bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Four Terminal Poly-Si Tft Suppressing Kink and Improving Reliability
Authors: Park Cheol-Min , Kang Ji-Hoon , Park Kee-Chan , Han Min-Koo 
Published: April 2011

ABSTRACTWe fabricated a new device, which employs counter-doped lateral body terminal (CLBT) in order to suppress kink effects and improve the device stability. Proposed device also employs a buried channel (BC), which increases ON-current and operating frequency. Although LDD structure is not employed in the proposed device, low OFF-current is successfully obtained due to elimination of minority carrier through CLBT. We have measured the dynamic properties of poly-Si TFT device and circuit. The reliability of TFT and circuits after AC stress is also discussed in our paper.The proposed poly-Si TFT has high ON-current and low OFF-current compared with conventional 3-terminal poly-Si TFT. The 4-terminal device characteristics were measured with source and CLBT shorted. The proposed device exhibits superior performance to conventional device in ON-current because BC prevents carrier scattering to gate oxide. We have performed bias and high temperature stress test of ring oscillator in order to investigate dynamic reliability between conventional poly-Si TFT and proposed 4-terminal poly-Si TFT. Our experimental results show that BC enables the device to have high mobility and switching frequency (33MHz at VDD=15V). The minority carrier elimination of CLBT suppresses kink effects and makes superb dynamic reliability of CMOS circuit.
Fabrication of a-Si:H Tfts at 120°C on Flexible Polyimide Substrates
Authors: Sazonov Andrei , Nathan Arokia , Murthy R.V.R. , Chamberlain S.G. 
Published: April 2011

ABSTRACTThe fabrication of large-area thin-film transistor (TFT) arrays on thin flexible plastic substrates requires deposition of thin film layers at relatively low temperatures since the upper working temperature of low-cost plastic films should not exceed ∼200°C. In this paper, we report a fabrication process of a-Si:H TFTs at 120°C on flexible polyimide substrates for large-area imaging applications.Kapton HN (DuPont) films 50 and 125 μm thick and 3 inches in diameter, were used as substrates. Both sides of the polyimide substrate were first covered with 0.5 μm thick a-SiNx. The TFT structure includes: 120 nm thick room-temperature sputtered Al gate, 250 nm thick PECVD deposited a-SiNx for the gate dielectric, 50 nm thick a-Si:H deposited by PECVD from silane-hydrogen gas mixture, 50 nm thick n+ a-Si:H source- and drain contacts, and roomtemperature sputtered Al top contact metallization. We used dry etching for all layers except for the gate and top metal, which were patterned using wet etchants. For purpose of TFT performance comparison, Coming 7059 glass substrates were used.The performance of the fabricated TFT and its improvement with use of optimized a-Si:H and a-SiNx quality will be presented along with a discussion of the intrinsic mechanical stress in the thin film layers will also be discussed.
a-Si TFTs on Thin Steel Foil Substrates: How Thin Can We Go?
Authors: Ma Eugene , Wagner Sigurd 
Published: April 2011

ABSTRACTThe mechanics of thin film-substrate couples indicates that mechanical stress in the active electronic layer can be reduced when films are deposited onto thinner substrates. To explore the question of just how thin a substrate can be, a-Si:H TFTs are fabricated on thin steel foil substrates of various thickness, and performance metrics from devices on each of the substrates are measured and compared.
Electrical Properties of Ultra Thin Tin Oxide Films
Authors: Matsui Yuji , Goto Yoshio 
Published: April 2011

ABSTRACTTin Oxide transparent conductive oxide(TCO) films of less than 20nm in thickness was developed as a substrate for pen touch screens. The films were deposited using APCVD method by hydrolytic decomposition of stannic chloride. Electrical properties and stability to heat treatment were studied in relation to deposition conditions. We found the both properties depends mainly on fluorine concentration in the films. The stability was much improved at reduced fluorine concentration. The film which showed the stability to heat treatment at 600°C heat treatment was attained at the thickness of 20nm.
A Sims Study of Electroluminescent Phosphors: SrS:Cu
Authors: Zhang Lily H. , Wang Larry , Tong Wusheng , Xin YongBao 
Published: April 2011

ABSTRACTThis study has used secondary ion mass spectrometry (SIMS) as a technique for thin film EL material characterization. It has shown that the Cu dopant concentration in the SrS films directly correlates with the luminescent brightness of the EL devices. A series of SrS:Cu, Y were grown using MBE to study the Y co-doping effects. It has been found that Y peak concentration and areal density in the SrS increased as the Y evaporation cell temperature was increased. The maximum PL intensity was found in the sample grown in the middle of the Y cell temperature range used. The Y co-doping has shown to reduce the thermal quenching effects in SrS EL devices. Therefore, in this series of samples, a good correlation has been found between Y and Cu concentration and the EL device performance characteristics.
Temperature and Field Dependence in Polymer Light Emitting Diodes
Authors: Bozano L. D. , Carter S.A. , Scott J.C. , Malliaras G.G. , Brock P.J. 
Published: April 2011

ABSTRACTWe investigate the electrical properties of Polymer Light Emitting Diodes (LED's). The experimental data consists of steady state current-voltage characteristics and radiance as a function of temperature.The basic LED structure is Anode/MEH-PPV (2-methoxy,5-(2'-ethyl-hexyloxy)-l,4-phenylene vinylene)/Cathode, with a polymer film 120-140 nm thick. We use different anode/cathode pairs to study transport and light emission properties. Measurements of external quantum efficiency of bipolar and monopolar devices are presented from 200 K to 300 K. The electron and hole mobilities are derived in the trap-free limit and at high voltages.
Analysis of High-Current Yield of Diamond-Based Field Emitters
Authors: Zhimov Victor V. , Rinne C. Lizzul , Wojak Gregory , Hren John J. 
Published: April 2011

Summary:The maximum emission currents of different diamond coatings were measured and compared quantitatively for the first time. Both the maximum current and the transconductance of field emission tips can be increased significantly by diamond coatings. A strong, nearly linear, dependence of Imax, on thickness was found. The relative effectiveness of CVD diamond, natural diamond, and nanodiamond can be characterized by values of ΔImax/ΔD and ΔVth/D. A quantitative estimate of the thermal conductivity of nanodiamond gave 2.71 W/cm K.
Field Emission from Polymers
Authors: Musa Ismail , Amaratunga G.A.J. , Eccleston W. 
Published: April 2011

ABSTRACTCarbon based materials are considered to be amongst the most promising field emitters for use in displays. Semiconducting polymer (regioregular poly3 octylthiophene) has been found by the authors to have the lowest threshold field reported to date for any carbon based material. The emission process is, we believe, associated with surface irregularities, voids, possibly resulting from solvent evaporation. Field intensification occurs, and as a consequence there is field emission from the top ridges of the voids. The current flowing through these regions is controlled by space charge in traps in the upper half of the energy gap. There is, in addition, current injected from the base of the voids and the two currents mix to give field emission with current IαV1.8 where V is the anode voltage. Measurements on capacitor samples using Aluminium, Gold and Calcium electrodes have been used to examine the conduction processes in the material and these are linked to results of field emission to further illuminate the mechanisms involved and provide a model for the emission process.
Low Phonon Concentration Lasing Glasses for 1.3 μm Amplification
Authors: Mennig M. , Groß F. , Lang I. , Sohling U. , Schmidt H. 
Published: April 2011

ABSTRACTGe-Ga-S-glasses doped with 15000 mole-ppm Pr3+ have been developed for applications in optical amplifiers for 1.3 μm. The formation of crystalline phase separations in Ge 25 Ga10 S65could be suppressed by modification of the glass composition with Sb. Samples have been prepared by melting in sealed silica ampoules at 950°C. Ge-Ga-Sb-S-glasses, doped with 15000 mole ppm Pr3+, were synthesized by addition of Sb2S3up to contents of 14.3 mole% to the composition Ge25,Ga10S65. (corresponding to 83,3GeS2-16,7Ga2S3) or by replacing up to 50 mole% of Ga by Sb. Transparent to opaque glasses were obtained which were free from crystalline phase separations. The modification of the glasses with Sb leads to a remarkable decrease of the transformation temperature of the glasses. However, the temperature working range remains almost unaffected. The transparent glasses exhibit with 15 – 18 μs the same fluorescence lifetimes and the same fluorescence maximum position (1340– 1341 nm) and FWHM (63 μm) as the unmodified Ge-Ga-S-glass. The preparation process for both glass systems could be optimized to obtain monoliths with lengths of several centimeters and intrin- sic optical losses of only 0.05 dB/cm at 1.3 μm (after correction of reflection), which is of very high importance for the future development of planar amplifiers with remarkable net gain.
High Resolution Time and Frequency Resolved Spectroscopy for the Study of Photophysical Processes in Luminescent Materials
Authors: Farris Bruce , Smith Anthony , Martoglio Richard , Spangler Lee H. 
Published: April 2011

ABSTRACTA method for obtaining time and frequency resolved spectra with high spectral and temporal resolution over a broad spectral range is presented. Step – scan Fourier transform spectroscopy permits spectral coverage from UV to mid IR with sub nanosecond resolution making it possible to track emission from multiple manifolds with full temporal resolution in a single experiment. Data for several rare-earth doped crystalline materials exhibiting multiple emission bands and including evidence of energy transfer is shown.
An Investigation of the Chromaticity of Blue Emitting Yttrium Silicate
Authors: Bosze E. J. , Hirata G. A. , Mckittrick J. 
Published: April 2011

ABSTRACTThis investigation studied the effects of Ho3+ and Er3+ on the luminescence of the blue emitting phosphor yttrium silicate, (Y1-mCem)2SiO5. Yttrium silicate has a large emission tail that extends into the red portion of the visual spectrum. To improve the chromaticity of this phosphor to give it a more saturated blue color, the emission intensity of the tail needs to be decreased. Photoluminscence and low-voltage cathodoluminescence measurements were performed on yttrium silicate phosphors with varying concentrations of Gd3+, Ho3+ and Er3+. It was found that when co-doping with Ho3+ and Er3+, the relative intensity of the emission tail was decreased, but so to was the overall luminescence intensity of this phosphor.
Application of Photoacoustic Spectroscopy to Porous Silicon
Authors: Ohmukai Masato , Kobayashi Akiharu , Uehara Nobutomo , Yamazaki Tetsuya , Fujihara Shinji , Tsutsumi Yasuo 
Published: April 2011

ABSTRACTWe are investigating applicability of photoacoustic (PA) spectroscopy to porous silicon. Since PA spectroscopy is based on a non-radiative relaxation process, the measurement is of importance as a counterpart to photoluminescent spectroscopy. We studied a dependence of a PA amplitude on a chopping frequency and discussed the influence of a PA signal originated in a silicon substrate. The frequency dependence was elucidated with a two-layer model. Differences in PA spectra are correlated with a photoluminescent efficiency. From the correlation, we believe that non-radiative centers quench the efficiency.
Effects of Gas Environments on Porous Silicon Photoluminescence
Authors: Francia G. Di , Ferrara V. La , Lancellotti L. , Quercia L. , Fasolino T. 
Published: April 2011

ABSTRACTThe photoluminescence response of a series of porous silicon samples, obtained by electrochemical etching of n-type CZ-silicon, has been recorded in various gas environments. A quenching is reported when porous silicon is in the presence of an oxidising ambient (dry air or acetone vapours in dry air). Process reversibility depends on the duration of laser illumination. Quenching is also recorded if porous silicon is in the presence of acetone vapours in nitrogen ambient, where complete reversibility is however shown. Moreover, the peak wavelength is red shifted in dry air and blue shifted in acetone vapours. Irreversible quenching is related to the growth of a thin oxide layer on the emitting nanostrucures.
Strong Activator-Host Interaction in Rare Earth Borate Phosphors
Authors: Mordkovich V.Z. , Umnov A.G. , Inoshita T. 
Published: April 2011

ABSTRACTCe3+ luminescence in yttrium cerium aluminium borates was studied. A substantial red shift in photoluminescence and low-voltage cathodoluminescence spectra was found to be induced by Ce concentration increase. Complicated concentration dependence of emission intensity and strong influence of cerium content on emission wavelength suggest strong activator-host interaction in rare earth borates.
Color Engineering of Garnet Based Phosphors for Luminescence Conversion Light Emitting Diodes (Lucoleds)
Authors: Batentschuk M. , Schmitt B. , Schneider J. , Winnacker A. 
Published: April 2011

ABSTRACTFor white light generation with LUCOLEDs the phosphors on the base of YAG:Ce are ideally suited. The variation of the phosphor composition were performed. Powder Ga-substituted phosphors as well as Lu,Y,La,Sc- substituted epitaxial films were investigated. The effects on luminescence and excitation spectra, which is relevant for luminescence conversion, are reported.
Energy Transfer in Erbium-Doped Silicon Nanoclusters: A Comparison of Silicon-Rich Silica and Silicon Nanopowders
Authors: Kenyon A.J. , Botti S. , Chryssou C.E. , Trwoga P.F. , Pitt C.W. 
Published: April 2011

ABSTRACTA number of groups have demonstrated an efficient excitation transfer mechanism in erbium-doped crystalline and porous silicon. It has been postulated that this is a carrier-mediated transfer, which points to the possibility of fabricating efficient silicon-based 1.5 µm emitters.We have previously reported the existence of a similar transfer mechanism in silicon-rich silica. In this paper we extend this study to include silicon nanopowders and demonstrate the existence of the same mechanism. Comparing the photoluminescence excitation spectra of erbium doped silica, silicon-rich silica and silicon nanopowders we show that the coupling mechanism enables broad-band pumping of the rare-earth ion.We have also measured carrier lifetimes in the nanoclustered silicon materials using photoinduced free carrier decay. The measured lifetimes are surprisingly long (in the 2-10 millisecond regime), and we discuss the effect of this on the transfer mechanism.
Optimization of Mixed Storage Phosphors of the Type (Ba,Sr)F1+xBr1−x:Eu for Digital X-Ray Radiography
Authors: Batentschuk M. , Hackenschmied P. , Winnacker A. , Moll M. , Fasbender R. 
Published: April 2011

ABSTRACTThe possibility of further improving the sensitivity of the widely used BaFBr:Eu X-ray storage phosphor is investigated. The influence of CsF- and EuF3-doping on the stimulation spectrum is identical to the one of other ways to vary F/Br-ratio of this mixed crystal. The effect of CsF-doping turns out to be not primarily due to a replacement of Ba2+ by Cs1+ and subsequent charge comensation, but rather to the change in the F/Br ratio. Sr doping not only gives rise to FA(Br; Sr2+)-center formation but, at the same time increases the PSL-response in the bands ascribed to F(Br -)-centers.
Film Preparation Conditions and Characterization of Co-Deposited Tungsten Doped Zinc Oxide Phosphor
Authors: Sobti Jasleen Bombra , Bhatia V. , Babuchna P. M. , Weichold Mark H. 
Published: April 2011

ABSTRACTNeed for efficient blue light emitting source for optoelectronic device applications such as flat panel displays has made the research in luminescent material ever so important. Tungsten doped zinc oxide (ZnO:W) has been identified as a blue light emitting phosphor exhibiting cathodoluminescence near 490 tim. This paper details work done on ZnO:W phosphor preparation conditions for efficient light emission from the phosphor. Material characterization to identify the possible source of blue light emission will also be discussed.
Preparation and Luminescence of Europium Doped Zinc Silicate Phosphor
Authors: Zhang H. X. , Zhou Y. , Kam C. H. , Lam Y. L. , Chan Y. C. 
Published: April 2011

ABSTRACTEuropium doped zinc silicate (Eu:Zn2SiO4) phosphors in the forms of nanoscale powder and film has been prepared by sol-gel method. XRD analysis indicz: ed that the powders have willemite structure with a small amount of triclinic structure and the filn has, pure willemite structure. Photoluminescence measurement showed that strong red emission of Eu3+5D0→7 F2transition could be obtained under excitation at both 256 and 393 nm. Luminescence decay of the emission under 393 nm excitation can be fitted by a single exponential, yielding a decay time τ =1.43 ms; and the luminescence under 256 nm excitation shows double exponential decay with a slow decay time τs,=2.13 ms and a fast decay time τf =2.05 ms.
Time-Resolved Transport of Electrons and Holes in Conjugated Polymers
Authors: Pinner D. , Friend R. H. , Tessler N. 
Published: April 2011

ABSTRACTDetailed experimental and theoretical analysis of the pulsed excitation of polymer light emitting diodes is presented. We find a set of universal transient features for different device configurations which can be reproduced using our phenomenological numerical model. We find that the temporal evolution of the electroluminescence can be characterised by five main features: i) a delay followed by; ii) fast initial rise at turn-on followed by; iii) a slow rise (slower by at least one order of magnitude); iv) fast modulation (<15ns, unresolved) at turn-off followed by v) a long-lived exponential tail. We suggest a method for extracting mobility values which is found to be compatible with CW drive schemes. Mobilities for holes and electrons are extracted for a poly(p-phenylenevinylene) co-polymer and poly(di-octyl fluorene).
Photovoltage in Conjugated Polymer Photovoltaics with a Titanium Dioxide Anode
Authors: Arango A. C. , Brock P. J. , Carter S. A. 
Published: April 2011

ABSTRACTWe study the photovoltaic response of inorganic/organic composite devices containing the conjugated polymer, MEH-PPV, and a semi-transparent layer of titanium dioxide (TiO2) nanoparticles, which is similar to that employed in the Grätzel photoelectrochemical cell. Comparison of the photovoltage obtainable under illumination with either a Au, Ag, Al or Ca back electrode suggests that the built in potential is determined largely by the difference between the quasi Fermi level of the TiO2 under illumination and the work function of the back electrode. A qualitative model for charge generation and transport through the device is presented.
Improving the Crystallization Resistance of Aluminum(III) 8-Hydroxyquinoline-Based Emitting Materials by Entropic Stabilization
Authors: Higginson Keith A. , Yang Baocheng , Papadimitrakopoulos Fotios 
Published: April 2011

ABSTRACTThe morphological stability of evaporated films of aluminum(III) 8-hydroxyquinoline (Alq3) was investigated. Films which were found to be non-crystalline by x-ray diffraction upon deposition, crystallized rapidly upon annealing, especially where defects were present. Blends of Alq3with aluminum(III) 5-methyl-8-hydroxyquinoline were proposed for thermally stable amorphous emitting layers in light-emitting diodes. Films coevaporated at a 1:1 ratio did not show evidence of crystallization or phase separation even after long annealing periods at temperatures as high as 160°C.
Conjugated Poly-P-Phenylene (PPP) From Poly(1,3-Cyclohexadiene) (PCHD) Homo- and Block Copolymers: Controlled Processability and Properties
Authors: Mays J. , Hong K. , Wang Y. , Advincula R.C. 
Published: April 2011

ABSTRACTConjugated polymers have been used as solid-state materials for a variety of opto-electronic applications. Thus, their processability in a number of device fabrication protocols is an important consideration. In this report, we indicate our results on the synthesis of conjugated poly-p-phenylene (PPP) materials derived from poly(1,3-cyclohexadiene) (PCHD). The precursor PCHD polymers were synthesized by living anionic polymerization to produce homo-and block copolymer configurations with polystyrene. We have used a variety of initiators, solvent, and temperature conditions to determine the right parameters for obtaining narrow MWD polymers. The conditions for polymerization determined the ratio of 1,2 and 1,4 isomers in the microstructure. We then proceeded with conversion to PPP derivatives using a dehydrogenation reaction with chloranil. Our results indicate a systematic conversion to a conjugated polymer with increased solubility and photoluminescence properties. The microstructure, MW and block copolymer composition affecting the processability and conversion properties dramatically.
Bridged Polysilsesquioxanes with Improved Second Order Nonlinear Optical Properties and Stability
Authors: Hobson S. T. , Zieba J. , Prasad P. N. , Shea K. J. 
Published: April 2011

ABSTRACTWe report the synthesis and sol-gel polymerization of 4-nitro-N,N-bis[(3- triethoxysilyl)propyl]aniline 1. An efficient synthesis of the monomer was developed by the hydrosilylation of N, N-diallyl-4-nitroaniline. Optical quality thin films were synthesized by spin coating an n-butanol solution of 1 using formic acid as catalyst and source of water. We improved the temporal stability of the NLO signal from films prepared from 4-nitro-N,N-bis[(3-triethoxysilyl)propyl]aniline by increasing the intensity of the poling field and extending the heating period during the poling/curing stage. By Maker fringe analysis, a X(2) value of 9 × 10−8 esu was measured for these polysilsesquioxanes. If one assumes that the major component of the NLO effect is along the z-axis, the X(2) value corresponds to a d33 coefficient of 18.9 pm/V and a r33 value of 4.7 pm/V.
Electrical Field Effects on Crystalline Perfection of MBA-NP Crystals by Mapping of Bragg-Surface Diffraction
Authors: Morelhão S.L. , Avanci L.H. , Hayashi M.A. , Cardoso L.P. 
Published: April 2011

ABSTRACTThe interaction of weak electrical field with the molecular dipole of the MBA-NP crystals is investigated. Such interaction affects the misorientation and size of the perfect diffracting regions of the crystal, which is monitored by mapping the Bragg-surface diffraction condition. This diffraction technique has also confirmed that the diffracting regions are large enough to allow primary extinction and the non-uniform mosaicity along the crystal surface.
Synthesis and Characterization of Some New Metal-Containing Polymers for Third Order Nonlinear Optical Applications
Authors: Bader Mamoun M. , Pham Phuong-Truc T. , Molli Angela , Moser Justin , Meyres Kevin , Albright Leslie 
Published: April 2011

ABSTRACTWe report here our preliminary results on the synthesis and characterization of a new family of metal-containing polymers incorporating 8-hydroxyquinoline. These polymers have the following structural features: a metal center, a chromophore, and a flexible spacer group with variable length. These structural features allow us to have an appreciable degree of control over various physical properties of these materials. We report on three different types of polymers: polyethers, polyesters, and polyamides. The chromophores in these polymers were incorporated in the backbone and in one case as a side chain of polyesters.