrons ranging from 10 keV to 300 keV together with an analysis of the response of silicon avalanche photodiodes to the electrons are reported.
A Front End Readout Electronics ASIC Chip for Position Sensitive Solid State Detectors
Authors: Kravis S. D. , Tümer T. O. , Visser G. J. , Maeding D. G. , Yin S. 
Published: April 2011

AbstractA mixed signal Application Specific Integrated Circuit (ASIC) chip for front end readout electronics of position sensitive solid state detectors has been manufactured. It is called RENA (Readout Electronics for Nuclear Applications). This chip can be used for both medical and industrial imaging of x-rays and gamma rays. The RENA chip is a monolithic integrated circuit and has 32 channels with low noise high input impedance charge sensitive amplifiers. It works in pulse counting mode with good energy resolution. It also has a self triggering output which is essential for nuclear applications when the incident radiation arrives at random. Different, externally selectable, operational modes that includes a sparse readout mode is available to increase data throughput. It also has externally selectable shaping (peaking) times.
Study on Deep Level Traps in P-Hgcdte With Dltfs
Authors: Kawata S. , Sugiyama I. , Kajihara N. , Miyamoto Y. 
Published: April 2011

AbstractWe studied the characteristics of deep-level traps in p-type HgCdTe diodes using the Deep Level Transient Fourier Spectroscopy (DLTFS) method. For both holes and electrons, two types of traps were observed. The DLTFS signal intensity of one type of trap increased with the carrier density in the HgCdTe, while the other did not exhibit a monotonic increase. While measuring the stability of these traps during cooling cycles, the DLTFS signal intensity of the first group was almost constant while that of the latter fluctuated with every cooling cycle. Stable traps originated from Hg vacancies, unstable traps are attributed to vacancy-impurity complex defects.
Multifunctional Hyper-Structured Molecules
Authors: Wada T. , Zhang Y. , Aoyama T. , Kubo Y. , Sasabe H. 
Published: April 2011

AbstractTo fill the gap between molecular design and the architecture of three-dimensional functional structures, we propose novel hyper-structured molecules (HSMs) based on welldefined and topologically controlled molecular systems. To this end we have developed carbazole dendrimers, trimers, cyclic oligomers and chromogenic calix[4]arenes as HSMs. Photorefractivity was selected as the primary target function of these HSMs. Oligomers developed in our laboratory exhibit intrinsic photocarrier generation, transport, electro-optic, film-forming and poling properties. These multifunctional properties allow us to demonstrate optical image processing using optical phase conjugation. The topological shapes of indoaniline-derived calix[4]arenes were studied by hyper-Rayleigh scattering. The two indoaniline moieties in calix[4]arene derivatives were pre-aligned so as to enhance the net molecular hyperpolarizability. Besides dendric oligomers, cyclic oligomers can be used as a molecular platform which allows molecular level tuning of shape, size and topology for superior opto-electronic functions.
Synthesis of a New Class of Polyphenylated Phthalocyanines and Metallophthalocyanines
Authors: Walsh Christopher J. , Mandal Braja K. 
Published: April 2011

AbstractWe wish to report the synthesis of a new class of peripherally modified, polyphenylated phthalocyanines (Pcs) and metallophthalocyanines (MPcs). These compounds were synthesized by cyclic tetramerization of functionalized pentaphenylbenzophthalonitriles. The phthalonitriles were made in several steps via Diels-Alder cycloaddition between phenylethynylphthalonitrile and substituted tetracyclones. The polyphenylated design leads to enhanced solubility. Thin films can be cast from solutions of the butoxy and dodecaoxy substituted polyphenylated Pcs and MPcs. Cyclodehydrogenation of the Pcs was studied in an attempt to produce planar systems. Preliminary results indicate the pentaphenyl substituent is too bulky to planarize under the conditions employed.
Optically and Electrically Excited Semiconducting polymer Structures
Authors: Becker H. , Burns S. E. , Denton G. J. , Harrison N. T. , Tessler N. , Wilkinson T. D. , Friend R. H. 
Published: April 2011

AbstractWe report recent advances in the development of conjugated polymer device structures. We have fabricated vertical microcavity structures in which the optical path distance is tunable through control of the orientation of a liquid crystal layer, and demonstrate cavity tuning over 59 nm. We show that this structure allows convenient matching of cavity modes to the freespace emission spectrum from poly(r henylene vinylene), PPV. We have investigated the operation of electrically-excited polymer LEDs with short pulse operation, and have achieved current densities above 103 A/cm2 and peak brightnesses of up to 5 × 106 cd/m 2. We have measured the optical absorption due to the injected carriers under these drive conditions, and find an absorption band near 1.6 eV which we attribute to the presence of polarons. This allows measurement of the injected charge density, from which we deduce that carrier mobilities are strongly enhanced at high fields, reaching values of 4 x 10−2 cm2/Vsec for PPV diodes.
Effect of Morphology on the Electrical Transport Properties of Polyaniline Films for Electronic Applications
Authors: Hardaker S. S. , Eaiprasertsak K. , Yon J. , Gregory R. V. , Tessema G. X. 
Published: April 2011

AbstractAlthough it is well known that the oxidation state of polyaniline is an important characteristic, there are few reports of its influence on the development of morphology and electrical properties in fibers and films. In this work, differential scanning calorimentry is used in conjunction with measurements of temperature dependence of conductivity and thermoelectric power to elucidate the intimate relationship between structure and properties. By increasing the amount of chemical reduction of polyaniline solutions, films are prepared which exhibit a thermal transition between 300 and 385 °C, indicative of melting. Increasing the chemical reduction also increases the conductivity of iodine doped films. The most reduced film exhibited a semiconductor transport mechanism, while the other films could be modeled with a quasi-one dimensional variable range hopping mechanism. The temperature dependence of conductivity also showed increasing order for increasing reduction, consistent with the DSC results.
Molecular Self-Assembly Routes to Optically Functional Thin Films: Electroluminescent Multilayer Structures
Authors: Li W. , Malinsky J. E. , Chou H. , Ma W. , Geng L. , Marks T. J. , Jabbour G. E. , Shaheen S. E. , Kippelen B. , Peyghambarian N. , Andersont J. , Lee P. , Armstrong N. 
Published: April 2011

AbstractThis contribution describes the use of layer-by-layer self-limiting siloxane chemisorption processes to self-assemble structurally regular multilayer organic LED (OLED) devices. Topics discussed include: 1) the synthesis of silyl-functionalized precursor molecules for hole transport layer (HTL), emissive layer (EML), and electron transport layer (ETL) self-assembly, 2) the use of layer-by-layer self-assembly for ITO electrode modification/passivation/hole-electron balancing in a vapor-deposited device, 3) the microstructure/chemical characterization of HTL self-assembly using a prototype triarylamine precursor, 4) fabrication and properties of a hybrid self-assembled + vapor deposited two-layer LED, 4) fabrication and properties of a fully self-assembled two-layer OLED.
Controlling Materials Architecture on the Nanometer-Scale: PPV Nanocomposites Via Polymerizable Lyotropic Liquid Crystals
Authors: Smith Ryan C. , Deng Hai , Fischer Walter M. , Gin Douglas L. 
Published: April 2011

AbstractWe have developed a general strategy for the construction of ordered nanocomposites with hexagonal symmetry, using polymerizable lyotropic (i.e., amphiphilic) liquid crystals. In this approach, self-organizing lyotropic liquid-crystalline monomers are used to form an ordered template matrix in the presence of a reactive hydrophilic solution. Subsequent photopolymerization to lock-in the matrix architecture, followed by initiation of chemistry within the ordered hydrophilic domains to afford solid-state fillers, yields the anisotropic nanocomposites. Composites have been synthesized that have a regular hexagonal arrangement of extended poly(p-phenylenevinylene) (PPV) domains, with a regular interchannel spacing of 4 nm. The photoluminescence of these materials is significantly altered from that of bulk PPV. The dimensions of these nanocomposites can be tuned by varying the size of the hydrophobic tails and/or the nature of the counterion associated with the hydrophilic headgroup of the monomer.
Hexacyanodiazahexadiene (Hcdah) Dianion as a Component of Conducting Complexes
Authors: Yamochi Hideki , Tsutsumi Kiyohiko , Kawasaki Takeshi , Saito Gunzi 
Published: April 2011

AbstractIn the course of the preparation of conductive molecular crystals using ‘percyano anions’, the molecular structure of HCDAH2- was revealed to be a planar geometry having a long diagonal line (≈ 10.4 Å). In (TTF)2(HCDAH)(CH3CN) [block-shaped TTF complex] (triclinic, P1, a = 8.258(5), b = 9.572(6), c= 10.070(4) Å, α = 89.89(5), β = 70.76(4), γ = 80.76(5)°, V = 740.7(7) Å3, Z = 2, final R-value = 0.074), the face-to-face type overlap between the side-byside arranged HCDAH dianions was observed. The donor packing pattern in (BEDOTTF) 6(HCDAH) (monoclinic, P21/a, a = 20.243(3), b = 4.086(1), c = 16.820(4) Å, b = 99.45(1)°, V = 1372.4(5) Å3, Z = 2/3, final R-value = 0.048) was determined to be HCP-type which is the second example in BEDO-TTF complexes.
Thermally Stimulated Luminescence of Naphthylsubstituted Benzidine Derivative and Tris-8-(Hydroxyquinoline) Aluminum With and Without Metal Layers
Authors: Forsythe E. W. , Morton D. C. , Gao Y. 
Published: April 2011

AbstractMultilayer organic light emitting devices based on tris-8-(hydroxyquinoline) aluminum (Alq3) and a naphthyl-substituted benzidine derivative (NPB) have demonstrated practical electroluminescence with a wide range of color. Trap states in these materials play an important role in the carrier transport as well as the light emission process. We report the first observation of thermally stimulated luminescence (TSL) from Alq3 and NPB. The TSL spectra from 8 K to 300 K were used to determine the trap states in Alq3 and NPB. The results for Alq3 show a significant trap distribution at 156 K, which corresponds to a mean trap depth ranging from 0.18 to 0.12 eV, whereas the trap states in NPB are centered from 0.15 eV to 0.01 eV. We have used TSL to study the trap state properties of thin metal layers in the Alq3 films. In addition, we report photoluminescence as a function of temperature for Alq3. TSL spectroscopy provides a technique to study the trap states in a specific layer of the device structure.
Structural Properties of Self-Assembled Poly(zinc-bisquinoline)
Authors: Thomsen D. L. , Phely-Bobin T. , Papadimitrakopoulos F. 
Published: April 2011

AbstractPoly(zinc-bisquinoline) synthesized via a reactive self-assembly technique has been used as an active transport and emitting layer in light emitting diodes. This small molecule self-assembly, pioneered in our laboratory, was shown for the first time to produce pinhole-free films as thin as 400 Å. The ellipsometric trajectory and the refractive index of zinc bisquinoline self-assembled films on silicon were determined using spectroscopic ellipsometry. Psi and Del values were extrapolated at 633nm and 70 deg incidence for films ranging in thicknesses from 0 nm to 125 nm and plotted with model trajectories of 1.65, 1.70, and 1.75 refractive indices. Thin films over 20 nm followed a trajectory having similiar refractive indices between 1.65 and 1.70, indicative of homogenous films. A refractive index of 1.68 ± 0.01 at 633 nm was found to be among the highest reported values for a self-assembled metallorganic multilayer. Atomic force microscopy of a 90 Å film on silicon substrates with mean square roughness of c.a. 12 Å showed an approximate roughness of 14 - 17 Å.