bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fano Factor Determination For CZT
Authors: Redus R. H. , Pantazis J. A. , Huber A. C. , Jordanov V. T. , Butler J. F. , Apotovsky B. 
Published: April 2011

AbstractContinued improvements in the manufacturing of Cd1−xZnxTe (CZT) material have resulted in a practical thermoelectrically cooled X-ray and gamma-ray detector of very high energy resolution. A high resolution spectroscopy system was used to measure the Fano factor in CZT at temperatures down to -40°C. The best resolution of the 5.9 keV 55Fe peak was measured to be 188 eV FWHM, while the best resolution of the 59.5 keV 241Am peak was measured to be 482 eV FWHM. The minimum measured Fano factor was 0.082, with several measurements yielding a value of 0.089±0.005. With a resolution of 4.2 keV FWHM for the 662 keV peak of 137Cs, these detectors demonstrate excellent performance in detecting X-rays and gamma rays.
On the Active Volume of Cadmium Zinc Telluride Gamma-Ray Spectrometers
Authors: Lund J. C. , Brunett B. A. , Viles T. P. , Hilton N. R. , James R. B. 
Published: April 2011

AbstractIn this paper we develop quantitative models to predict the active volume of cadmium zinc telluride (CZT) detectors operated as gamma-ray pulse height spectrometers. Three cases are considered: a conventional planar detector, a unipolar device, and a detector in which electronic signal processing has been applied to correct for charge trapping effects. We find that existing detectors are very limited in their maximum attainable active volume, but unipolar devices with charge correction show promise for producing large active volume devices.
Study of The Homogeneity Of Cadmium Zinc Telluride Detectors
Authors: Hermon H. , Schieber M. , Yang N. , James R. B. , Kolesnikov N. N. P. , Ivanov Yu. N. , Komar V , Goorsky M. S. , Yoon H. , Toney J. , Schlesinger T. E. 
Published: April 2011

AbstractSeveral analytical techniques have been used in the study of the homogeneity of Cadmium Zinc Telluride (CZT) single crystals grown by the vertical high pressure Bridgman (VHPB) method. The presence of black inclusions and tubular hollow pipes has been observed by a few methods, such as photoluminescence (PL), infrared (IR) transmission microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystals investigated were grown commercially in the USA, at the Institute of Single Crystals in Kharkov, Ukraine, and at the Institute of Solid State Physics, Moscow, Russia. We discuss the homogeneity of the various CZT crystals based on the results from these measurement techniques.
Modular 64×64 CdZnTe Arrays With Multiplexer Readout for High-Resolution Nuclear Medicine Imaging
Authors: Woolfenden J. M. , Barber H. B. , Barrett H. H. , Dereniak E. L. , Eskin J. D. , Marks D. G. , Matherson K. J. , Young E. T. , Augustine F. L. 
Published: April 2011

AbstractWe are developing modular arrays of CdZnTe radiation detectors for high-resolution nuclear medicine imaging. Each detector is delineated into a 64×64 array of pixels; the pixel pitch is 380 jim. Each pixel is connected to a corresponding pad on a multiplexer readout circuit. The imaging system is controlled by a personal computer. We obtained images of standard nuclear medicine phantoms in which the spatial resolution of approximately 1.5 mm was limited by the collimator that was used. Significant improvements in spatial resolution should be possible with different collimator designs. These results are promising for high-resolution nuclear medicine imaging.
Fabrication of CdZnTe Strip Detectors for Large Area Arrays
Authors: Stahle C. M. , Shi Z. Q. , Hu K. , Barthelmy S. D. , Snodgrass S. J. , Lehtonen S. J. , Mach K. J. , Barbier L. , Gehrels N. , Krizmanic J. F. , Palmer D. , Parsons A. M. , Shu P. 
Published: April 2011

AbstractA CdZnTe strip detector large area array (∼ 60 cm2 with 36 detectors) with capabilities for high resolution imaging and spectroscopy has been built as a prototype for a space flight gamma ray burst instrument. The detector array also has applications in nuclear medical imaging. Two dimensional orthogonal strip detectors with 100 μm pitch have been fabricated and tested. Details for the array design, fabrication and evaluation of the detectors will be presented.
Lead Iodide X-Ray and Gamma-Ray Spectrometers for Room and High Temperature Operation
Authors: Hermon H. , James R. B. , Lund J. , Cross E. , Antolak A. , Morse D. H. , Medlin D. L. , Soria E. , Scyoc J. Van , Brunett B. , Schieber M. , Schlesinger T. E. , Toney J. , Goorsky M. , Yoon Hojun , Burger A. , Salary L. , Chen K.-T. , Chang Y.-C. , Shah K. 
Published: April 2011

AbstractIn this study we report on the results of the investigation of lead iodide material properties. The effectiveness of a zone refining purification method on the material purity is determined by ICP-MS and ICP-OES and correlated to the electrical and physical material properties. We show that this zone refining method is very efficient in removing impurities from lead iodide, and we also determine the segregation coefficient for some of these impurities. Triple axis x-ray diffraction (TAD) analysis has been used to determine the crystalline perfection of the lead iodide after applying various cutting, etching and fabrication methods. The soft lead iodide crystal was found to be damaged when cleaved by a razor blade, but by using a diamond wheel saw, followed by etching, the crystallinity of the material was much improved, as observed by TAD. Low temperature photoluminescence also indicates an improvement in the material properties of the purified lead iodide. Electrical properties of lead iodide such as carrier mobility, were calculated based on carrier - phonon scattering. The results for the electrical properties were in good agreement with the experimental data.
Dopants in Hgcdte
Authors: Berding M. A. , Sher A. 
Published: April 2011

AbstractIn this paper we discuss our ab initio calculations of native point defect and impurity densities in HgCdTe. Our calculations have explained the experimental finding in general, and in particular have explained the in-active incorporation of the group VII elements under mercury-deficient conditions; have shown that the group I elements have a large fraction of interstitial incorporation, thereby explaining their fast diffusion; and have described a microscopic mechanism for the amphoteric behavior of the group V elements. We discuss the trends found among the compounds in terms of the underlying bond strengths to understand why the various elements behave the way they do.
Metal Contact Formation On Zinc Cadmium Telluride Detector Material
Authors: Burger Arnold , Chen Henry , Chen Kuo-Tong , Shi Detang , Collins W. Eugene , James R. B. 
Published: April 2011

AbstractThe understanding of the electric contact formation process is critical in exploiting the full potential of Cd1−xZnxTe(CZT) material for room temperature detection applications. The metalsemiconductor electrical characteristics were shown in this study to be strongly affected by the surface preparation steps prior to metallization (polishing, and chemical etching), the choice of the metal and contact deposition technique, and by the subsequent surface passivation of CdZnTe. In this paper, we also present the implementation new detector fabrication processing stepsresulting in a significant lowering of the dark leakage current and an improvement in the detector performance.
Characterizing and Circumventing Intermolecular Electrostatic Interactions in Highly Electro-Optic Polymers
Authors: Harper Aaron W. , Zhu Jingsong , He Mingqian , Dalton Larry R. , Garner Sean M. , Steier William H. 
Published: April 2011

AbstractIn general, polymers possessing non-resonant electro-optic activities exceeding 20 pm/V require chromophores with strong electron withdrawing groups (cyanovinyls, carbon acid moieties, etc.) as well as highly polarizable bridges. Although much progress has been made on designing and preparing materials with molecular “electrooptic” activities, their incorporation into polymers to show comparably large bulk electro-optic activities has been met with little success. We report here the mature of the difficulty of the translation of microscopic to macroscopic electro-optic activity. The optimization of molecular activity increases intermolecular electrostatic interactions between chromophores, and these interactions impede induction of polar acentric order in the polymers. Theoretical analysis of the problem is presented, as well as one example of a material that is designed to circumvent these interactions. The resulting material possesses electro-optic coefficients as high as 29 pm/V and optical losses as low as 1.5 dB/cm.
Light-Emitting and Hole-Transporting Polymers for LEDs
Authors: Ohnishi Toshihiro , Doi Shuji , Ueda Masato , Yamaguchi Fumi , Noguchi Takanobu 
Published: April 2011

AbstractVarious copolymers of arylene vinylenes, having strong fluorescence, showed predominantly the emission in the multi-layer device using an electron-transporting material(ETM) such as tris(8-quinolinolato)aluminum(Alq3). The emission from Alq3 was suppressed due to the high hole-injection barrier from the copolymers to ETM in spite of low or no barriers of electron injection from ETM to the copolymers. We have successfully prepared highly hole-transporting polysilane having a triphenylamine group as a side chain(TPA-PS). The hole mobility as high as 10 cm3cm2/Vs is attributable to the intermolecular hopping process facilitated by the interaction between the polysilane backbone and the triphenylamine group. The polysilane is effectively used as a hole transporting material. The bilayer LED device consisting of TPA-PS and Akb3 showed high luminance (2000cd/m2) and high efficiency (4cd/A).
High Mobility and Liquid Phase Processable Organic Semiconductors
Authors: Katz H. E. , Laquindanum J. , Lovinger A. J. 
Published: April 2011

AbstractNew thiophene oligomers and fused ring compounds have been designed and synthesized with the aim of maximizing semiconductor mobility in thin film transistors (TFTs) while allowing for liquid phase processability. Thiophene hexamers with alkyl side chains of various lengths, some with an ether oxygen embedded in the chain, were synthesized, as were derivatives of the novel heterocycle anthradithiophene. Mobilities of the vaporphase-deposited films ranged from 0.01 cm2/Vs for the hexamers to 0.15 cm2/Vs for dihexylanthradithiophene. The latter is the highest mobility yet reported for a polycrystalline film. Cast films of some of these compounds from solution gave mobilities within factors of 2–10 of the corresponding values from gas-phase-deposited films.
Electrical Characterization of Thin Single Crystals of Sexithiophene
Authors: Frisbie C. Daniel , Granstrom Eric L. , Loiacono Michael J. 
Published: April 2011

AbstractExtremely thin, single crystals of sexithiophene (6T), 2–14 nm thick and 2–5 μm in length and width, can be grown an flat gold substrates by thermal evaporation. The thickness dimension corresponds to 1–6 monolayers (ML) of 6T molecules arranged with their long axes nearly perpendicular to the substrate. We have measured the current-voltage (I-V) characteristics through the thickness of these crystallites, after doping them with iodine, using conducting probe atomic force microscopy (CPAFM). The I-V traces are linear in the ±50 mV regime. The conductance (I/V) of the doped 6T crystals does not decrease monotonically with increasing thickness as might be expected, but instead has a maximum at 3 ML thickness, and we discuss several possible explanations for this observation.
Preparation of C60 Charge Transfer Complexes with Organic Donor Molecules and Alkali Doping
Authors: Otsuka A. , Saito G. , Hirate S. , Pac S. , Ishida T. , Zakhidov A. A. , Yakush K. 
Published: April 2011

AbstractSolid charge transfer (CT) complexes of C60 with TSeC1-TTF, EDT-TTF, EOET-TTF, and TDAP (1, 3, 6, 8-tetrakis(dimethylamino)pyrene) were newly prepared. All the obtained black crystals were proved to be neutral despite of their rather strong electron donor ability. Lattice parameters of them except for EOET-TTF complex were determined together with those of HMTTeF·C60, which had been reported with different values. Rubidium doping under a mild condition was examined on the complexes of TDAP, EOET-TTF, HMTTeF, BEDT-TTF, hydroquinone and ferrocene to search for the superconductors of new crystal and electronic structures. Among them, the rubidium-doped ferrocene complex easily showed an apparent superconducting signal in SQUID magnetization measurements. The doping effect on these CT complexes is compared to that on OMTTF complex.
Morphological Effects in the Chemical and Photoluminescent Behavior of Aluminum Tris(8-Hydroxyquinoline) (Alq3)
Authors: Higginson K. A. , Zhang X.-M. , Papadimitrakopoulos F. 
Published: April 2011

AbstractAluminum tris(8-hydroxyquinoline) (Alq3) is presently considered one of the most reliable electron transporting and emitting materials for molecular-based organic light emitting diodes (OLEDs). This paper discusses the effects of sample morphology on the hydrolysis and photoluminescence response of Alq3. The evolution of 8-hydroxyquinoline (8-Hq), a volatile byproduct of the hydrolysis of Alq3, was quantified using gas chromatography/mass spectroscopy (GC/MS) analysis on samples of different morphology. Annealed (more crystalline) samples exhibited greater chemical stability than freshly sublimed films, at the expense of photoluminescence efficiency. These phenomena are discussed with respect to possible failure mechanisms that Alq3-based OLEDs might undergo during prolonged operation.
Light Emitting Devices with Molecularly Doped Polymer Layers. A New Diamine as a Hole Transporting Molecule
Authors: Fattori V. , Cocchi M. , Marco P. Di , Giro G. , Kalinowski J. , Dembech P. , Fabbri G. , Seconi G. 
Published: April 2011

AbstractIn the present contribution a new hole transporting molecule belonging to the triphenyldiamine family (N,N'-diphenyl-N,N'-bis(4-metylphenyl)- 1, 1'-biphenyl-4,4'- diamine) in a polycarbonate matrix is studied as the hole transport layer in a two layer device with Alq3 as emitting layer. The dependence of the electrical and emitting behaviour on the doping level is studied and compared with the vacuum deposited diamine layer also interfaced with Alq3
Injection Efficiency from Various Metals into Trap Free Molecularly Doped Polymers Evaluated from Combined Analysis of Current-Voltage and Time-of-Flight Drift Mobility Data
Authors: Abkowitz M. , Facci J. S. , Rehm J. 
Published: April 2011

AbstractAn experimental procedure which can provide a direct quantitative measure of contact injection efficiency into a trap free transport polymer is described. This technique combines coupled analyses of bias dependent injection current supplied by the contact under test with time-of-flight drift mobility measurements carried out on the same specimen film. This general procedure has been used in a broad range of experiments to evaluate the injection efficiencies from a series of hole injecting contacts of differing work functions into the molecularly doped polymer, TPD/Polycarbonate Two key results are emphasized: (1) Injection efficiency does scale on average with the interfacial barrier, the energy step estimated from substrate workfunction and MDP electrochemical data. In individual cases however, large variations about the norm are clearly identified and can be attributed to variations in the contact surface prior to coating, for example the relative degree of oxidation or, as TOFSIMS reveals, the interdiffusion of metal atoms from adhesive layers which secure the metal coating to a Si wafer substrate. (2) For the case of Au, the injection efficiency of a Au substrate was compared to the behavior of Au vacuum deposited onto the already formed coating under a variety of conditions. The injection efficiency from Au evaporated onto preformed coating initially varies with deposition conditions but relaxes with time under ambient conditions, eventually becoming ohmic. Significant details of this relaxation behavior are described and analyzed in an accompanying paper.
Electrical Properties of Au/Polymer Interfaces
Authors: Ioannidis A. , Facci J. S. , Abkowitz M. 
Published: April 2011

AbstractA trap-free Molecularly Doped hole-transport Polymer (MDP) provides a model system for the study of metal/polymer interfaces by enabling the use of a recently developed technique that supplies a quantitative measure of contact injection efficiency. The technique combines fielddependent injection current measurements from a contact under test with time-of-flighl (TOF) mobility measurements on the same sample. In the present case, MDP films were prepared with two top vapor-deposited contacts, one of Au (test contact) and one of AI (for TOF), and a bottom carbon-loaded polyimide electriode. An unusual phenomenon is investigated whereby injection from Au is initially blocking, evolving to ohmic over time. This contrasts with the behavior expected according to the relative work-functions of Au and of the polymer whereby Au should inject holes efficiently. The samples were aged at various temperatures below the glass transition of the polymer (85°C) and the evolution of current-field measurements and of capacitance is followed in detail over time and analyzed. All Au contacts eventually achieved ohmic injection. Rapid sequence data acquisition enabled the separation of two main processes in the injection evolution. Control measurements ensure that the evolution of the electrical properties is due to the Au/polymer interface behavior and not the bulk. The behavior of Au contacts evaporated under various deposition conditions was compared. Transmission electron microscopy results at the Au/MDP interface were obtained as both a function of time and of deposition conditions. Mechanisms operating at the interface of the evaporated Au films on the polymer are discussed.
Control of the Luminescence Properties in Polythiophenes Solutions by Interring Rotational Disorder
Authors: Luzzati S. , Bongiovanni G. , Catellani M. , Loi M. A. , Milani A. , Mura A. , Piaggi A. 
Published: April 2011

AbstractThe photoluminescence properties of thiophene-based polymers obtained by the random copolymerization of 3,4-dibutylthiophene and 3-butylthiophene are reported. Optical absorption spectra, cw photolumninescence (PL) spectra, PL quantum efficiencies and PL decays have been measured in dilute solutions. By varying the copolymer chemical composition it is possible to tune the intensity and the color of the luminescence spectra in the whole visible range. We evidence the role of disorder, controlled by interring rotations, as the tuning factor for the disexcitation pathway of the photoexcitations in these materials.
Polarized Light-Induced Anisotropy in Polymer Films Doped with Az Dyes in the Photostationary State Studied by IR Spectroscopy
Authors: Tawa K. , Kamada K. , Sakaguchi T. , Ohta K. 
Published: April 2011

AbstractThe anisotropy induced in a series of methacrylate polymers doped with Disperse Orange 3 (DO3, NO2-phenyl-N=N-phenyl-NH2) was investigated by polarized FTIR spectroscopy. Three kinds of methacrylate polymers with different glass transition temperature (Tg), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA), were used as polymer matrices. Observed infrared absorption bands of DO3 in the polymer films were assigned to symmetric (NO2s) and antisymmetric (NO2as) stretching modes of NO2, and the C-N stretching mode of C-NH2 (C-N). The infrared dichroism was observed in these bands under the irradiation. The orientation factors, Kzfn, (f=x, y, z, n=trans, cis), for both isomers of DO3 were determined in the photostationary stite for every polymer matrix. The factors indicate that it is difficult for NO2 group to move in the PMMA during trans-cis-trans isomerization and that it is difficult for NH2 group to move in the PBMA. The dynamical behavior of DO3 molecules which depends on the kind of polymers could be interpreted from orientation factors. This study shows that polarized FTIR spectroscopy is one of the most powerful methods available to analyze the physical mechanisms of photoinduced anisotropy.
Dynamics of Polarons in Guest-Host-System Polymer Light Emitting Devices
Authors: List E.J.W. , Partee J. , Graupner W. , Shinar J. , Leising G. 
Published: April 2011

AbstractThe conjugated ladder-type poly(paraphenylene) is an attractive material for blue polymer light emitting devices (PLED). Blending the active layer with small amounts of a red emitting guest polymer, the emission shifts from blue to red with increasing guest concentration due to efficient excitation energy transfer. The results of photoluminescence detected magnetic resonance, electroluminescence detected magnetic resonance measurements and current detected magnetic resonance measurements on PLEDs based on 0.05w%/o - 2w%/o red emitting poly(perylene-co-diethynylbenzene) (PPDB) in the active layer of the PLED are presented and discussed.
Effects of Sputtered Ir and IrO2 Electrodes on the Properties of PZT Thin Films Deposited By MOCVD
Authors: Shimizu M. , Fujisawa H. , Hyodo S. , Nakashima S. , Niu H. , Okino H. , Shiosaki T. 
Published: April 2011

ABSTRACTThe effect of bottom electrode thickness on the electrical properties of PZT capacitors with Ir and IrO2, electrodes was investigated, with particular attention to switching endurance characteristics. Ir and IrO2 electrodes were prepared by rf magnetron sputtering. PZT films were grown by MOCVD. Secondary ion mass spectrometry (SIMS) analysis showed thick Ir and IrO2 electrodes performed well as a barrier to the PZT elements. On the other hand, strong diffusion at the interface between PZT and the electrodes was observed, when the Ir and IrO2 electrodes were thin. From transmission electron microscope (TEM) observation, it was also found that there was an amorphous intermediate layer at the interface between the PZT and the thick Ir bottom electrode. The switching endurance characteristics were influenced by the thickness of the Ir bottom electrode.
A Study on the Responsivity of Four-Layer Pyroelectric Sensors
Authors: Samoilov Vladimir B. , Kang Seong Jun , Chang Dong Hoon , Yoon Yung Sup 
Published: April 2011

ABSTRACTThe temperature distribution under periodic thermal excitation and the pyroelectric response of a four-layer system consisting of front and back semi-infinite media, a pyroelectric element, and an intermediate layer are found. Numerical results and approximate expressions are obtained for special cases, such as a detector with an air gap between the pyroelectric layer and the bulk substrate and a detector on a substrate of finite thickness an air environment. The responsivities of detectors with a lead-lanthanum-titanate (PLT) sensing element on either a Si and a SiO2 substrate are calculated as functions of the pyroelectric layer and the underlying layer thicknesses. It is found that the detector with an air gap has a frequency-independent responsivity over a wide frequency range. A correlation is found between the type of frequency response in each frequency region and the corresponding dominant mechanism for heat loss.
Reparation and Characterization of BST Thin Films with Hybrid Bottom Electrodes
Authors: Ahn Joon-Hyung , Park Jeong-Ho , Lee Won-Jae , Kim Ho-Gi 
Published: April 2011

ABSTRACTThin platinum layer was used for the modification of the interface state between (Ba,Sr)TiO3 (BST) thin films and RuO2 bottom electrodes. Pt/RuO2 hybrid bottom electrodes were fabricated with various platinum deposition temperatures by a conventional dc magnetron sputtering method. Although the surface morphology and XRD patterns of BST thin films were not changed, the electrical properties of BST films deposited on Pt/RuO2 hybrid electrodes were improved compared to the films on RuO2 electrodes. Dielectric constant (εr) and leakage current density of BST thin films on Pt/RuO2 hybrid electrodes prepared at the platinum deposition temperature of 400°C were 498 and 8.6 × 10−8 A/cm2 at 1.5V, respectively.