bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single Molecule Studies of a 2,7-Bis-(Phenylethenyl)fluorenone: Implications for Green-Emission Bands in Fluorene-Based OLEDs
Authors: Odoi Michael Y , Hammer Nathan I , Rathnayake Hemali , Lahti Paul M , Barnes Michael D 
Published: April 2011

ABSTRACTThe color purity of blue polyfluorene fluorescence emission is often adversely contaminated by green emission bands. The origin of this green emission has been attributed to various factors including on-chain oxidation of fluorene leading to monomeric fluorenone emission and inter/intra-chain interaction between segments of fluorenone units leading to excimer formation on the polyfluorene backbone. We report here emission properties at the bulk and single molecule level of a molecular fluorene derivative and compare them to those of its oxidative fluorenone derivative. Whereas the bulk fluorescence emission of 2,7-bis(3,4,5-trimethoxyphenylethenyl)-9,9-diethyl-9H-fluorene (OFPV) exhibits a blue to blue-green emission at about 480 nm, 2,7-bis(3,4,5-trimethoxyphenylethenyl)-9,9-diethyl-9H-fluorenone (OFOPV) shows red luminescence with a peak centered at about 630 nm. However, the peak position for OFOPV shifts to higher energies (∼540 nm) upon dilution or dispersion in polymer matrices like PMMA or Zeonex. Single molecule measurements of OFOPV show fluorescence spectra dominated by peaks around 540 nm, with a small minority at longer wavelengths that are attributed to emission from dimers or higher aggregates. This distribution indicates that monomeric emission of OFOPV is green, consistent with green emission bands seen in polyfluorenes.
Photoluminescence and Electroluminescence in Combination of Rare-Earth Metal Complexes and Phosphorescent Molecules
Authors: Kin Zenken , Hino Yuichi , Kajii Hirotake , Hasegawa Yasuchika , Kawai Tsuyoshi , Ohmori Yutaka 
Published: April 2011

ABSTRACTWe investigated luminescent properties of rare-earth metal complexes and phosphor-rescent molecules doped in a conducting polymer. Electroluminescent (EL) properties in combination of red emissive europium complex of tris(di-benzoylmethane)-mono(4,7-diphenyl-phenanthroline) europium (III) (Eu(dbm)3phen) and blue phosphorescent molecule of bis[(4,6-difluoro-phenyl)-pyridinato-N,C2'] (picolinate) iridium (III) (FIrpic) doped in poly(N-vinyl-carbazole) (PVK) and a new rare-earth complex tris(hexafluoroacethylacetonato) (phenan-throline) samarium(III) [Sm(hfa)3(phen)2] have been investigated as an EL emitter. White EL has been obtained from mixed layer of Eu(dbm)3phen and FIrpic, and EL from Sm complex has been obtained. Energy transfer and the emission mechanisms have been discussed.
Improvement of Short Channel Mobility and Operational Stability of Pentacene Bottom-Contact Transistors with a Sulfuric Acid and Hydrogen Peroxide Mixture (SPM) Treatment of Au Electrodes
Authors: Kawakami Haruo , Maeda Takahiko , Kato Hisato 
Published: April 2011

ABSTRACTWe report a reduction in the contact resistance between pentacene and Au source/drain electrodes of organic field effect transistors (OFETs) with bottom-contact structure. By immersing the Au electrodes in a sulfuric acid and hydrogen peroxide mixture (SPM), the injection barrier between the Au electrodes and pentacene was lowered by approximately 0.2 eV and the contact resistance significantly decreased. The fabricated bottom-contact OFETs revealed a field-effect mobility of more than 0.66 cm2/Vs at a channel length ranging from 3 to 30 μm, which is comparable to that of top-contact OFETs with a 50 μm channel length. The transfer characteristics of the OFET with the SPM treatment were stable even after 44days storage in air under room illumination without any passivation. Moreover, the drain current reduction due to threshold voltage (Vth) shift under continuous application of gate voltage quickly recovered toward the original value with unloading of gate voltage.
Structure and Morphology of Tetracene Thin Films on Hydrogen-Terminated Si(001)
Authors: Qin X. R. , Tersigni A. , Shi J. , Jiang D. T. 
Published: April 2011

ABSTRACTScanning tunneling microscopy (STM), atomic force microscopy (AFM) and near-edge x-ray absorption fine structure (NEXAFS) have been used to study the structure of tetracene films on hydrogen-passivated Si(001). A distinct growth morphology change that occurs around a few monolayers of film thickness was characterized. This coverage-dependent film structural phase transition leads to a molecularly ordered film structure commensurate with the crystalline substrate.
Effects of Environment on Modlus of Low-k Porous Films Used in Back End of Line
Authors: Simonyi Eva E , Dimitrakopoulos Christos D , Lane Michael , Liniger Eric , Volksen Willi 
Published: April 2011

ABSTRACTReliability is an important requirement for the newly developed porous low-k ILD materials that are being introduced into (BEOL). Dependence of Young's moduli, as measured by nanoindentation technique, on the environment [such as high relative humidity, water immersion and recovery] is presented along with FT-IR spectra for a number of films with different k values. Effect of the moduli changes on cracking behavior is also discussed.
Dielectrophoresis-Based Assembly and High-Frequency Characterization of Carbon Nanotube Bundles
Authors: Woodson Michael , Tselev Alexander , Liu Jie 
Published: April 2011

ABSTRACTAs the size of integrated circuit elements decreases, the properties of carbon nanotubes (CNTs) become increasingly attractive for interconnect applications. To be used by industry, full characterization of the electronic properties of CNT aggregates is essential.Dielectrophoresis from CNTs suspended in liquid has been demonstrated as a simple route to bundles of aligned parallel nanotubes. We describe a method by which circuits including such bundles may be fabricated, and provide some high-frequency measurements of their electrical properties. The contributions of the contacts can be separated from those of the bundle itself.
Porosity and its Effect on Barrier Performance of Thin Electroless Cobalt Alloy Caps
Authors: Chen Qingyun , Liu Jun , Walker Elizabeth , Hurtubise Richard , Stritch Daniel , Lin Xuan 
Published: April 2011

ABSTRACTPinhole densities of electroless cobalt alloy films on copper substrate are characterized using optical and electrochemical methods. The impact of pits or pinholes on deposit film barrier property is discussed. The improved film barrier property is shown by reduction of pits formation through deposition process optimization.
Copper Chemical Vapor Deposition using a Novel Cu(II) Precursor for Contact Via Filling Process
Authors: Zama Hideaki , Nishimura Yuuji , Yago Michiyo , Watanabe Mikio 
Published: April 2011

ABSTRACTChemical vapor deposition (CVD) of copper using both a novel Cu(II) β-diketonate source and hydrogen reduction process was studied to fill contact vias with the smallest diameter in the 32nm and more advanced generation chip. Pure Cu films were grown under the condition with the product of hydrogen partial pressure and H2/Cu source molar ratio being over 1,000,000. We succeeded in filling the 40-nm-diameter contact vias by optimizing the growth condition of the Cu-CVD in both substrate temperatures and reaction pressures.
A Trial for Micro-Scale Evaluation of Adhesion Strength around Cu Metallization Systems
Authors: Kamiya Shoji , Arakawa Hitoshi , Shimomura Hiroshi , Omiya Masaki 
Published: April 2011

ABSTRACTAdhesion strength of the interface between Cu film and SiCN cap layer for IC metallization system was evaluated by a technique developed by the authors. In this technique, microscopic specimens with the in-plane dimension less than 10 μm were fabricated by focused ion beam system and loaded directly by a sharp diamond stylus with submicron tip radius. By comparing the crack extension behavior with the three-dimensional numerical simulation, the interface adhesion energy was evaluated to be 5 J/m2. The same interface was subjected also to the four-point bending experiment, which is widely applied to interface adhesion measurement. The evaluation results by the two techniques agreed reasonably well with each other.
Silicon Nanocluster Formation by a Pulse-type Gas Feeding Technique in the LPCVD System for the Nonvolatile Memory Applications
Authors: Kim Kyoungmin , Kim Eunkyeom , Bae Myeongwook , Son Daeho , Lee Juhyung , Han Moonsup , Sok Junghyun , Park Kyoungwan 
Published: April 2011

AbstractWe developed a pulse-type gas-feeding technique in low pressure chemical vapor deposition system in order to grow Si nanoclusters with high density and uniform size. The maximum density and average size of the Si nanoclusters were 7 × 1011/cm2 and 7 nm, respectively. Floating gate memory devices containing the storage node of the Si nanoclusters were fabricated. The memory window was 4.5 V when the writing and erasing voltages were +14 V and −18 V, respectively. The writing and erasing times were measured to be 1 ms and 200 ms, respectively. The retention time of Si nanocluster nonvolatile memory was estimated about 10 years.
Deposition Of Uniform Size Metallic Nanoparticles For Use In Non Volatile Memories
Authors: Verrelli Emanuele , Tsoukalas Dimitris , Giannakopoulos Konstantinos , Ioannou Dimitris 
Published: April 2011

AbstractIn this work we investigate the non-volatile memory behavior of Ni nanoparticles embedded within an insulating matrix. Nickel nanoparticles are deposited at room temperature by a new high-vacuum technique over a 4 nm tunneling thermal SiO2 layer followed by the deposition of HfO2 as a control insulator. Memory windows of ∼1.5V are observed in MOS capacitors at gate pulse voltages of 8V. Charge retention for write and erase state clearly indicate long time charge storage behavior.
A Comparison of N+ type and P+ type Polysilicon Gate in High Speed Non-Volatile Memories
Authors: Kim Moon Kyung , Chae SooDoo , Kim Chung Woo , Lee Jo-won , Tiwari Sandip 
Published: April 2011

AbstractThe polarity of gates and the threshold voltages are primary parameters that determine the electric fields in the gate stack region of non-volatile memories. This field is central to programming, retention and the other characteristics of the devices. We have investigated the effect of the gate polysilicon polarity, experimentally, for silicon-oxide-nitride-oxide-silicon (SONOS) memory devices on silicon-on-insulator (SOI) wafers. An ultra-thin oxide-nitride-oxide (ONO) film with high trap density and strong localization of the trapping provides the scalability and retention in our structures. The effect of ONO film, grown and deposited and of doping was simulated and characterized. Retention is affected by the electric field between the control gate and the storage node. Our experiments and simulations verify the consequences of different polarity of control gates through the change in electric field that they cause in retention and erase times for n+ and p+ polysilicon gate SONOS memories is verified through the characteristic energies of the processes.
Nonvolatile Resistive Switching Devices Based on Nanoscale Metal/Amorphous Silicon/Crystalline Silicon Junctions
Authors: Jo Sung Hyun , Lu Wei 
Published: April 2011

AbstractM/a-Si:H/c-Si based nonvolatile resistive switching devices with active areas down to 50 nm×50 nm have been fabricated and explored. Close to 100% device yield was achieved without necessity of high voltage forming process. Both rectifying switching and non-rectifying switching were demonstrated in a controllable fashion. The potential for this structure as nanoscale nonvolatile memory devices was investigated in terms of scalability, retention time, endurance and switching speed. The device showed switching speed faster than 5 ns, endurance cycles more than 106 and retention time longer than 150 days without any degradation of stored data. The devices exhibit improved resistance switching ratio when scaled down.
Reversible Multi-level Resistance Switching of Ag-La0.7Ca0.3MnO3-Pt Heterostructures
Authors: Shang Dashan , Chen Lidong , Wang Qun , Wu Zihua , Zhang Wenqing , Li Xiaomin 
Published: April 2011

AbstractResistance random access memory (RRAM) has attracted intense attention in recent years for the potential application as nonvolatile memory. One of the tempting properties of RRAM is the multi-level memory, in which several resistance states can be obtained and each of them can be used to save information. In this paper, the electric-pulse-induced multi-level resistance switching of the Ag-La0.7Ca03MnO3-Pt heterostructures was studied. The multi-level resistance switching (MLRS) was observed in the switching from high to low resistance state (HRS→LRS) by applying electric pulse with various pulse voltages. The threshold pulse voltages of MLRS are related to the initial resistance values as well as the switching directions. On the other hand, the resistance switching behavior from low to high resistance states (LRS→HRS) shows unobvious MLRS. MLRS was explained by the parallel effect of multi-filament forming/rupture in the Ag/La0.7Ca0.3MnO3 interface layer. The present results suggest a possible application of Ag-La0.7Ca03MnO3-Pt heterostructures as multi-level memory devices.
Surface Morphologies and Optical Properties of Homoepitaxial ZnO Grown by Close-Spaced Chemical Vapor Transport
Authors: Abe Koji , Tokuda Tetsuya , Banno Yuta , Eryu Osamu 
Published: April 2011

AbstractChemical vapor transport (CVT) using carbon as a transporting agent is studied for homoepitaxial growth on O-polar ZnO substrates. To increase growth rate at high temperatures, we keep a substrate close to ZnO source powder. Surface smoothness and crystal quality of epilayers are remarkably improved by increasing a substrate temperature. Smooth surfaces are observed on the epilayer grown at substrate temperatures above 920°C.
Photocurrent Spectral Distribution and Relaxation in CdS/CdTe Heterojunctions
Authors: Vatavu Sergiu A. , Gasin Petru A. , Ferekides Chris S. , Caraman Iuliana M. 
Published: April 2011

AbstractPhotocurrent spectral distribution and relaxation in CdS/CdTe heterojunctions Sergiu Vatavu, Petru Gasin, Iuliana Caraman. Thin film CdS/CdTe solar cells have proved their importance in use as solar energy converters achieving 16.5 % efficiency. Thin film CdS/CdTe heterojunctions have been deposited by close spaced sublimation method (CSS), onto SnO2 covered glass plates (2õ2 cm2). The thickness of CdS and CdTe thin films was 0.3-1.6 m and 2.3-6.6 m respectively. For to enhance CdS/CdTe heterojunctions photoelectrical parameters and photosensitivity, the deposition procedure was followed by annealing in presence of CdCl2 at 420C for 15-60 min. Ni has been used as back contact to CdTe. After annealing, the photoelectrical parameters at 100 mW/ñm2 are: Uoc=0.73 V, Isc=21.7 mA/cm2, ff=0.43.The analysis of the photosensitivity for samples with different thicknesses of the component layers in the 78-293K temperature range showed, that the increase of the photoconductivity for photon energies ħw>1.9 eV is determined by the generation-recombination processes in CdSxTe1-x interface layer, and in the 1.42 eV-1.85 eV region, by light absorption mechanism in CdTe.At direct biases of the CdS/CdTe heterojunctions (2Uoc), the photocurrent spectral distribution is determined by the generation-recombination processes in CdS layer. The annealing of the heterojunction in presence of CdCl2 results in photocurrent increase more than one order of magnitude. CdS/CdTe at reverse biases, having a constant sensitivity in visible and near infrared spectral region, can be used in photometry as radiation detector.The analysis of the absorption spectra and the photocurrent spectral distribution at direct biases resulted in determination of the holes mean free path in CdTe layer, being equal to 1.05 mm.The ratio of the ambipolar diffusion coefficient and surface recombination velocity for CdS/CdTe interface is 0.3 m and the diffusion length is 0.6 m at 78K. The same parameters for Ni/CdTe interface are: 0.025 m and 0.05 m respectively.The phococurrent relaxation curves have been studied for illumination throught both sides of the heterojunctions at different biases, temperatures and wavelength, determining different penetration depths and materials excitation. Nonequilibrium charge carriers lifetime has been determined. The thermal annealing of the CdS/CdTe heterojunctions in presence of CdCl2 determine the nonequilibrium charghe carrier lifetime increase by more than one order of magnitude from 22 s up to 280 s.
Study of Recombination in Cu(In,Ga)Se2 Solar Cells by Time-Resolved Photoluminescence
Authors: Shirakata Sho , Nakada Tokio 
Published: April 2011

AbstractTime-resolved PL (TR-PL) measurements have been carried out on Cu(In1-x,Gax)Se2 (CIGS) thin films and solar cells to study the recombination of photo-generated minority carriers . Room temperature PL of both CIGS thin films and solar cells exhibited band-to-band transition for alloy composition x of 0-0.4, and PL decay curves have been utilized as a measure of carrier lifetime. The solar cell fabrication leads to the enhancement of band-to-band PL intensity, reduction of defect-related PL, and increase of PL decay time. It is noted that the increase in PL decay time has been observed in CIGS films after CBD-CdS deposition. Solar cells with high conversion efficiency are characterized by both high PL intensity and long PL decay time. The PL decay curve of CIGS solar cell is studied in terms of the alloy composition x. For small x, PL decay times of CIGS solar cells are almost independent of the emission photon energy. For large x, PL decay time depended on PL emission energy. he result suggests the change of the recombination mechanism in the CIGS solar cells with the change in the alloy composition x.
TEM study of Locations of Cu in CdTe Solar Cells
Authors: Yan Yanfa , Jones Kim , Zhou Jie , Wu Xuanzhi , Al-Jassim Mowafak 
Published: April 2011

AbstractUsing scanning transmission electron microscopy and nanoprobe X-ray energy-dispersive spectroscopy, we studied the locations of Cu in CdTe solar cells and test interfaces with intentionally introduced Cu sources. We found three primary locations of Cu: 1) back-contact region, 2) CdTe layer, and 3) CdTe/CdS junction areas. In the back-contact region, Cu diffused from back-contact can convert the Te-rich layer into Cu-Te compounds. In the CdTe layer, a higher concentration of Cu is found to distribute along grain boundaries, but not in twin boundaries and stacking faults. In the CdTe/CdS junction area, Cu is found uniformly in the CdS layer. However, significant segregation of Cu into CdS/TCO interfaces is also found.
Mechanical Properties of Indium Tin Oxide on Polyethylene Napthalate Substrate
Authors: Bhagat Shekhar , Zoo Y. , Han H. , Lewis J. , Grego S. , Lee K. , Iyer S. , Alford T. L. 
Published: April 2011

AbstractThis work investigates the mechanical properties of ITO on PEN substrates as a function of processing conditions, including rf power, substrate temperature, and substrate treatment. The best mechanical performance is obtained from high substrate temperature and low rf power. Plasma treatment gases also influence mechanical properties, with mixture of nitrogen and hydrogen gases producing the best results. This work provides an initial understanding of the impact of sputter process conditions on film's mechanical performance.
CdS/CdTe Solar Cells Made by High-Rate Magnetron Sputtering
Authors: Plotnikov Victor , Compaan Alvin 
Published: April 2011

AbstractThe dependence of deposition rate of CdTe film on deposition pressure and RF power has been studied. The optimum argon pressure was found to be 5 mTorr while the growth rate as a function of power is slightly superlinear. A deposition rate of 140 nm/min has been achieved which is five times faster than for our conventional deposition conditions. Films were characterized by means of X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). Pressure has been found to have a greater effect on film morphology than magnetron sputter power. Working devices have been made with 2-micron layers of CdTe deposited at different powers and 10 mTorr of argon pressure. The effect of different temperatures of CdCl2 post-deposition treatment on cell performance was studied. Efficiency of 11.8% with a 2-micron CdTe layer deposited at 133 nm/min was achieved.
The Phase Boundary Between β-Si3N4 and γ-Si3N4 at Elevated Temperatures and Pressures
Authors: Togo Atsuchi , Kroll Peter 
Published: April 2011

AbstractThe phase boundary between β-Si3N4 and γ-Si3N4 is investigated at high-pressure and high-temperature using first-principles lattice dynamics calculations within the quasi-harmonic approximation. We find a positive slope of the phase boundary. It turns out that the thermal expansion of the spinel-type γ-phase is larger than that of the phenacite-type β-phase. On the other side, pressure affects more the volume of β-Si3N4 than of γ-Si3N4, reflected in the higher bulk modulus of γ-Si3N4. The origin of the different temperature behavior of these phases, consequently, goes along with a larger volume dependence of the zero point energy in γ-Si3N4 in comparison to β-Si3N4.
Photoelectrochemical Etching of GaN Thin Films With Varying Carrier Concentrations
Authors: Leach Jacob H. , Özgür Ümit , Morkoç Hadis 
Published: April 2011

AbstractThe evolution of the surface morphology of unintentionally doped and Si-doped GaN samples subjected to photoelectrochemical (PEC) etching in the carrier-limited regime in aqueous KOH is reported. It was found that a nanoporous structure precedes whisker formation in samples in which high densities of whiskers ultimately form. Increasing the light intensity accelerated the rate of change of the surface morphology, but increasing the molarity of the KOH had no effect on the etching. Applying biases to the samples during etching also accelerated or decelerated the rates of change of the surface morphology. Thus, the surface morphology in the carrier-limited regime tends to only depend on parameters of the starting layers, as well as how much etching in total has occurred. The identification of variations in surface morphology at different times during PEC etching of GaN may have utility in that assorted nanopatterning of the GaN surface can be intentionally achieved in a controllable, large-scale, and inexpensive manner.
Pigment Analysis of Two Thai Banner Paintings
Authors: Giaccai Jennifer 
Published: April 2011

AbstractThe pigments used in two Thai banner paintings (phra bot) were examined using X-ray fluorescence (XRF), Fourier transform infrared microscopy (FTIR) and polarized light microscopy (PLM). The two paintings examined dated from the late 18th and the late 19th century. The paintings examined follow the trends observed on Thai wall paintings and manuscripts from the same time periods. Pigments identified include vermilion, iron oxide earths, red lead, lead white (hydrocerrusite), calcium carbonate, kaolin, Prussian blue, gamboge, artificial ultramarine, copper citrate and a copper-arsenic green.