bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of SiO2 Cap for Al Implant Activation in 4H-SiC
Authors: Zhao Feng , Islam Mohammad m , Chandrasekhar MVS , Sudarshan Tangali
Published: August 2010

The effect of using SiO2 capping layer during Al implant activation anneal on the performance of 4H-SiC P-i-N diodes has been investigated. Two sets of 4H-SiC pin diode samples, one with SiO2 cap and another with graphite cap, were annealed under high temperatures of 1500°C for activation after Al implantation at 650°C to form the p-type active region and the JTE region. The surface stoichiometry of annealed SiC was examined by x-ray photoelectron spectroscopy (XPS). Various material and device parameters including surface roughness, sheet resistance, minimum forward leakage current and maximum breakdown voltage have been extracted for comparison. The results show that SiO2 cap effectively protects the SiC surface during high temperature implant annealing.
Improved Inversion Channel Mobility in Si-face 4H-SiC MOSFETs by Phosphorus Incorporation Technique
Authors: Okamoto Dai , Yano Hiroshi , Kotake Shinya , Hirata Kenji , Hatayama Tomoaki , Fuyuki Takashi
Published: August 2010

We propose a new technique to fabricate 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) with high inversion channel mobility. P atoms were incorporated into the SiO2/4H-SiC(0001) interface by post-oxidation annealing using phosphoryl chloride (POCl3). The interface state density at 0.2 eV from the conduction band edge was reduced to less than 1 × 1011 cm−2eV−1 by the POCl3 annealing at 1000 °C. The peak field-effect mobility of 4H-SiC MOSFETs on (0001) Si-face processed with POCl3 annealing at 1000 °C was approximately 90 cm2/Vs. The high channel mobility is attributed to the reduced interface state density near the conduction band edge.
The Mechanism of Haze and Defectivity Reduction in a New Generation of High Performance Silicon Final Polishing Slurries
Authors: White Michael L , Romine Richard , Jones Lamon , Ackerman William
Published: August 2010

The mechanism of haze reduction during silicon polishing using a new generation of additives has been explored. These additives are thought to decrease haze by adsorbing to the wafer surface and increasing the activation energy of the reaction between the silanolates on the silica particle surface with the surface silicon. This leads to greater selectivity between the peaks and valleys resulting in a net decrease in surface roughness.
Non-selective, High Removal Rates STI Slurries Based on Lewis Acids Abrasives/Cationic Copolymers
Authors: White Daniela , Parker John C , Nagarajan R
Published: August 2010

In this presentation we will discuss polishing performance and related mechanistic aspects of several low solids, low or high pH slurries based on Lewis acids abrasives (TiO2, ZrO2, CeO2), activated by cationic homopolymers, and copolymers with acrylic functionality. In a typical example, a formulation containing 0.5% ZrO2 interacting with 75 ppm cationic copolymer, at pH = 4, resulted in a SiO2 removal rate increase of 34% and a nitride removal rate increase of 97%, as compared with the control lacking the cationic copolymer. We will provide a complex variety of analytical evidence and particle and wafers surface measurements (FT-IR, GPC, surface energy) in order to support our mechanistic hypotheses. We will show with this unique system that 1:1 selectivities of oxide and nitride can be achieved with high removal rates.
Mechanistic Investigations of Ruthenium Polishing Enabled by Heterogeneous Catalysis With Titania-based Slurries
Authors: White Daniela , Parker John C , Nagarajan R
Published: August 2010

Difficulties and challenges have been widely encountered in the chemical mechanical planarization (CMP) of noble metals used as diffusion barrier films due to hardness, chemical inertness and toxic oxidation products, in particular for Ru polishing. A commercial CMC Ru polishing slurry that successfully addressed the safety concerns was based on a high pH (8.4) polymer-treated-alumina-based multi-additive slurry containing complexing reagents (carboxylic acids and salts), corrosion inhibitors, surfactants, and hydrogen peroxide as a mild, non-aggressive oxidizer. Recently, our efforts had been redirected towards the development of a new generation of low pH barrier slurries based on an entirely new concept employing unique Lewis acid type abrasives. This class of materials is well known to be highly reactive in dielectrics polishing (ceria, zirconia, titania), but far less is known about their interactions with Ru, Cu or Ta.

In this presentation, we will elaborate the unexpected discovery that hard, chemically inert, noble metals such as ruthenium can be polished easily by virtually abrasive-free and/or oxidizer-free TiO2 based slurries. Of particular importance is the finding that the polymorphic phase of TiO2 (anatase or rutile), its surface chemistry (functional groups, Lewis acid/base character), pH induced surface modification and reactivity, can all mediate the abrasive particle's adsorption properties, catalytic activity and ultimately, its slurry polishing performance.
Organometallic Chemical Liquid Deposition (OMCLD) of Cu/SiO2 Films for 3D Filling in Microelectronic Applications
Authors: Fau Pierre , Piettre Kilian , Latour Virginie , Margeat Olivier , Barrière Clément , Colliere Vincent , Anceau Christine , Quoirin Jean Baptiste , Chaudret Bruno
Published: August 2010

The copper precursor N,N'-diisopropylacetamidinate has been decomposed at low temperature (80-110°C) in a liquid process under a moderate H2 pressure. Depending on the choice of the solvent, the process leads to a colloidal solution of well controlled copper nanoparticles or the deposition of composite Cu-SiO2 films on the surfaces. The latter layer is highly adhesive to silica surface, behaves as an active seed layer for electroless copper deposition and allows a conformal covering inside deep trenches.
Copper-sulfide Passivation Capping for Cu Interconnects
Authors: Cohen Uri
Published: August 2010

Copper-sulfide is proposed as a selective self-aligned passivation capping film on Cu lines, to improve the lines immunity against electromigration. Copper-sulfide is tenacious, having excellent adhesion (chemically bonded) to the underlying copper lines and strong adhesion to the overlying dielectric capping barrier. Contrary to other passivation schemes, Cu sulfidation is 100% selective. The sulfidation can be done by a wet or a dry process. A very thin copper-sulfide film (of about 25-100Å) will be required, and no significant increase of RC delay is expected.
Direct Measurement of Hot-spot Temperature in Flip-chip Solder Joints With Cu Columns Under Current Stressing using Infrared Microscopy
Authors: Chen Chih , Liang Yu Chun , Yao D. J.
Published: August 2010

In this study, the temperature map distribution in the Sn3.0Ag0.5Cu solder bump with Cu column under current stressing is directly examined using infrared microscopy. It is the radiance changes between the different materials of the surface that cause the unreasonable temperature map distribution. By coating a thin layer of black optical paint which is in order to eliminate the radiance changes, we got the corrected temperature map distribution. Under a current stress of 1.15 × 104 A/cm2 at 100℃C, the hot-spot temperature is 132.2℃ which surpasses the average Cu column temperature of 129.7℃C and the average solder bump temperature of 127.4 ℃. Thermomigration in solder may still occur under a large current stressing.
Theoretical Characterization of a Nanocrystal Layer for Nonvolatile Memory Applications
Authors: Leroy Yann , Armeanu Dumitru , Cordan Anne-Sophie
Published: August 2010

On the road to miniaturization, nanocrystal layers are promising as floating gate in nonvolatile flash memories. Although much experimental work has been devoted to the study of these new memory devices, only few theoretical models exist to help the experimentalists to understand the physical phenomena encountered and explain the behavior of the device.

We have developed a model based on the geometrical and physical properties of the elementary structure of a nanocrystal flash memory,i.e.one nanocrystal embedded in an oxide between the channel and the gate electrodes. To obtain a fine analysis of the observed phenomena, several specific hypotheses have been taken into account. Concerning the channel, the contribution of the subbands is explicitly included. In the case of an electrode with a quasi-continuum of energy levels, we replace the continuum by equivalent sets of 2D subbands in order to be able to isolate the energy range that really contributes to the charging/discharging of the nanocrystal. The properties of the materials (bulk band structure, dielectric permittivity, …) can be easily set as well as the geometrical specifications of the elementary structure (nanocrystal radius, tunnel and control oxyde thicknesses, …).

The behavior of a layer of nanocrystals is described according to a statistical approach starting from single nanocrystal results. This method allows us to take into account the fluctuations of geometrical parameters. Thus we are able to simulate various types of materials for the nanocrystals (Si, Ge, …), the oxide layer (SiO2, HfO2, …) and the electrodes, for both a single nanocrystal and layers of nanocrystals.
Analysis on Resistance Change Mechanism of NiO-ReRAM Using Visualization Technique of Data Storage Area With Secondary Electron Image
Authors: Kinoshita Kentaro , Makino Tatsuya , Takatoshi Yoda , Kazufumi Dobashi , Satoru Kishida
Published: August 2010

Both a low resistance state and a high resistance state which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the second electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.
Fabrication and Current-Voltage Characteristics of Ni Spin Quantum Cross Devices with P3HT:PCBM Organic Materials
Authors: Kaiju Hideo , Kondo Kenji , Basheer Nubla , Kawaguchi Nobuyoshi , White Susanne , Hirata Akihiko , Ishimaru Manabu , Hirotsu Yoshihiko , Ishibashi Akira
Published: August 2010

We have proposed spin quantum cross (SQC) devices, in which organic materials are sandwiched between two edges of magnetic thin films whose edges are crossed, towards the realization of novel beyond-CMOS switching devices. In SQC devices, nanometer-size junctions can be produced since the junction area is determined by the film thickness. In this study, we have fabricated Ni SQC devices with poly-3-hexylthiophene (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) organic materials and investigated the current-voltage (I-V) characteristics experimentally and theoretically. As a result of I-V measurements, ohmic I-V characteristics have been obtained at room temperature for Ni SQC devices with P3HT:PCBM organic materials, where the junction area is as small as 16 nm × 16 nm. This experimental result shows quantitative agreement with the theoretical calculation results performed within the framework of the Anderson model under the strong coupling limit. Our calculation also shows that a high on/off ratio beyond 10000:1 can be obtained in Ni SQC devices with P3HT:PCBM organic materials under the weak coupling condition.
Ferroelectric and Ferromagnetic Properties of Co-doped BiFeO3 Thin Films
Authors: Barrionuevo Danilo G , Singh Surinder P , Katiyar Ram S , Tomar Maharaj S.
Published: August 2010

Materials which possess electrical and magnetic coupling are of great interest for novel devices. Bi(Fe1-xCox)O3 (BFCO) material system was synthesized by solution route for various compositions and thin films were prepared by spin coating on Pt (Pt/Ti/SiO2/Si) substrates. Structural properties of the films were investigated by x-ray diffraction and Raman spectroscopy. X-ray diffraction patterns confirms intense (110) in BiFeO3 and Bi(Fe1-xCox)O3 with rhombohedra distorted perovskite structure without impure phase. Bi(Fe1-xCox)O3 films show week ferroelectric polarization and ferromagnetism at room temperature. Ferroelectric and ferromagnetic coupling could be attributed to the elimination of oxygen vacancies and increased stress in the crystal structure by partial replacement of Fe2+ ion by Co2+ ion.
PECVD Synthesis of Silicon Nanowires Assisted by Templates of Gallium Islands
Authors: Gewalt Annika , Kalkofen Bodo , Lisker Marco , Burte Edmund P.
Published: August 2010

In this study, we investigated the growth of silicon nanowires forced by small gallium droplet templates. Those gallium islands previously were deposited by a modified PECVD method. Two different delivery techniques of the trimethylgallium precursor (TMGa) were tested regarding their applicability. On the one hand standard liquid delivery was performed, on the other the precursor was transported by vapor draw out of the heated bubbler. The TMGa then was pulsed into the carrier gas flow. The effects on the deposited islands of both delivery methods were compared. As substrates <111> oriented p-doped silicon wafers were used. For the subsequent growth of the silicon wires similarly PECVD was used as growth method. Silane served as precursor. Argon and hydrogen were used as plasma enhanced gases. The effects of the Ga particles deposited by both process modes upon the generated wires were analyzed.
Atomic layer deposition ZnO film as seed layer for hydrothermal growth of ZnO nanorods
Authors: Li Xianglin , Cheng Chuanwei , Fan Hongjin
Published: August 2010

Atomic layer deposition (ALD) ZnO film as seed layer for growing aligned ZnO nanorods arrays is demonstrated. The effects of the deposition temperature and film thickness to the morphology of the ZnO nanorods are studied. The ALD is found to have its advantage over the conventional dip-coating method when being applied to three-dimensional (3D) substrates, as exemplified by the macroporous Si adn CNT arrays. As one example, the CNT-ZnO 3D hybrid nanostructures are obtained which might be useful for energy-related applications.
Magnetic State in Iron Hydride Under Pressure Studied by X-ray Magnetic Circular Dichroism at the FeK-edge
Authors: Ishimatsu Naoki , Matsushima Yasuharu , Maruyama Hiroshi , Tsumuraya Takao , Oguchi Tamio , Kawamura Naomi , Mizumaki Masaichiro , Matsuoka Takahiro , Takemura Kenichi
Published: August 2010

In order to study magnetic states in Fe-hydride under pressure, X-ray magnetic circular dichroism (XMCD) at the FeK-edge has been measured up to 27.5 GPa. As a result, hydrogenation from bcc-Fe to dhcp-FeH occurs within a narrow region of 3.2-3.8 GPa, which is clearly observed by the dichroic profile in dhcp-FeH differing from that in bcc-Fe. Influence of H atoms on Fe 3dand 4pelectronic states is discussed using the pressure-dependent XMCD and the first-principles calculation.
Formation of Methane Hydrates from Super-compressed Water and Methane Mixtures
Authors: Chen Jing-Yin , Yoo Choong-Shik
Published: August 2010

Understanding the high-pressure kinetics associated with the formation of methane hydrates is critical to the practical use of the most abundant energy resource on earth. In this study, we have studied, for the first time, the compression rate dependence on the formation of methane hydrates under pressures, using dynamic-Diamond Anvil Cell (d-DAC) coupled with a high-speed microphotography and a confocal micro-Raman spectroscopy. The time-resolved optical images and Raman spectra indicate that the pressure-induced formation of methane hydrate depends on the compression rate and the peak pressure. At the compression rate of around 5 to 10 GPa/s, methane hydrate phase II (MH-II) forms from super-compressed water within the stability field of ice VI between 0.9 GPa and 2.0 GPa. This is due to a relatively slow rate of the hydrate formation below 0.9 GPa and a relatively fast rate of the water solidification above 2.0 GPa. The fact that methane hydrate forms from super-compressed water underscores a diffusion-controlled growth, which accelerates with pressure because of the enhanced miscibility between methane and super-compressed water.
Correlating Small Angle Scattering Spectra to Electrical Resistivity Changes in a Nickel-base Superalloy
Authors: Whelchel Ricky L , Kelekanjeri V. Siva Kumar G. , Gerhardt Rosario , Ilavsky Jan , Littrell Ken C.
Published: August 2010

Waspaloy specimens aged at 800°C from 0.5h to 88.5h were evaluated via small angle neutron scattering (SANS), ultra small angle X-ray scattering (USAXS), electrical resistivity, and SEM. The average γ' precipitate size and volume fraction, obtained from modeling the small angle scattering data, was used to calculate a figure of merit of electron scattering. This figure of merit is designed to correlate the electron scattering ability of the material to the precipitate microstructure. The USAXS data shows a secondary precipitate population at smaller diameters that is absent from the SANS data, since the SANS measurements were not obtained at high enough values of Q. It is believed that this secondary population makes the USAXS-derived figure of merit more sensitive to the actual measured resistivity response than the SANS-derived values; however, the SANS derived primary precipitate sizes are believed to more accurate due to a larger sample volume.
Point Defects and Swelling Induced in Yttria-stabilized Zirconia by Swift Heavy Ion Irradiations
Authors: Costantini Jean-Marc , Beuneu François
Published: August 2010

We present a study of point-defect creation in yttria-stabilized zirconia (ZrO2: Y) or YSZ exposed to various heavy ions (from C to U) covering an energy range from 100 MeV to several GeVs. It is concluded that F+-type centers (involving singly-ionized oxygen vacancies) are produced by elastic-collision processes. The ion-induced out-of-plane expansion is found to be small (< 0.2%) and to increase linearly as a function of the average F+-type center concentration with a large slope compatible with small oxygen vacancy clusters. The large defect volume and <100> axial symmetry of the F+-type centers hint that these color centers might actually be divacancies (i.e. F2+centers).
Contribution of Electronic Energy Deposition to the Atomic Cascade Damage in Nanocrystals
Authors: Backman Marie , Djurabekova Flyura , Pakarinen Olli H , Nordlund Kai , Toulemonde Marcel
Published: August 2010

Using Molecular Dynamics we study the role of electronic excitations in the radiation damage caused by an energetic ion in Ge nanocrystals embedded in amorphous SiO2. The electronic effects are included as heating along the ion path modeled by the thermal spike model. In an ion energy regime where the electronic stopping power is larger than the nuclear, we find that the electronic effects enhance the defect creation significantly. We conclude that the electronic excitations below the track production threshold due to an energetic ion cannot be disregarded as a source of radiation damage.
AFM Study of the Fluence-Dependent Modification of the Surface of YSZ Due to Argon Ion Irradiation
Authors: Hawley Marilyn E. , Usov Igor O. , Won Jonghan , Sickafus Kurt E.
Published: August 2010

Yittria stabilized zirconia (YSZ) has long been of interest as a promising material for nuclear energy applications. It is the cubic form of zirconium oxide stabilized at room temperature by the addition of yttria. Previous studies of radiation damage in YSZ focused primarily on microstructural changes in the bulk or in the near surface layer whereas irradiation induced changes on the surface received little attention. Here we use atomic force microscopy, AFM, to study the fluence-dependent generation of surface modifications to YSZ due to 150 keV Ar+ ion implantation at fluences from 3×1015 to 1×1017 ions/cm2. The microstructural changes in the near surface region were previously investigated by Rutherford backscattering spectrometry in channeling geometry (RBS/C). Further, we investigated implantation in (100), (110), and (111) oriented single crystals of YSZ to explore differences in crystal orientation sensitivity to damage to ion irradiation. At the highest fluence, a dense packing of large round surface hillocks was observed. The ion induced surface modifications revealed by AFM differ slightly from the bulk lattice damage measured by RBS, although both indicate that under these implantation conditions, the (110) oriented crystal shows the most radiation damage resistance. The mean size of the hillocks scaled with concentration of implanted Ar atoms.
Surface Deformation Nanostructures and Stress Corrosion Crack Precursors Originating from Surface Grinding
Authors: Olszta Matthew , Thomas Larry , Bruemmer Stephen
Published: August 2010

Stress corrosion cracking (SCC) in light water reactor components has long been studied from a post mortem perspective, yielding insights into water chemistries and effects on crack propagation. Analysis of a cracked component does not effectively provide information on the corrosion events or on SCC initiation. It is important that microstructures of these early stages be understood because the original surface of the component formed during fabrication is often not the final surface condition that is exposed to reactor water. Pre-service grinding of reactor components and welds is performed for a variety of reasons, from aesthetics to preparation for non-destructive testing. It is this final surface microstructure that often controls SCC initiation. Surface and near-surface characteristics have been investigated in 304SS metal coupons on which controlled grinding was performed. These examinations indicate the extent of subsurface microstructural damage before high-temperature water exposure. Analytical electron microscopy techniques have been used to gain insights into possible surface precursors to corrosion damage and SCC initiation. Nanocrystalline grains were commonly found at the surface in lightly ground to heavily abraded materials within the first ˜0.5-10 ųm along with high dislocation densities, twinning and lath structures.
Electrospray ionization mass spectrometry of the cerium(III)-phosphomolybdate complex (NH4)11Ce(PMo11O39)2
Authors: Bray Travis Henry , Copping Roy , Shuh David K. , Gibson John
Published: August 2010

Electrospray ionization quadrupole ion trap mass spectrometry of the ammonium lanthanide(III) phosphomolybdate complex (NH4)11Ce(III)(PMo11O39)2 has been conducted revealing the Ce-POM complexes H2Ce(III)P2Mo22O753- and Ce(III)PMo11O382- as the primary Ce species in 10 mM solutions. From the complex isotopic fingerprints produced through the assembly of multiple molybdenum atoms, a transition metal with seven naturally occurring isotopes, the identities of larger ions were confirmed via successive collision induced dissociation (CID) studies of the gas phase ions. The result of these CID studies was the production of smaller ions with reduced molybdenum content, allowing for comparison between calculated and experimental isotopic distributions. CID studies also provided insights into favored fragmentation pathways. These studies provide a basis to explore speciation and ESI behavior of actinide cluster complexes.
5f Electronic Structure and Fermiology of Pu Materials
Authors: Joyce John J. , Durakiewicz Tomasz , Graham Kevin S. , Bauer Eric , Moore David P. , Mitchell Jeremy N. , Kennison John A. , McCleskey T Mark , Jia Quanxi , Burrell Anthony , Bauer Eve , Martin Richard L. , Roy Lindsay , Scuseria Gustavo E.
Published: August 2010

We examine the electronic structure of δ-Pu, PuCoGa5, and PuO2 using high resolution as well as angle-resolved photoelectron spectroscopy. The fermiology of the strongly correlated metals δ-Pu and PuCoGa5 is investigated by determining the primary quasiparticle peak position with respect to the Fermi energy as well as the crystal momentum dependence of this peak for PuCoGa5. For the Mott insulator PuO2, the photoemission results are compared against the hybrid functional calculations and the prediction of significant covalency, is found to be reasonable.
Plutonium Environment in Lanthanide Borosilicate Glass
Authors: Stefanovsky Sergey , Shyriaev Andrey , Zubavichus Yan V. , Marra James C.
Published: August 2010

Two lanthanide borosilicate (LaBS) glasses containing 9.5 and 5.0 wt.% PuO2 prepared at 1500 °C consisted of a vitreous phase and minor crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2) and britholite-type phases. X-ray absorption spectra of Pu LIII edge in the as-prepared and stored for various periods LaBS glasses were recorded, analyzed and compared with the spectra of crystalline PuO2. Pu in the as-prepared glass existed in predominantly tetravalent form (Pu4+ ions) but its storage in air results in partial oxidation as was seen from shift of peak energy values. In the structure of the as-prepared glass, Pu4+ ions had a co-ordination number (CN) close to 6 (˜6.3) and were located within the axially squeezed octahedra with five equidistant oxygen ions at a distance of 2.265±0.015 Å and one – at shorter distance (2.130±0.010 Å) from the Pu4+ ion. The Pu—Pu(M) distance (second co-ordination shell) was 3.675±0.015 Å. “Aging” of the LaBS glass with transformation of some fraction of Pu into penta- or/and hexavalent form was accompanied by a structural transformation.
Design and Synthesis of One and Two Dimensional Thermoelectric Nanomaterials Composed of Bismuth, Antimony, and Tellurium
Authors: Mott Derrick , Thuy Nguyen Thi Bich , Mai Nguyen Thanh , Maeda Youjiro , Phan Thuy Linh Tran , Koyano Mikio , Maenosono Shinya
Published: August 2010

With the advent of nanotechnology, the field of thermoelectric (TE) materials has been re-invigorated with many recent advances towards materials with high thermoelectric efficiency (dimensionless figure of merit, ZT). The realization of such materials opens up new avenues to the creation of devices that can be used in freon-less refrigeration, micro-electronic cooling, or for harnessing lost heat energy from sources such as car engines. In our own research work, we have successfully synthesized thermoelectric nanoscale materials composed of bismuth, antimony, and tellurium. By using a wet chemical thermal reduction procedure, we were able to create bismuth, antimony, and tellurium composite particles. What's more, by employing different molecular encapsulating agents in the synthesis, we were able to control the resulting shapes of the nanomaterials, resulting in both one and two dimensional bismuth, antimony, and tellurium nanoparticles. The one dimensional nanowires exhibit a micron scale length and ∼20-50nm diameter, while the two dimensional nanodiscs exhibit a diameter of ∼100nm and a thickness of ∼25nm. The unique morphology of these materials make them ideal candidates for processing into functional thermoelectric devices. This paper focuses on our recent study of the synthesis of bismuth, antimony, and tellurium composite nanomaterials of a nanowire and nanodisc morphology, which was directed by the capping agents used in the synthesis. Part of our preliminary study includes analysis of the thermoelectric efficiency of the materials. The resulting nanomaterials are characterized using techniques such as HR-TEM, XPS, XRD, and SEM the results of which provide insight into the design and synthesis of nanoscale materials with enhanced thermoelectric properties.
Thermoelectric Figure of Merit Calculations for Nanowires –The Moderate Confinement Regime
Authors: Cornett Jane , Rabin Oded
Published: August 2010

We report room temperature ZT calculations for silicon and indium antimonide nanowires of varying radii. Interestingly, some systems deviate significantly from the anticipated trend of ZT vs. radius. The InSb results are particularly remarkable due to the non-monotonic relationship seen between n-type ZT and wire radius; where typically we expect to see only a decrease with increasing radius, for InSb ZT increases between 20 and 100 nm wire radii. This is thought to be due to the high level of degeneracy of subbands for larger nanowire radii. These results indicate that the monotonic relationship between ZT and wire radius observed under strong confinement conditions cannot be assumed, but must be tested on a case-by-case basis for each materials system.
Impact of Dopants on the PbTe Thermoelectric Efficiency
Authors: Xiong Ka , Gupta Rahul P , White John B , Gnade Bruce , Cho Kyeongjae
Published: August 2010

We investigated the impact of doping group III elements (Al, Ga, In and Tl) on the electronic structure of PbTe by first principles calculations. The impurity-induced defect level changes with respect to the charge state of the impurity. We find that among the four elements, Tl is the best candidate for the enhancement of thermoelectric efficiency, consistent with the experimental data.
Indentation Testing of Bulk Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 Half-Heusler Alloys
Authors: Verges Melody A , Schilling Paul J , Germond Jeffrey D , Upadhyay Puja , Miller William K , Takas Nathan J. , Poudeu Pierre F. P.
Published: August 2010

Indentation tests were performed to assess the influence of compositional changes on the mechanical properties of several half-Heusler compounds with the general composition Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 (x=0.0,0.1,0.3,0.5,0.7). These samples were synthesized by high temperature solid-state reactions and were consolidated by hot-pressing. Indentation measurements were obtained using both microhardness testing (Vickers) and depth-sensing nanoindentation. These measurements were used to determine the microhardness and the elastic modulus of each half-Heusler compound. The Vickers hardness values were found to range between 876 and 964. A slight increase in hardness was observed with the addition of iridium. The elastic stiffness values ranged from 229 GPa to 246 GPa. Here, a slight decrease in stiffness was observed with the addition of iridium.
Microstructure Investigation of Non-equilibrium Synthesized Filled Skutterudite CeFe4Sb12
Authors: Zhou Juan , Jie Qing , Li Qiang
Published: August 2010

We have prepared a variety of filled skutterudites through non-equilibrium synthesis by converting melt-spun ribbons into single phase polycrystalline bulk under pressure. In general, better thermoelectric properties are found in these samples. In this work, we performed microstructure characterization of non-equilibrium synthesized p-type filled skutterudite CeFe4Sb12 by X-ray diffraction, scanning electron microscopy and transmission electron microscopy in order to understand the structural origin of the improved thermoelectric properties. It is found that the non-equilibrium synthesized samples have smaller grain size and cleaner grain boundaries when compared to the samples prepared by the conventional solid-state reaction plus long term annealing. While smaller grain size can help reduce the lattice thermal conductivity, cleaner grain boundaries ensure higher carrier mobility and subsequently, higher electrical conductivity at the application temperatures.
Correlation of Microstructural Properties With Thermoelectric Performance of Bi0.5Sb1.5Te3 Films Fabricated by Electroplating
Authors: Koukharenko Elena , Li Xiaohong , Kuleshova Jekaterina , Fowler Marcel , Frety Nicole , Tudor John M , Beeby Steven P , Nandhakumar Iris , White Neil M
Published: August 2010

This study shows for the first time, the correlation between the microstructural properties (chemical composition and its homogeneity) and the thermoelectric properties for p-type Bi0.5Sb1.5Te3 electroplated films (10-15 μm thickness). High microstructural quality of Bi0.5Sb1.5Te3 electroplated films (a close to stoichiometry chemical composition with its high homogeneity elements distribution) was achieved by using an additive in the plating solution (sodium ligninsulfonate) as a surfactant agent. A fine-grained microstructure of 280 nm to 1μm has been observed for these materials, which half that of the plated films without a surfactant. The thermoelectric properties of electrodeposited Bi0.5Sb1.5Te3 films obtained without microstructural optimisation, show modest Seebeck coefficient values of 20-120 μm/K, electrodeposited film with an optimised microstructure exhibits very high values of Seebeck coefficient of 220-300 μm/K.
Electrically Active and Electrically Inactive 3d Transition Metal Centers in Si
Authors: Estreicher Stefan K , Backlund Daniel J
Published: August 2010

Systematic first-principles calculations on transition metal (TM) impurities of the 3d series in Si have been performed. The equilibrium sites, migration energies, electrically-active gap levels, charge and spin states are predicted. While the properties of the isolated interstitials are experimentally well-known, much less experimental information is available about the consequences of their interactions with vacancy-like defects. We discuss here the properties of isolated interstitial Ti, Fe, and Ni, their interactions with vacancies and divacancies, the properties of the resulting substitutional impurities, and of the TM-divacancy {V-TM-V} complexes. In equilibrium, interstitial Ti, Fe, and Ni do not become substitutional, but a number of processing steps commonly used in PV manufacturing introduce highly mobile vacancies into the bulk. These vacancies strongly interact with interstitial TMs. At the substitutional site, Ti, Fe, and Ni have very different electrical properties than at the tetrahedral interstitial site. In particular, the electrical activity (and stable spin state) of Ti and Fe are greatly reduced, suggesting that the passivation by vacancies plays an unrecognized role during a variety of high-temperature processes.
Effects of 2nd Phases, Stress, and Na at the Mo/Cu2ZnSnS4 Interface
Authors: Johnson Jeffrey L. , Nukala Haritha , Bhatia Ashish , Oo W.M. Hlaing , Rieth Loren W , Scarpulla Michael A , Lund Elizabeth A
Published: August 2010

Cu2ZnSnS4 (CZTS) is an alternative material to Cu(In,Ga)Se2 (CIGSe) for use in thin film photovoltaic absorber layers composed solely of commodity elements [1,2]. Thus, if similar material quality and performance can be realized, its use would allow scale-up of terrestrial thin film photovoltaic production unhindered by material price or supply constraints. Here we report on our research on the deposition of CZTS by RF sputtering from a single CZTS target and co-sputtering from multiple binary sources on Mo-coated glass. We find some samples delaminate during post-sputtering furnace annealing in S vapor. Samples on borosilicate glass (BSG) delaminate much more frequently than those on soda-lime glass (SLG). We investigate the influences of the formation of frangible phases such as MoS2 at the CZTS/Mo interface and residual and thermal mismatch stress on delamination. We implicate fracture in a layer of MoS2 as the mechanism of delamination between the Mo and CZTS layers using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Wafer curvature measurements show significant (˜400 MPa) deposition stress for minimally optimized Mo deposition; however nearly stress-free Mo layers with good adhesion can be deposited using a multi-step Mo deposition recipe. Co-sputtering CZTS adds 100 MPa of stress on both BSG and SLG, however delamination is nearly absent for samples deposited on low-stress Mo layers. We investigate metallic diffusion barrier layers to prevent the formation of MoS2 at the interface. Lastly we discuss the importance of removing Mo oxide by sputter etching before CZTS deposition and its effects on adhesion and series resistance.
Effect of Li3+ Ion Irradiation on Ionic Transport Properties of Complexed Polymer Electrolytes
Authors: Gupta Prem Narain , Prajapati Govind Kumar , Roshan Rupesh
Published: August 2010

Swift heavy ion (SHI) irradiation effects on ionic conduction in the PVA-H3PO4 polymer electrolyte films have been investigated due to its variety of applications in electrochemical devices. Polymer electrolytes films are irradiated with 50 MeV Li3+ ions having five different fluences viz. 5x1010, 1011, 5x1011, 1012 and 5x1012 ions/cm2. It is observed that irradiation of the polymer electrolyte films with swift heavy ions shows enhancement in conductivity at lower fluences and decrease in conductivity at higher fluences. It appears that below the critical fluence, swift heavy ion irradiation increases the diffusivity of Li+ ion in the polymer electrolyte which provides larger pathways for ionic transport throughout the system. The temperature dependence of electrical conductivity variation has been used to compute the activation energy involved in conduction process.
Proton Transfer in Perfluorosulfonic Acid Functionalized Carbon Nanotubes
Authors: Habenicht Bradley F , Paddison Stephen J , Tuckerman Mark
Published: August 2010

Proton dissociation and transfer are investigated with ab initio molecular dynamics (AIMD) simulations of carbon nanotubes (CNT) functionalized with perfluorosulfonic acid (-CF2SO3H) groups with 3 H2O/–SO3H. The CNT systems were constructed both with and without fluorine atoms covalently bound to the inner walls to determine the effects of the presence of fluorine on proton dissociation, hydration, and stabilization. The results of the AIMD trajectories show that decreasing the separation of sulfonic acid groups increases the propensity for proton dissociation. The simulations also revealed that the dissociated proton was preferentially stabilized as a hydrated hydronium (H3O+) cation in the CNT systems with the fluorine. This feature is attributed to the fluorine atoms providing a localized negative charge that promotes hydrogen bonding of the water molecules coordinated to the central hydronium ion. The hydrated H3O+ ion differed from a traditional Eigen cation (H9O4+) as it donated hydrogen bonds to sulfonate oxygen atoms, as well as water molecules.
PEG-based bioactive hydrogels crosslinked via phosphopantetheinyl transferase
Authors: Mosiewicz Katarzyna , Johnsson Kai , Lutolf Matthias P.
Published: August 2010

State-of-the-art tissue engineering strategies increasingly rely on the performance of bioactive hydrogels formed via cell-friendly crosslinking reactions. Enzymatic reactions possess ideal characteristics for such applications, but they are currently still underexplored in biomaterials design. Here we report the development of hybrid bioactive hydrogels formed via a posttranslational modification reaction using phosphopantetheinyl transferase (PPTase). PPTase was shown to catalyze the covalent crosslinking of CoenzymeA-functionalized poly(ethylene glycol) (PEG) multiarm macromers and recombinantly produced acyl carrier protein (ACP) dimers. Crosslinking kinetics and physicochemical properties of PPTase hydrogels were characterized. Proof-of-principle experiments demonstrate the successful covalent bio-functionalization of gels with a CoA-derivatized cell adhesion peptide. Polymerization of gels in the presence of primary mammalian cells was shown to result in no loss in cell viability compared to a well established, chemically crosslinked gel system.
Concentrated crystallization of closely packed colloidal crystal films from aqueous suspension immersed in silicone oil
Authors: Fudouzi Hiroshi , Sawada Tsutomu , Brush Lucien
Published: August 2010

Colloidal crystals have been attracting much attention due to their novel use as 3D-photonic crystals and to their structural color. We have been developing a method for the colloidal crystal growth of opal films immersed in silicone oil. This method is one of the evaporative self-assembly techniques for opal films from colloidal particle suspensions. Understanding the mechanism of the process is important to assure the coating of high-quality opal thin films. The colloidal crystallization from suspension was observed with a long working distance optical microscope and Bragg's diffraction peaks were measured with a miniature fiber optic spectrometer. The transition from a non-crystalline to a crystalline phase is observed within a region between the disordered colloidal suspension and the colloidal crystal film. Within this region, that spans a distance of about 400μm, the lattice of the colloidal crystal reduces until it transitions to the close-packed structure.
Mechanics of SFRC under tension, part I: analytical study
Authors: Ghosh S. , Bhattacharjya S. , Chakraborty S.
Published: August 2010

This is the first of a two-part paper involving a fundamental study of mechanics of short-fibre-reinforced concrete under tension. The theory derived in this paper is validated in a second paper using experimental investigation. The composite material approach, which is based on micromechanics, is employed to describe the phenomenon in terms of constitutive properties of fibre, matrix, fibre–matrix interface and their proportioning. The tensile stress–strain behaviour of short-fibre-reinforced concrete is described with four distinct stages, namely the elastic stage, the stage of closed isolated crack development, and the stages of through-crack development both in the absence of fibre rupture and in the presence of fibre rupture. The analytical development does not require pre-assumed composite behaviour such as peak load, initial tangent modulus etc. The formulation is validated using experimental investigation, supplemented by the results of the available models in the existing literature. Given the extent of the study, it was decided to present the entire work in two parts. The general theoretical development is presented here in part I and the comparisons with test results are presented in the companion paper, as part II.
Web crushing strength of reinforced concrete beams with pre-existing cracks
Authors: Pimanmas A.
Published: August 2010

This paper reports the effect of pre-existing cracks on the web crushing strength of reinforced concrete beams. Two experimental series were conducted. The first series involved the test of four slender beams with large amounts of stirrups. The second series involved the test of five deep beams without transverse reinforcements. In both series, vertical pre-cracks were created in the shear span of the specimens by means of reversed flexural loading. Then, the beams were loaded in shear to fail by web crushing. The width of pre-existing cracks was a main parameter in the test. Both experimental series demonstrated that the pre-existing cracks reduced the shear strength of the beams. The reduction in shear capacity varied with the width of pre-existing cracks. The strength degradation mechanism was proposed to comprise (a) the reduction in effective contact area and (b) the apparent strength degradation owing to micro-cracking damages. Based on these two physical mechanisms, a simple strength degradation model has been formulated. The first mechanism was represented by an effective contact area factor adopted from previous researches. The second mechanism was represented by a damage parameter which was derived from the test data. The model was then used to calculate the degraded compressive strength of concrete for a state of cracking damage defined by the width and spacing of pre-existing cracks. A strut-and-tie model was also constructed to analyse the specimens in both series using the degraded compressive strength obtained from the model. The strut-and-tie prediction closely matched experimental shear capacities of specimens in both series with the difference from the test less than around 4–5%. The research highlights the significance of incorporating degraded concrete compressive strength into the structural analysis and investigation of concrete members.
68.3: Dual‐Sided Slim LCD Display System with UV Excited Flat Backlight
Authors: Huang Hsin‐Tao , Tsai Chuang‐Chuang , Huang Yi‐Pai , Hsiao Chun‐Chung , Chen Sung‐Po , Peng Yi‐Hsing , Chang Win‐Chi
Published: August 2010

Dual‐Sided LCD displays are ideally suited for the public information display (PID) application. The UV excited flat lighting (UFL) was successfully demonstrated to perform dual‐Sided illumination with the features of flat lighting, uniform luminance and high brightness on a 42” TFT‐LCD display. Compared to conventional CCFL or LED lighting source, UFL is superior for the dual‐Sided display application with its slim backlight module profile and power saving.
68.5L:Late‐News Paper: Monolithic Block‐Wised Light Guide with Controlled Optical Crosstalk for Field‐Sequential Color/Scanning LCD
Authors: Käläntär Kälil , Okada Masafumi , Ishiko Hiroyuki
Published: August 2010

A monolithic functional light guide is characterized with seven horizontal recessed V‐grooves on the back surface in order to realize a block‐wised scanning backlight for field‐sequential color LCD. Each V‐groove functions as semi partition between the consecutive blocks and its height controls the crosstalk between the blocks. To reduce the dispersion and enhance the luminance, the light guide is characterized with micro prism arrays on the light injection surface, the back surface, and front surface. Finally the monolith is combined with a single TIR prism film to direct the enhanced light toward the surface normal on each block.
P‐1: Self‐Modulated Amorphous Front and Back Light Sensors with Wide Dynamic Range
Authors: Kuo Yan‐Fu , Yu Teng‐Jui , Yen Shao‐Wen , Tai Ya‐Hsiang
Published: August 2010

Source gate and partial floating dual gate structure of a‐Si TFTs and its illumination effect are used to make front and back light sensors. The proposed system employs novel device to sense illumination for wide dynamic range. It's expected the integration of sensing system onto the panel without extra process.
P‐5: Self‐Release Nickel Induced Lateral Crystallized (SR‐NILC) Low Temperature Polycrystalline Silicon Films and Thin Film Transistors
Authors: Zhao Shuyun , Liu Zhaojun , Wei Zhou , Meng Zhiguo , Wong Man , Kwok Hoi Sing
Published: August 2010

Nickel induced crystallization of a‐Si with a self‐release inducing source was studied. Three main factors affecting the crystallization rate were investigated. The new source possesses an effect of nickel self‐release and the crystallized poly‐Si has obviously lower nickel residua. The p‐channel thin film transistors (TFTs) based on the SR‐NILC poly‐Si film showed lower off‐state current (Ioff) and gate induced drain leakage (GIDL).
P‐14: AM‐OLED Pixel Circuits Based on a‐InGaZnOThin Film Transistors
Authors: Chen Charlene , Kanicki Jerzy , Abe Katsumi , Kumomi Hideya
Published: August 2010

In this paper, we investigated the application of amorphous In‐Ga‐Zn‐O (a‐InGaZnO) thin film transistors (TFTs) to active‐matrix organic light emitting display (AM‐OLED) pixel circuits. SPICE model of a‐InGaZnO TFTs was developed based on experimental data. Several pixel circuits were explored, and the potential advantages of using a‐InGaZnO TFTs were discussed.
P‐30: Temporal Sampling Parameters and Motion Portrayal of Television
Authors: Sugawara Masayuki , Omura Kohei , Emoto Masaki , Nojiri Yuji
Published: August 2010

The relationship between the temporal sampling parameters and motion portrayal of television images was studied. Subjective evaluation tests revealed the parameter values for perceptible and acceptable limits of motion blur. The stroboscopic effect was also evaluated for various sampling frequency and aperture by using the test materials similar to those used in broadcast programs.