bluuebunny/crossref_metadata_2025_split huggingface dataset:
Er-Related Emission In Impurities (Nitrogen, Oxygen) Implanted Al0.7Ga0.3As
Authors: Uekusa S. , Wakutani M. , Saito M. , Kumagai M. 
Published: April 2011

AbstractErbium (Er) was co-implanted with ( i ) nitrogen (N), ( ii) oxygen (0) and (iii) N and 0 into Al0.7Ga0.3As substrates. Compared with the Al0.7Ga0.3As:Er sample, the 20 K Er3+ -related 1.54 μm integrated photoluminescence (PL) intensity from the Al0 7Ga0.3As:Er,N and Al0.7Ga0.3As:Er,N,O samples were enhanced approximately fifteen and ten times more, respectively. Thermal quenching of Er3+-related emission from Al0.7Ga0.3As:Er,N,O was smaller than that of Er3+-related emission from Al0.7.Ga0.3As-Er,N The 20 K Er3+-related 0.98 μm PL which was radiated by transition from the second excited state (4I1/2) to the ground state (4I1/2) was observed. The 0.98 μm PL intensity from Al0.7Ga0.3As:Er,N,O generally decreased with increasing 0 dosage from 1 × 1013 cm−2 to 1 × 1015 cm−2. These results suggest the formation of different complexes composed of Er and the impurities (N,O). This leads to the generation of complex related traps in the band-gap of Al0.7Ga0.3As as a result of the co-implantation of the impurities. It was found that the trap level of the Er-N complex center lay between 2.05 eV and 1.26 eV, and that of the Er-N-O complex center lay between 1.26 eV and 0.82 eV.
Study of the Homogeneity of Fe-Doped Semiinsulating InP Wafers
Authors: Jimenez J. , Fornar R. , Curti M. , de la Puente E. , Avella M. , Sanz L. F. , Gonzalez M. A. , Alvarez A. 
Published: April 2011

AbstractThe homogeneity of semiinsulating Fe-doped InP wafers is studied using mapping techniques, Scanning Photocurrent (SPC) and Scanning Photoluminescence (SPL). These techniques allow to map with a micrometric spatial resolution the distribution of electrically active levels, in particular substitutional iron levels, Fe2+ and Fe3+. The correlation between both measurements allows to obtain information about the local compensation in terms of the [Fe3++Fe2+]/[Fe2+] ratio. Samples thermally treated were studied in order to analyse the consequences of the annealing on the homogeneity.
γ-Ray Irradiation Effect on the Intersubband Transition in Ingaas/Aigaas Multiple Quantum Wells
Authors: Manasreh M. O. , Chavez J. R. , Kemp W. T. , Hoenshel K. , Missous M. 
Published: April 2011

AbstractIntersubband transitions in n-type InGaAs/AlGaAs multiple quantum wells were studied as a function of 1.0 to 5.0 MRad γ-ray irradiation dose using the optical absorption technique. The spectra were recorded at both 295 and 77K. The results show that the total integrated area of the intersubband transition is decreased as the irradiation dose is increased. This could be explained as follows: The secondary electrons generated from the γ-ray irradiation cause lattice damages where traps and point defects are created. Some of the electrons in the quantum wells are trapped by these defects causing the two dimensional electron gas (2DEG) density to decrease. The reduction of the 2DEG density thus leads to the reduction of the total integrated area of the intersubband transitions.
1.95 μm Compressively Strained Ingaas/Ingaasp Quantum Well DFB Laser With Low Threshold
Authors: Dong Jie , Ubukata Akinoi , Matsumoto Koh 
Published: April 2011

AbstractIn this study, we demonstrate the growth of highly compressively strained InGaAs/JnGaAsP quantum well structures with large well thiclmess by low pressure metalorganic chemical vapor deposition for extending the emission wavelength of lasers. By comparing the photolumineswnce characteristics of quantum wells grown at different temperatures, it is clarified that a relatively high quality quantum well layer emittig at 2.0 μ, can be obtained at a growth temperature of 650°C. 1.95-μm-wavelength InGaAs/InGaAsP highly compressively strained quantum well DFB laser for laser spectroscopy monitors was also fabricated. Double quantum-well DFB laser operating at 1.95 μm exhibits threshold currents as low as 6 mA and 6.2 mW maximum output powers. 2.04-μm-wavelength DFB laser is also described.
Optical Absorption In Hg1−xCdxTe
Authors: Nathan Vaidya 
Published: April 2011

AbstractThe theory of optical absorption due to interband transitions in direct-gap semiconductors is revisited. A new analytical expression for linear absorption coefficient in narrow-gap semiconductors is obtained by including the nonparabolic band structure due to Keldysh and Burstein-Moss shift. Numerical results are obtained for Hg1−xCdxTe for several values of x and temperature, and compared with recent experimental data. The agreement is found to be good.
An imaging CdZnTe detector with coplanar orthogonal anode strips
Authors: Hamel L. A. , Tousignant O. , Couillard M. , Courville J. F. , Jordanov V. T. , Macri J. R. , Larson K. , Mayer M. , McConnell M. L. , Ryan J. M. 
Published: April 2011

AbstractA novel electrode configuration for CZT imaging devices is presented. It is made of focusing, non-collecting anode strips, in one dimension, and collecting anode pixels, interconnected in rows, in the orthogonal dimension. The simulation of such an imaging detector is presented. First, field lines in the detector are computed that show that electrons generated in γ-ray events are collected on the pixels. Charge signals, induced on the pixel and on the strip by drifting electrons, are calculated for several points of interaction inside the detector unit cell. These show that this new detector should retain the spectroscopic and detection efficiency advantages of single carrier (electrons) charge sensing devices such as pixel detectors or spectrometers with controlling electrodes. Furthermore, it retains the main advantage of conventional strip detectors, i.e. an N x N array of imaging pixels realized with only 2N electronic channels. An additional potential advantage is the measurement of the third coordinate, i.e. the depth of interaction in the detector.
Towards Imaging with Polycrystalline Mercuric Iodide Semiconductor Detectors
Authors: Schieber M. , Zuck A. , Braiman M. , Melekhov L. , Nissenbaum J. , Turchetta R. , Dulinski W. , Husson D. , Riester J. L. , Schlesinger T. E. , Toney J. , Sanguinetti S. , Montalti M. , Guzzi M. 
Published: April 2011

AbstractPreparation of polycrystalline mercuric iodide very thin (1 μm) films using laser ablation and thick films (100–600μm), using hot pressing, hot wall vapor deposition and screen printing methods, fabricated as radiation detector plates are briefly described. X-ray diffraction, photoluminescence and optical microscopic measurements as well as response to nuclear radiation will be given. Finally, recent results obtained with a large area imaging pixel detector will be shown.
Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd1−xZnxTe Grown bY High-Pressure Bridgman Method
Authors: Heffelfinger J. R. , Medlin D. L. , James R. B. 
Published: April 2011

AbstractGrain boundaries and twin boundaries in commercial Cd1−xZnxTe, which is prepared by a high-pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer-shaped grain of hexagonal Te (space group P3121). Analysis of a Te precipate by selected-area diffraction revealed the Te to be aligned with the surrounding Cd1−xZnxTe grains. This alignment was found to match the (111) Cd1−xZnxTe planes with the (0111) planes of hexagonal Te. Crystallographic alignments between the Cd1−xZnxTe grains were also observed for a high-angle grain boundary. The structures of the grain boundaries and the Te/C1−xZnxTe interface are discussed.
Amorphous Silicon Sensor Arrays for X-Ray and Document Imaging
Authors: Street R. A. , Apte R. B. , Ready S. E. , Weisfield R. L. , Nylen P. 
Published: April 2011

AbstractLarge area amorphous silicon image sensor arrays are important for x-ray medical imaging and document scanning as well as a variety of other applications where large sensor size is required. The paper first summarizes the present state of the flat panel x-ray imager technology, and compares the two main approaches for x-ray detection. We then describe the performance of a new, large area, high resolution, radiographic imager based on a single amorphous silicon array with 2304×3200 pixels, and an active area of 30×40 cm (12×1 6”).
Radiation Damage in Si Avalanche Photodiodes by 1-Mev Fast Neutrons and 220-Mev Carbon Particles
Authors: Ohyama H. , Hakata T. , Simoen E. , Claeys C. , Takami Y. , Hayama K. , Tokuyama J. , Shigaki K. , Kobayashi K. , Sunaga H. , Miyahara K. , Hososhima M. 
Published: April 2011

AbstractResults are presented of a study on the degradation of the electrical and optical performance of n+p Si avalanche photodiodes, subjected to 1-MeV fast neutrons and to a 220-MeV carbon irradiation. The dark current increases after irradiation, while the photo current decreases. Two dominant hole capture levels, which are responsible for the degradation of performance, are after irradiation observed by DLTS (Deep Level Transient Spectroscopy). The degradation caused by neutron irradiation is smaller than that for carbon irradiation. The differences in the radiation damage are explained by the differences in the number of knock-on atoms and the nonionizing energy loss (NIEL). The recovery behavior of the device performance by isochronal annealing is also reported.
Photoluminescence And The Optimum Growth Conditions Of High Quality ZnS Epitaxial Layers
Authors: Nam Sungun , Rhee Jongkwang , Yu Young-Moon , O Byungsung , Lee Ki-Seon , Choi Y. D. , Yun H. J. , Kim Chang Soo , Jung Yang-June 
Published: April 2011

AbstractHigh quality ZnS epilayers were grown on GaAs and GaP substrates by hot wall epitaxy. The optimum temperature conditions for high quality ZnS epilayer were found. The photoluminescence(PL) spectrum of high quality ZnS epilayers showed sharp and narrow exciton peaks and no self-activated peaks. The room temperature energy gap of ZnS/GaAs was found to be 3.729 eV from the experimentally observed free exciton PL peaks. The temperature dependence of the PL intensity showed a two step quenching process and the temperature dependence of the PL linewidth broadening was tried to analyze in terms of exciton scattering process. From the splitting of the heavy hole and the light hole exciton peaks, the strain was identified.
Optical Studies of the Internal Electric Field Distributions of CdZnTe Detectors Under Bias Conditions
Authors: Yao H. W. , Anderson R. J. , James R. B. , Olsen R. W. 
Published: April 2011

AbstractThe internal electric field distributions of the CdZnTe (CZT) detectors under bias were characterized by optical polarized transmission at a 952 nm illumination utilizing the Pockels electro-optic effect. Two-dimensional (2D) images mapping the internal electrical field intensity changes were obtained to study the performance of CZT room-temperature radiation detectors. Planar and a P-I-N structured CZT detectors were investigated under different operating bias voltages. Analysis of optical profiles from a planar single crystal detector provides a quantitative nondestructive description of the electric field or voltage distributions inside a radiation detector. The P-I-N structured CZT detector showed a nearly uniform electric field in a width which varied with the operating bias voltage. An energyband model of a semiconductor junction with a depletion layer was employed to understand the results.
Reactive Ion Etching (RIE) Induced p- to n-Type Conversion in Extrinsically Doped P-Type hgcdte
Authors: Musca C. A. , Smith E. P. G. , Siliquini J. F. , Dell J. M. , Antoszewski J. , Piotrowski J. , Faraone L. 
Published: April 2011

AbstractMercury annealing of reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type epitaxial layers of HgCdTe (x=0.31) has been used to reconvert n-type conversion sustained during RIE processing. For the RIE processing conditions used (400mT, CH4/H2, 90 W) p- to n-type conversion was observed using laser beam induced current (LBIC) measurements. After a sealed tube mercury anneal at 200°C for 17 hours, LBIC measurements clearly indicated no n-type converted region remained. Subsequent Hall measurements confirmed that the material consisted of a p-type layer, with electrical properties equivalent to that of the initial as-grown wafer (NA-ND=2× 1016 cm−3, μ=350 cm2.V−1.−1).
Direct Measurement of Electron Drift Parameters using Depth Sensing Single Carrier CdZnTe Detectors
Authors: He Z. , Knoll G. F. , Wehe D. K. , Du Y. F. 
Published: April 2011

AbstractThis paper describes some novel techniques developed for directly measuring the electron mobility μe and mean free drift time Te in wide band gap semiconductors. These methods are based on a newly-developed digital data analysis system, in conjunction with single carrier charge sensing and depth sensing techniques. Compared with conventional methods, the new techniques are easier to implement, do not involve curve fitting, allow the use of high energy γ-rays and are not sensitive to variations in pulse rise time.
Polymeric Zinc-Bisquinoline Based Self-Assembled Light Emitting Diodes
Authors: Papadimitrakopoulos F. , Thomsen D. L. , Higginson K. A. 
Published: April 2011

AbstractBifunctional 8,8'-dihydroxy-5,5'-biquinoline (bisquinoline) is reactively self-assembled with diethyl zinc to form a linear coordination polymer. The potential of this method to produce insoluble and intractable structures of controllable supramolecular architecture suitable for semiconducting applications has stimulated an in-depth investigation of the growth mechanism of these polymeric chelates. These films were characterized by FTIR, UV/VIS and photoluminescence spectroscopy. The film growth on glass or indium-tin oxide (ITO) coated substrates was monitored by UV/VIS spectroscopy and ellipsometry. FTIR spectroscopy indicates that the self-assembled films are polymeric in nature. Single layer light emitting diodes exhibited an orange electroluminescence, consistent with the corresponding photoluminescence spectrum
Modulation of the Electronic Properties in Polydithienotiiophene Materials
Authors: Arbizzani C. , Catellani M. , Luzzati S. , Mastragostino M. 
Published: April 2011

AbstractConjugated polymers with narrow band gap are promising candidates for symmetric electrochemical devices, such as electrochromics and redox supercapacitors, which involve the pand n-doped state of the polymer. Polydithienothiophene materials which are prepared from isomer monomers show this characteristic. The copolymerisation of two dithienothiophene isomers leads to materials whose electronic properties depend on the monomer ratio. Optical and electrochemical characterizations of different copolymers are reported and discussed.
Electronic Structure of the Organic Metals κ-Et2cu(SCN)2 and κ-Et2cu[N(Cn)2]Br Measured by Soft X-Ray Emission and Soft X-Ray Absorption
Authors: Stagarescu Cristian B. , Duda L.-C. , Smith Kevin E. , Guo J. H. , Nordgren J. , Haddon R. , Brooks J. S. , Jeromé D. 
Published: April 2011

AbstractThe electronic structure of the two organic, layered metals κ-ET2Cu(SCN)2 and K-ET 2Cu[N(CN)2]Br has been studied using a combination of soft X-ray emission (SXE) and soft X-ray absorption (SXA) spectroscopy. These techniques are powerful probes of the site and angular-momentum resolved partial density of states (PDOS) for both occupied and unoccupied states. Therefore these spectroscopies are particularly suited for an analysis of the density of states of multi-atomic, complex materials as the ET-based organic conductors, allowing site-specific electronic structure to be measured. Furthermore, for certain materials, the electronic structure of specific layers can be measured. We present a preliminary picture of the electronic structure of κ-ET 2Cu(SCN)2 and κ-ET 2Cu[N(CN)2]Br as measured by SXE and SXA performed at the C-Is and N- Is core levels.
Low Pressure Organic Vapor Phase Deposition of Small Molecular Weight Organic Device Structures
Authors: Baldo M. , Kozlov V. G. , Burrows P. E. , Forrest S. R. , Ban V. S. , Koene B. , Thompson M. E. 
Published: April 2011

AbstractA new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) and optically pumped organic lasers. The OLED consisted of a film of aluminum tris- (8 hydroxyquinoline) (Alq3) grown on the surface of a film of N'-diphenyl-N,N'-bis(3- methylphenyl)1–l'biphenyl-4–4'diamine (TPD). Growth on both glass and polyester substrates was accomplished and the resulting heterojunction devices were found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown OLED has an external quantum efficiency of 0.40 ± 0.05% and a turn-on voltage of approximately 6V. The optically pumped organic laser consisted of a film of Alq3 doped with the laser dye, benzoic acid, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3Hxanthen- 9-yl]-ethyl ester, monohydrochloride (Rhodamine 6G). The laser output was centered at approximately 610nm and the lasing threshold was 30μJcm−2. The rapid throughput of LP-OVPD and its use of low vacuum in a horizontal reactor demonstrate its potential to facilitate low cost, roll-to-roll deposition of organic films for many photonic device applications.
Moisture Effect on Polythiophene Electroluminescence
Authors: Weng Tsu-Chien , Jin Bih-Yaw , Ding Ding-Kuo , Sakakibara Mitsuhiko 
Published: April 2011

AbstractThe moisture effect on the neutral and charged thiophene oligomers was investigated using ab initio methods. The influence of water molecules on the geometric relaxation of the neutral and charged tert-thiophenes is found to be important. The torsional distortion in neutral water/tert-thiophene complexes is larger than that of undoped or charged complexes. The relative orientation of the water molecule to thiophene changes dramatically upon the hole injection. The existence of water molecules in the polythiophene suppresses the hole mobility and, therefore, diminishes the efficiency of electroluminescence.
Electron Transfer at the n-InP | Poly(Pyrrole) Interface
Authors: Lonergan Mark C. , Cooney Christopher T. , Myers James A. 
Published: April 2011

AbstractMeasurements of the barrier height by capacitance-voltage techniques and of the equilibrium exchange current density by current-voltage techniques are performed on the rectifying interface between n-InP and poly(pyrrole) (chemically polymerized and characterized by an electrochemical potential of ≈0.2V vs. SCE). The current-voltage data yielded a quality factor of 1.2±0.1 and an equilibrium exchange current density of (1.2±0.6) x 10−9. A cm−2. The capacitance-voltage data yielded a barrier height of 0.73 ± 0.02 V and measured dopant densities within 15% of the expected value. These data, taken together, are inconsistent with thermionic emission theories developed to describe inorganic semiconductor I metal interfaces and often applied to inorganic semiconductor I doped conjugated polymer interfaces. In particular, the ratio of the rate constant for majority carrier electron capture (surface recombination velocity) at the n-InP | poly(pyrrole) interface to that at n-InP | metal interfaces is found to be (6 ± 5) × 10−3.
Nanocomposites of metallophthalocyanines and conjugated Polymers
Authors: Yi Shujian , Jenekhe Samson A. 
Published: April 2011

AbstractNanocomposites of phenoxy-substituted vanadyl phthalocyanine with a t-conjugated polymer, poly(benzimidazobenzophenanthroline ladder), have been prepared from their Lewis acid complexes in organic solvents. The resulting composite thin films obtained by spin-coating have excellent optical transparency and interesting composition-dependent morphology and photoelectronic properties. Enhanced photoconductivity, compared to the components, was observed in some composites with discrete nanoscale metallophthalocyanine aggregates.
Femtosecond Optical Nonlinearity in the Squarylium Dye J-Aggregates
Authors: Furuki M. , Pu L. S. , Sasaki F. , Kobayashi S. , Tani T. 
Published: April 2011

AbstractSquarylium dye with two propyl and two hexyl groups forms a mono-molecular layer with domains of J-aggregates by spreading its chloroform solution at an air-water interface. Fluorescence microscopy and an absorbance evaluation which also considers the reflectance suggest that this Langmuir-film has a close packed two-dimensional structure with a complete Jaggregate formation of all dye molecules. Strong and ultrafast nonlinear optical responses, indicating delocalization of excitons over 30 molecules, have been observed at 5 °C from this ideal mono-molecular layer of J-aggregates.
Doping of Polyaniline by Corona Discharge
Authors: Job Aldo E. , Giacomett JosÉ A. , Mattoso Luiz H. C. 
Published: April 2011

AbstractIt is well known that conductive polyaniline (PANI) films are usually doped by immersing dedoped PANI films in HCI solution. This paper shows that a corona discharge can be successfully employed to dope thin films of polyaniline coated on poly (ethylene terephthalate) films. Similarly to the conventional doping with aqueous HCl the process is accompanied by a color change from blue to green and the conductivity can be tuned in the range from 10−10 up to 0.3 Scm−1. Such new doping method presents several advantages over the conventional one namely, dry process, use of no chemicals, rapidity and no dopant migration. Measurements also showed that the conductivity persists for a long time as observed for films prepared in chemical solution doping. It is believed that this novel technique could be employed in a continuous doping process aiming to produce films with large area for anti electrostatic packing applications.
Dielectric Properties of Sputtered BST on Ir Electrodes
Authors: White B. E. , Chu Peir Y. , Zafar Sufi , Balu V. , Gentile D. , Jones Robert E. , Jiang Bo , Melnick Bradley , Taylor Deborah , Zürcher Peter , Gillespie Sherry 
Published: April 2011

ABSTRACTThe dielectric constant and dispersion of sputtered barium strontium titanate (BST) thin films deposited on Ir electrodes have been measured as a function of frequency and dielectric film thickness. Based on the measured variation in capacitance density with BST film thickness, an interfacial capacitance and thin film capacitance have been extracted. The variation of the interfacial capacitance density and the thin film capacitance density with frequency indicates that the majority of dispersion measured for BST deposited on Ir electrodes is due to the interfacial capacitance, in contrast to results found for Pt electrodes [1]. The temperature dependence of the interfacial capacitance and thin film capacitance has also been measured for these electrodes.