bluuebunny/crossref_metadata_2025 huggingface dataset:
Interface quality of atomic layer deposited La-doped ZrO2 films on Ge-passivated In0.15Ga0.85As substrates
Authors: Molle Alessandro , Brammertz Guy , Lamagna Luca , Spiga Sabina , Meuris Marc , Fanciulli Marco
Published: August 2010

La-doped ZrO2 thin films were grown by O3-based atomic layer deposition on III-V (GaAs, In0.15Ga0.85As) substrates. The direct oxide deposition and the insertion of a Ge passivation layer in between the oxide and the substrate are compared in terms of the resulting density of interface traps. An improved electrical quality of the Ge-passivated interfaces concerning the energy region close to the conduction band edge in the semiconductor band-gap is demonstrated through conductance maps at various temperatures and it is attributed to Ga-related interfacial defects.
The Effect of Passivation SiON Layer on the Data Retention Reliability of NAND Flash
Authors: Jang Younggeun , Lee Kwangwook , Kim Eunsoo , Cho Jonghye , Shim Jungmyoung , Kim Sangdeok , Kim Junggeun , Park Sangwook , Lee Byungseok , Kim Jinwoong
Published: August 2010

Data retention is one of the major device reliabilities of NAND Flash memory. We found that the lower Refractive Index (RI) of the Passivation Silicon Oxynitride (SiON) layer deposited by PECVD, the better data retention behavior was achieved. The hydrogen content and the stress analysis of the films are analyzed to find out which is more important in this case. Generally, when the RI of SiON decreases, both parameters also decrease, so it is impossible to find out which parameter is major factor of data retention. To analyze the effects of two parameters separately, we applied two conditions which had the same H contents but quite different stress values. The final data retention levels are same in both conditions. In addition, even if the layer has the same H content, the retention characteristic is changed by how hydrogen is bonded in the film. In conclusion, the data retention characteristic can be explained by mobile ions generated by the hydrogen weakly bonded in PECVD SiON films in our experiment.
Degradation of Current Gain for Ion Implanted 4H-SiC Bipolar Junction Transistor
Authors: Watabe Yuki , Tajima Taku , Nakamura Tohru
Published: August 2010

Degradation of current gain for ion implanted 4H-SiC bipolar junction transistor is described. The influence of bandgap-narrowing to the collector and base currents of the transistor was investigated using ISE-TCAD simulator. Simulated results show good agreement with the measured results, which show that the common emitter current gain of 3.9 is obtained at a maximum base concentration of 2×1017/cm3 and a maximum emitter concentration of 4×1019/cm3 for ion implanted 4H-SiC BJTs.
Development of SiO2 Dielectric Thin Film Prepared by the Low-temperature Solution Process
Authors: Kodzasa Takehito , Uemura Sei , Suemori Kouji , Yoshida Manabu , Hoshino Satoshi , Takada Noriyuki , Kamata Toshihide
Published: August 2010

It is mostly important to develop the fabrication technology of the dielectric thin film with high insulation performance and surface flatness by large-area printing process. We have developed a technique to fabricate a silicon dioxide (SiO2) dielectric thin film by the low temperature solution process. The thin film prepared by about 170°C showed excellent dielectric performance with high resistivity in the order of 10 to the 16 Ωcm and surface flatness with the same degree of thermal oxidized SiO2 thin film on the silicon wafer (RMS=0.15nm). In addition, it is showed that the production of thick film of SiO2 with high dielectric performance and surface flatness is possible by applying over-coating technique. These indicate that this SiO2 production technique is greatly useful for the large-area printed electronics technology.
Parametric CFD Optimization of an APCVD Glass Coating Deposition Module
Authors: Wei Jiuan , Zhang Wei , Salagaj Tom , Strobl Karlheinz
Published: August 2010

Atmospheric Pressure Chemical Vapor Deposition (APCVD) thin film coating process is one of the most cost efficient large area thin film coating solutions presently available on the market and can be up to 2.5 times lower in cost compared with a low pressure sputtering system. Advanced materials such as transparent conductive oxides (TCO) used for solar panel manufacturing and for energy saving (Low-E) windows already have been deposited with APCVD Tools incorporating one or more deposition modules. Thin films such as SiO2, TiO2 and F: SnO2, etc have been successfully deposited onto glass sheets. However further improvement in material efficiencies and operational cost reductions are needed to satisfy the growing demand for such highly customized materials. It is also desirable in the future to be able to deposit other material films which traditionally have not yet been available on this lower cost APCVD manufacturing platform, such as zinc oxide (ZnO).

To investigate in a quantitative manner the improvement potential for the traditional APCVD deposition module design solution we performed a multidimensional computational fluid dynamics (CFD) parametric study using ANSYS FLUENT V12. As a baseline deposition module design we used a commercially available APCVD deposition module originally developed by Watkins-Johnson for SiO2 deposition trench fill of Si wafers from TEOS, O2 and Ozone from which we could locate in previously published papers for both experiment and CFD modeling results. The CFD software enabled us to perform a full parametric APCVD deposition module design study and allowed us to quantify the efficiency and throughput gains/losses of a wide variety of design change options. The main driver for this study was to learn in a quantitative, cost efficient and time efficient manner about what system design modifications have the potential for significant precursor efficiency increase and/or deposition throughput gain for a particular APCVD deposition process. The results of this study will be utilized to accelerate our proprietary, next generation Off-line and On-line CVDgCoat™ APCVD platform development.
New Copolymers Based on Acenaphto[1,2-b]thieno[3,4-e]Pyrazine for Transistor and Solar Cell Applications
Authors: Boudreault Pierre-Luc T. , Miyaki Nobuyuki , Mondal Rajib , Tang Ming Lee , Bao Zhenan , Leclerc Mario
Published: August 2010

We will show the synthesis of new donor-acceptor copolymers based on 2,7-carbazole or 2,7-dibenzosilole and acenaphtho[1,2-b]thieno[3,4-e]pyrazine. After the synthesis of these new copolymers, we have characterized the materials by UV-vis, DSC, and XRD to determine the degree of organization. Afterward, we have fabricated and investigated field-effect transistors and photovoltaic cells from these polymers. The optimization of the thin film by thermal treatment have led to a field-effect mobility of 0.04 cm2/(V.s) and power conversion efficiency of 0.44%.
Silicon Based Inorganic/Organic Hybrid Materials for Deep Blue PHOLEDs
Authors: Kwon Soonnam , Wee Kyung Ryang , Kang Sang Ook
Published: August 2010

Deep blue PHOLED was achieved in the simple device structure of ITO/SiTPA/SiCBP: FIr6 5 wt%/SiTAZ/Liq/Al, where active layers were silicon based inorganic/organic hybrid materials of the types, SiTPA, SiCBP, and SiTAZ for HTL, EML host, and ETL respectively. Silicon incorporation into organic framework not only provided necessary morphological stability, but also engaged enhanced charge transporting capability essential to achieve highly efficient deep blue PHOLEDs. As a result, high performance silicon based HTL, EML host, and ETL materials were developed, exhibiting high charge mobility in the range of 10−4 ∼ 10−3 cm2V−1s−1 and high triplet energy of 2.88 eV, 3.05 eV and 2.84 eV, respectively.

Even with the simple four layer device structure of PHOLEDs comprising silicon based active layers, maximum external quantum efficiency (EQE) of 17 % and CIE coordinates of (0.15, 0.22) were achieved. Moreover, an EQE of 15% was recorded at a luminance of 1000 cd m−1, which was the result of reduced efficiency roll-off due to the efficient confinement of FIr6 triplet energy by surrounding silicon based inorganic/organic hybrid materials developed in this work. Structures of inorganic/organic hybrid materials and their photo-physical properties as well as device physics for high performance deep blue PHOLEDs will be presented.
Long-Living Emitting Electrochemical Cells Based on Supramolecular π-π Interactions
Authors: Costa Rubén D. , Ortí Enrique , Graber Stefan , Neuburger Markus , Hausecroft Catherine E. , Constable Edwin C.
Published: August 2010

The complex [Ir(ppy)2(dpbpy)][PF6] (Hppy = 2-phenylpyridine, dpbpy = 6,6'-diphenyl-2,2'-bipyridine) has been prepared and evaluated as an electroluminescent component for light-emitting electrochemical cells (LECs). The complex exhibits two intramolecular face-to-face π-stacking interactions and long-lived LECs have been constructed; the device characteristics are not significantly improved in comparison to analogous LECs with 6-phenyl-2,2'-bipyridine with only one π-stacking interaction.
Misfit Strain Relaxation by Secondary Phase Formation in Multiferroic BiFeO3 Epitaxial Thin Films
Authors: Wang Xue , Zhu Yinlian , Ma Xiuliang , Wang Can , Lu Huibin
Published: August 2010

Microstructures of BiFeO3 (BFO) thin films epitaxially grown on SrRuO3 (SRO) buffered SrTiO3 (STO) (001) substrates by laser molecular beam epitaxy were investigated by means of transmission electron microscopy (TEM). The results showed that the films grown under the oxygen pressures of 1Pa and 0.3Pa, respectively, contain parasitic phase embedded in the BFO phase. The parasitic phase was revealed to be poor in Bi and rich in Fe by high-angle annular dark-field (HAADF) imaging and energy dispersive X-ray spectroscopy (EDS) compositional analysis. In combination with selected area electron diffraction patterns, the parasitic phase was determined to be α-Fe2O3. By lowering oxygen pressure, the density and the size of α-Fe2O3 phase increases whereas the regularity decreases. High resolution TEM images showed that approximately periodic misfit dislocations exist at the interface between the α-Fe2O3 phase and the BFO matrix, indicating that the α-Fe2O3 particles are semi-coherently embedded in the BFO films. Less misfit dislocations were detected at the interfaces between the BFO films and the SRO/STO substrates, implying that the misfit strains in the films may be fully relaxed by the formation of α-Fe2O3 phase.
Determination Factors of Strain-relaxed Complex Domain Structure observed in Thick Epitaxial pb(Zr,Ti)O3Films
Authors: Nakaki Hiroshi , Utsugi Satoru , Fujisawa Takashi , Nakajima Mitsumasa , Ehara Yoshitaka , Yamada Tomoaki , Morioka Hitoshi , Ifuku Toshihiro , Funakubo Hiroshi
Published: August 2010

Crystal structure change with the temperature was investigated for 3 m-thick (100)/(001)-oriented epitaxial PbTiO3 films grown on SrTiO3 substrates. Complex strain-relaxed domain structure labeled as Type III was observed and directly transformed to the cubic phase at about 490°C. This transition temperature and the lattice parameter (a and c- axes) change with the temperature well agreed with the reported data for the PbTiO3 powders. The volume fraction of the (001) orientations, Vc, was almost independent of the temperature up to the phase transition temperature. The tilting angles of the spots in XRD plan view were almost the same with the estimated ones from the lattice parameters and the Vc. This suggests that the angle of the domains identified by the domain structure in Type III. This structure is mainly determined by the tetragonality, (c/a ratio) and the Vc.
Development of Ferroelectric Data Storage Test System for High-Density and High-speed Read/Write
Authors: Hiranaga Yoshiomi , Tanaka Kenkou , Uda Tomoya , Kurihashi Yuichi , Kimoto Yasuhiro , Tochishita Hikari , Kadota Michio , Cho Yasuo
Published: August 2010

In this study, we have developed ferroelectric data storage test systems based on scanning nonlinear dielectric microscopy (SNDM) to conduct various experiments concerning read/write capability. Nanodomain formation on ferroelectric recording media was studied using the data storage test system. A nanodomain dot array was successfully written on a single-crystal LiTaO3 recording medium. The diameter of the written dot was as small as 7 nm. Epitaxial-thin-film LiTaO3 recording media were also developed. Nanodomain dots with the diameter of 25 nm were written on the thin-film recording medium. In addition, a non-contact probe-height control technique was adopted to solve the problem of tip abrasion using higher-order nonlinear dielectric response detection method. Finally, a hard-disk-drive (HDD)-type ferroelectric data storage test system was developed for conducting read/write tests under conditions close to those of actual operation. Capabilities of reading at the bit rate of 2 Mbps and writing at the bit rate of 20 Mbps were confirmed using the HDD-type data storage test system.
The Average Valence Electron Number: Is it a relevant parameter for Ni2MnGa Alloys?
Authors: Neumann Kristin , Elmashai Khaled , Hickel Tilmann , Neumann Klaus-Ulrich , Ouladdiaf Bachir , Ziebeck Kurt
Published: August 2010

The influence is investigated of the average valence electron number on the systematic changes of a Ni2MnGa based alloy series. The experimental investigation focuses on an isoelectronic alloy series Ni2Mnx(CrFe)1-x/2Ga for which the average valence electron number is unchanged for any value of x. Based on the changes of physical properties of alloys in this series compared to Ni2MnGa it is argued that local lattice distortions are more relevant for driving the change in alloy characteristics, such as the martensitic phase transition temperature or the ferromagnetic ordering temperature, than the band filling by valence electrons.
Purification and Functionalization of Diamond Nanopowders
Authors: Lim Jong-Kwan , Baek Jong-Beom
Published: August 2010

Purification of diamond nanopowder (DNP) was conducted in a less-destructive mild polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5). The wide-angle X-ray diffraction (XRD) showed that the intensity of the characteristic diamond d-spacing (111) at 2.07 Å from purified DNP (PDNP) was fairly increased compared to pristine DNP, indicating that significant amount of carbonaceous impurities were removed. Chemical modification of pristine DNP and PDNP with 4-ethylbenzoic acid was carried out to afford 4-ethylbenzoyl-functionalized DNP (EBA-g-DNP) and PDNP (EBA-g-PDNP). The morphologies of EBA-g-DNP and EBA-g-PDNP from scanning electron microscopy (SEM) were further affirmed the feasibility of chemical modification. The results suggested that the reaction condition was indeed viable for the one-pot purification and functionalization of DNP. The resultant functionalized DNP could be useful for nanoscale additives. Hence, EBA-g-DNP and EBA-g-PDNP was brominated by using N-bromosuccinimide (NBS). The resultant N-brominated DNP and PDNP could be used as initiator for the atom transfer radical polymerization (ATRP) to introduce many polymers onto the surface of functionalized DNP and PDNP.
Nanocoating on Carbon Nanofibers by Plasma Polymerization of Ethylene Gas
Authors: Hernández-Hernández Ernesto , Neira-Velázquez María Guadalupe , Ramos-de Valle Luis Francisco , Ponce Arturo , Sánchez-Anguiano María Guadalupe
Published: August 2010

Ethylene gas was used to modify the surface of carbon nanofibers (CNFs) by plasma polymerization. The modified CNFs were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, dispersion test in chloroform and high resolution transmission electron microscopy (HRTEM).

The results of dispersion test in chloroform showed that the plasma treatment promoted a stable dispersion of the treated nanofibers in the solvent. The FTIR results indicated that an organic polymer was deposited on the surface of the CNFs, and the Raman spectra showed evidence of the chemical interaction between the nanofibers and the polyethylene (PE) deposited by plasma. The presence of the thin polymer coating on the surface of CNFs was confirmed by HRTEM.
Microparticle filtration using carbon nanotubes and impedance characterisation for gold microelectrodes sensor system
Authors: Mathur Ashish , Hamad Eyad M , Mukhopadhyay Subhadeep , Sinha Roy Susanta , McLaughlin Jim A
Published: August 2010

Blood-cell-free serum is required for most clinical chemistry tests. At present bend micro channel and polymeric pillars are used in polymer based microfluidic devices (such as PMMA) for the blood filtration. In this study, we have fabricated carbon nanotube (CNT) pillars on silicon from 20-50 μm in diameter with ˜10 μm spacing and integrate them inside the microfluidic channel with a view of using these for blood plasma filtration from whole blood, with passive capillary flow. Our main objective is to design a novel sensor, comprising CNT arrays, to filter/control whole blood flow, with an integrated micro patterned gold electrode which will be sealed by bonding into microfluidics structures. We have characterized the microfluidic channel by measuring the meniscus movement profiles. Also gold inter-digitated electrodes (IDEs) were fabricated on glass and immobilized with an antibody. These IDEs were used as an impedance-based biosensor using label-free antigen – antibody interaction. At a fixed frequency, the IDEs gave a linear response across the range of concentrations of secondary antibodies investigated (0 to 500 μg/mL).
Analysis of Tunnel Junction Suitable for 4000 Suns in Tandem High Efficiency Solar Cell Structures
Authors: Jung Donggeun , Carlin Conrad Zachary , Hauser John R. , Bedair Salah M.
Published: August 2010

The road to achieve ultra high efficiency is through multi-junction solar cells operating at high solar concentrations, larger than 1000 suns. Critical to the success of this approach is the development of tunnel junctions (TJ) that serve as electrically low loss interconnections, yet are optically transparent, using high band gap semiconductor material systems. We have previously reported the fabrication of a TJ made of n+-InGaP/ p+-AlGaAs with a band gap about 1.9 eV using Se and C doping, respectively. This TJ structure has a peak current density of 88 A/cm2 allowing it to be implemented in a three junction cell structure at solar concentrations as high as 4000 suns (x4000). Almost all reported conversion efficiencies higher than 40% have used this tunnel junction. This very high peak current density is unexpected in a high band gap material system, which is good news for the multi junction solar community. This seems to be due to the fact that the InGaP/AlGaAs interface has a staggered band line up. We will present the effect of this band line up at the heterointerface and its effect on the width of the depletion region and the peak current density. We also compare the current result from this heterostructure junction with an artificial homojunction made of n+-AlGaAs/ p+-AlGaAs doped to the same levels as that of the heterojunction. Results from the homojunction showed that peak current density is about one half of that obtained from the heterojunction at the same doping levels. A reasonable match between experimental result and the model was obtained when a value of 150 meV was used for ΔEc, the conduction band discontinuity at the interface. Both experiment and theory predicted that at a current density of about 80 A/cm2 with only about a few tens of meV drop across the TJ. This will have a minimal effect on the overall efficiency of the tandem solar cell structure when used at high solar concentrations.
Raman and Rutherford Backscattering Characterization of Ti-implanted Si above the Mott Limit
Authors: Olea Ariza Javier , Pastor David , Mártil Ignacio , González-Díaz Germán , Ibáñez Jordi , Cuscó Ramón , Artús Luis
Published: August 2010

We have analyzed the degree of crystalline lattice recovery in samples implanted with Ti concentrations well above the Mott limit and subsequently Pulsed-Laser Melting (PLM) annealed by means of Raman spectroscopy and Rutherford Backscattering Spectroscopy (RBS). Since very recently, theoretical studies predicted Ti interstitial sites for the Intermediate Band (IB) formation, the knowledge of the Ti impurity lattice location after PLM annealing is an essential point that can be elucidated by means of RBS measurements. After PLM annealings, Raman and RBS measurements have shown a decrease in the lattice crystalline quality as implanted dose is increased, yielding a significantly improvement of the lattice quality at the highest energy density studied. The RBS channeling spectra show that after PLM annealings Ti impurities are mostly occupying interstitial lattice sites.
Strength of Multicrystalline Silicon Wafers for Various Surface Conditions
Authors: Rupnowski Przemyslaw , Sopori Bhushan , Armentrout Dan , Good Ethan
Published: August 2010

This study focuses on fracture properties of silicon wafers used by the photovoltaic (PV) industry as substrates for solar cells. In the first part, we numerically model three fixtures that are often used to test the strength of PV wafers. In the second part, we employ our previously developed model to predict strength of the wafers as a function of loading fixture and surface treatment. Surface treatment is simulated by removing damage from the wafer surface.
Evaluating Amorphization Around Micro-Cracks in PV Silicon
Authors: Kulshreshtha Prashant K. , Youssef Khaled M. , Rozgonyi George
Published: August 2010

Since the initiation and propagation of a micro-crack in a silicon wafer introduces local variations in stress, it is critical to the understanding of wafer breakage that accurate profiling of stress be performed in the vicinity of the micro-crack. In this study, nanoindentation has been used to investigate the stress-relaxation during crack initiation and propagation in material of particular interest to the photovoltaic (PV) industry. The low load (<1 mN) capability of a Hysitron Triboindenter® was used to accurately profile the extent of plastic deformation and resulting amorphization. Measurements were made on Si samples extracted from top, middle and bottom of a (100) oriented single crystal ingot to evaluate the impact of different carbon, oxygen and metallic impurity concentrations. A gradual but significant drop in hardness from 10.2 to 6.9 GPa occurred as indents were made closer to the micro-crack and was attributed to local amorphization. Electron back scattered diffraction (EBSD) and Raman spectroscopy confirmed the amorphization, respectively, at nano- and micro-scale.
Inherent Buffer-layer Formation on Chalcopyrite Absorbers
Authors: Pettenkofer Christian , Hofmann Andreas , Lehmann Carsten , Dombrowa Alexandra
Published: August 2010

We report on epitaxial growth of ZnO on polycrystalline and (112) orientated CuInS2 and CuInSe2 thin films. Step-by-step growth and investigation by photoelectron spectroscopy (PES) and low energy electron diffraction (LEED) provided information on the growth mode and the electronic structure of the ZnO-CuInS2-interface. During the initial growth no ZnO is deposited. Instead a monolayer of ZnS is formed by depletion the CuInS2 surface of excess sulfur. Thereafter, the ZnO growth starts on the ZnS buffer layer. The band alignment derived from PES shows that the ZnS buffer layer is thin enough to provide a beneficial band alignment for photovoltaic applications. CuInSe2 (112) samples showed a similar behaviour, but at the chosen deposition temperature of 450°C only ZnSe growth is detected. At lower temperatures ZnO growth on top of ZnSe is observed. XPEEM experiments show an inhomogeneous interface.
Lower Temperature Si Thin Films by Metal Induced Growth for Lower Cost Solar Cells
Authors: Mersich Peter T , Anderson Wayne A , Giese Rossman F
Published: August 2010

Metal induced growth (MIG) was used to form epitaxial thin films of microcrystalline Si (μc-Si). By substituting Al as the catalyst metal in place of the usual Ni, x-ray diffraction (XRD) confirmed that μc-Si was successfully grown at temperatures between 350-525°C. At 525°C, a preferred orientation of (220) Si was observed with additional (111) and (311) Si orientations, while a temperature of 350°C resulted in a shift in preferred orientation to (111) Si. The lower limit for Al thickness was found to be between 10-20 nm with little crystallization and a smooth surface observed at 10 nm with XRD and SEM, respectively. Electrical measurements on Schottky diodes revealed space-charge limited conduction (SCLC) with an exponential distribution of trap levels due to diffusion of Al atoms into the Si, which was supported by analysis with energy dispersive x-ray spectroscopy (EDX) near the film surface. By depositing a thin layer of Co on top of Al prior to sputtering, the films exhibited increased crystallinity and a more uniform surface likely due to increased confinement of Al atoms. Electrical measurements demonstrated a shift from SCLC to thermionic emission in resulting Schottky diodes.
Enabling High-Throughput, Low-Cost Manufacturing of OLED Display and Lighting Panels
Authors: Long Michael , Koppe Bruce E , Redden Neil P , Boroson Michael L , Hatwar Tukaram K , Hamer John W
Published: August 2010

Large-scale manufacturing of organic light-emitting diode (OLED) panels for lighting and display has been slowed by several manufacturing factors, prominent among which are low throughput due in part to the fine metal mask technology for patterning the red-, green-, and blue-light-emitting pixels and low materials utilization efficiency of the available vacuum deposition technology. To overcome these impediments to low-cost OLED manufacturing, Kodak developed a blanket white-emitting OLED architecture in combination with a pixilated color filter array to eliminate the need for fine metal masks and developed a vacuum deposition technology capable of high deposition rates and high materials utilization efficiency. These developments, taken together, allow much higher throughput and yield on fifth-generation and larger substrates that promise to enable low-cost manufacturing of OLED displays and lighting panels. This paper focuses on the deposition technology Kodak developed, a flash vaporization process that can deliver very high materials utilization efficiency at high deposition rates for small-molecule OLED materials without increasing material decomposition.
Mechanisms of Radiation Damage and Properties of Nuclear Materials
Authors: Lumpkin Gregory R. , Smith Kath , Whittle Karl , Thomas Bronwyn S. , Marks Nigel A.
Published: August 2010

Radiation damage effects in ceramics, e.g., nuclear waste forms, transmutation targets, and inert matrix fuels, may have important implications for the physical and chemical stability of these materials as the cumulative radiation dose increases over time. A key aspect of scientific research in this area is the ability to understand the fundamental damage mechanisms through the combination of experimental and atomistic modelling techniques. In this paper, we review some of the lessons learned from the significant body of data now available for pyrochlore-defect fluorite based materials, followed by an illustration of the advantages of working on simple compounds with well established interatomic potentials. We conclude the paper with a description of radiation damage processes in the LaxSr1-1.5xTiO3 defect perovskites, a system that includes phase transformations, short-range order effects, and complex defect behavior.
How to Simulate the Microstructure Induced by a Nuclear Reactor with an Ion Beam Facility : DART
Authors: Luneville Laurence , Simeone David , Baldinozzi Gianguido , Gosset Dominique , serruys yves
Published: August 2010

Even if the Binary Collision Approximation does not take into account relaxation processes at the end of the displacement cascade, the amount of displaced atoms calculated within this framework can be used to compare damages induced by different facilities like pressurized water reactors (PWR), fast breeder reactors (FBR), high temperature reactors (HTR) and ion beam facilities on a defined material. In this paper, a formalism is presented to evaluate the displacement cross-sections pointing out the effect of the anisotropy of nuclear reactions. From this formalism, the impact of fast neutrons (with a kinetic energy En superior to 1 MeV) is accurately described. This point allows calculating accurately the displacement per atom rates as well as primary and weighted recoil spectra. Such spectra provide useful information to select masses and energies of ions to perform realistic experiments in ion beam facilities.
Evaluation of Adhesive Strength of Oxide Layer on Carbon Steel at Elevated Temperatures
Authors: Satou Manabu
Published: August 2010

Adhesive strength of the oxidation layers on carbon steel was evaluated by means of a laser shock method, which uses a pulsed laser to generate shock wave. Oxidation for 200 hours in air created 10-micron-thick magnetite on carbon steel. Typical strength of the layer was evaluated to be about 50MPa at ambient temperature. The adhesive strength was varied from around one-tenth of yield stress to the ultimate tensile strength of the base materials. The adhesive strength of the oxide layer depended on test temperature. It is possible that the adhesive strength becomes an essential parameter for the evaluation of the protective layers.
Grain Boundary Characteristics Evaluation by Atomistic Investigation Methods
Authors: Kaji Yoshiyuki , Tsuru Tomohito , Shibutani Yoji
Published: August 2010

The grain boundary has been recognized for one of the major defect structures in determining the material strength. It is increasingly important to understand the individual characteristics of various types of grain boundaries due to the recent advances in material miniaturization technique.

In the present study three types of grain boundaries of coincidence site lattice (CSL), small angle (SA), and random types are considered as the representative example of grain boundaries. The grain boundary energies and atomic configurations of CSL are first evaluated by first-principle density functional theory (DFT) and the embedded atom method (EAM) calculations. SA and random grain boundaries are subsequently constructed by the same EAM and the fundamental characteristics are investigated by the discrete dislocation mechanics models and the Voronoi polyhedral computational geometric method. As the result, it is found that the local structures are well accorded with the previously reported high resolution-transmission electron microscope (HR-TEM) observations, and that stress distributions of CSL and SA grain boundaries are localized around the grain boundary core. The random grain boundary shows extremely heterogeneous core structures including a lot of pentagon-shaped Voronoi polyhedral resulting from the amorphous-like structure.
The Lifetime of Polar-Optical Modes in Semiconductors
Authors: Ridley Brian K , Dyson Angela
Published: August 2010

An enduring problem in the engineering of high-power semiconductor devices is how to mitigate the effect of heating. Heating means the proliferation of phonons, and phonons, interacting with electrons directly affect the electronic performance of the device. Nowhere is this more evident than the role of hot polar-optical phonons in reducing the drift velocity in the channel of an HFET and hence reducing its performance at high frequencies. The task of describing hot-phonon effects is complicated by the coupling to plasma modes. We present a theory of coupled plasmon-phonon modes in GaN, how they interact with electrons and how their lifetime becomes density-dependent. Raman scattering in bulk material shows a reduction of lifetime with increasing density and we offer an explanation for this in terms of the frequency dependence of the anharmonic decay mechanism. Hot-phonon effects, however, involve modes with wave-vectors beyond those probed by Raman scattering. By adopting a single-pole approximation for these modes we have obtained the lifetime dependence on wave vector, electron temperature and density.
Investigating Coherent Zone-Folded Acoustic Phonons in Si/SiGe Superlattices by Transient Thermoreflectance Technique
Authors: Michel Hélène , Pernot Gilles , Rampnoux Jean-Michel , Dilhaire Stefan , Grauby Stéphane , Ezzahri Younès , Shakouri Ali
Published: August 2010

In this paper, we present a systematic study of coherent phonons in Si/SiGe superlattices with two different periods. The superlattice periodicity affects the acoustic properties of the structure. Transient thermoreflectance (TTR) technique is used to perform picosecond ultrasonics experiments and then, investigate coherent zone-folded acoustic phonons in different Si/SiGe superlattice structures. Several classes of coherent phonons are produced in the superlattice, whose generation mechanisms are different: Brillouin oscillations, coherent longitudinal-acoustic phonon Bragg reflection and impulsive stimulated Raman scattering (ISRS).
Correlating Nanoparticle Dispersion to Surface Mechanical Properties of TiO2/Polymer Composites
Authors: Pang Yongyan , Watson Stephanie S. , Forster Aaron M. , Sung Lipiin
Published: August 2010

The objective of this study is to characterize the nanoparticle dispersion and to investigate its effect on the surface mechanical properties of nanoparticle-polymer systems. Two types of TiO2 nanoparticles were chosen to mix in two polymeric matrices: solvent-borne acrylic urethane (AU) and water-borne butyl-acrylic styrene latex (latex) coatings. Nanoparticle dispersion was characterized using laser scanning confocal microscopy. Overall, Particle A (PA, without surface treatment) dispersed better than Particle B (PB, organic treatment) in both systems. The AU-PA system exhibited the best dispersion of the four systems, however PB forms big clusters in both of the matrices. Surface mechanical properties, such as surface modulus at micron and sub-micron length scales were determined from depth sensing indentation equipped with a pyramidal tip or a conical tip. The surface mechanical properties were strongly affected by the dispersion of nanoparticle clusters, and a good correlation was found between dispersion of nanoparticle clusters near surface and the modulus-depth mapping using a pyramid tip.
Size Effect in the Shear-Coupled Migration of Grain Boundaries Pinned by Triple Junctions
Authors: Gil Sevillano Javier , Luque Aitor , Aldazabal Javier , Martinez-Esnaola José Manuel
Published: August 2010

This paper presents molecular dynamics simulations of shear-coupled migration of tilt boundaries pinned by triple junctions in a simple model structure of columnar grains of different sizes. Simulations are for copper at 300 K. The phenomenon is of interest as a possible explanation of the Hall-Petch relationship breakdown in nano-grained polycrystals deformed at high or moderate strain rate and low-temperature.
Mechanochemical Synthesis of Novel Sensor Materials
Authors: Sorescu Monica , Diamandescu Lucian , Tomescu Adelina
Published: August 2010

The xZnO-(1-x)alpha-Fe2O3 and xZrO2-(1-x)alpha-Fe2O3 nanoparticles systems have been obtained by mechanochemical activation for x=0.1, 0.3 and 0.5 and for ball milling times ranging from 2 to 24 hours. Structural and magnetic characteristics of the zinc and zirconium-doped hematite systems were investigated by X-ray diffraction (XRD), Mössbauer spectroscopy and conductivity measurements. Using the dual absorber method, the recoilless fraction was derived as function of ball milling time for each value of the molar concentration involved. As ZnO is not soluble in hematite in the bulk form, the present study clearly illustrates that the solubility limits of an immiscible system can be extended beyond the limits in the solid state by mechanochemical activation. Moreover, this synthetic route allowed us to reach nanometric particle dimensions, which makes these materials very important for gas sensing applications.
A Package for Fast FEM-based Simulation of X-ray Diffraction From Nano-structures
Authors: Wintersberger Eugen , Oswald Jay
Published: August 2010

In this work a novel package for the calculation of the diffracted intensity from nano-structures based on finite element simulations is presented. Besides a short introduction into the algorithm which we have developed two examples namely the diffraction from Si/SiGe systems with ripples and quantum dots with dislocations are shown.
Observation of Ultrafast Lattice Heating in thin Metal Films using Time-resolved Electron Diffraction
Authors: Ligges Manuel , Streubühr Carla , Brazda Thorsten , Posth Oliver , Hassel Christph , Dumpich Günter , Zhou Ping , von der Linde Dietrich
Published: August 2010

We show that time-resolved electron diffraction is capable of revealing the ultrafast lattice heating in thin metal films following excitation by a femtosecond laser pulse. The build-up of the lattice temperature leads to a reduction of the diffraction intensity of the various diffraction orders due to the Debye-Waller-effect. We also observed a reduction of the transmitted (000)-signal which exhibits the same temporal evolution as the diffraction signals.
Label-free Electrochemical Impedance Detection of Ovarian Cancer Markers CA-125 and CEA
Authors: Whited Allison M , Singh Kanwar V , Solanki Raj , Evans David R
Published: August 2010

CA-125 and carcinoembryonic antigen (CEA) are two biomarkers present in blood that can indicate the presence of ovarian cancer. They can also be used, both in conjunction with each other and independently, to determine the effectiveness of the treatment being meted for the disease. A label-free multiplexed interdigitated electrode array (IDEA) immunosensor was developed to detect both CA-125 and CEA in buffer solution at levels typically seen in patients with ovarian cancer . Electrochemical impedance spectroscopy was used to measure the increase in impedance when a binding event occurred between the target antigen and its specific antibody that was anchored to the surface of an interdigitated electrode array. CA-125 was detected in concentrations as low as 10units/mL and as high as 80units/mL. CEA was detected in concentrations as low as 1pg/mL and as high as 10μg/mL.
A Microfluidic Chip for Analysis of Mechanical Forces Generated During Cell Migration
Authors: Zheng Xiaoyu , Frohlich Else , Collignon Sean , Zhang Xin
Published: August 2010

Vascular smooth muscle cell migration is a microscopic in vivo process where specific cells crawl in order to partake in crucial physiological functions relating to embryonic development, wound healing, and tissue development. Abnormalities of cell migration result in pathologies such as tumor metastasis, angiogenesis, chronic inflammation, and various immune response dysfunctions. The mechanism behind cellular migration and the role of intracellular proteins in the instigation of cell directionality remains poorly understood without effective biomedical device available. The development of microfluidic biochips technologies enable detection, sample preparation and treatment on one single chip. We are reporting the design and fabrication of a novel microfluidic trip for guiding and quantifying cell migrations. The chip featured micropillar arrays imbedded in a multichannel microfluidic chip, where cell migration can be guided by utilizing the characteristics of laminar flow. Non-blending layers of fluid injected through the multi-channel device simulated a wounded edge across a monolayer of cells by limiting flow of trypsin, a serine protease, to half of the main channel, promoting cell migration in a desired direction. Control over cell directionality allows for the measurement and analysis of mechanical forces generated during cell migration in relation to migratory responses from intracellular protein inhibition. The micro-fluidic chip template was designed and manufactured using photolithography techniques. Polydimethylsiloxane (PDMS) served as the bulk material of the two compromising chip layers (channels and pillars), which were subsequently aligned and adhered to form the device. It was confirmed through both computer simulation and experimentation that the through optimized arrangement of the chip design, this device can effectively hold laminar flows of trypsin and cell media. Thus, this microfluidic device allows the user to simultaneously acquire force data during cell migration and observe migratory patterns to ultimately gain a better understanding of the underlying mechanisms of cell migration and directionality.
Hybrid Nanomaterial Scaffolds for Specific Biomedical Applications
Authors: Gadre Mandar , Yang Jianing , Zenhausern Frederic
Published: August 2010

Highly porous nanomaterials like aerogels, hybrid crosslinked aerogels (X-aerogels) and xerogels exhibit a broad range of tailorable properties such as the pore size, surface area, surface chemistry and mechanical strength. The versatile manufacturing route of sol-gel synthesis and various tunable properties makes aerogels and xerogels attractive candidates for biomedical applications including tissue engineering, sample collection applicators and engineered microenvironments for three-dimensional cell culture. The present study explores meso- and macroporous inorganic-organic hybrid aerogels prepared via sol-gel processing for two different applications, namely, as scaffolds for cell culture and as potential materials for sample collection applicators.
Magnetic properties characterization of functionalized iron oxide nanoparticles
Authors: Yuan Yuan , Borca-Tasciuc Diana-Andra
Published: August 2010

This paper uses complex magnetic susceptibility measurements to investigate the effects of different coatings on the susceptibility of iron oxide nanoparticles. The two coatings used in these measurements are aminosilane and carboxymethyl-dextran. Susceptibility measurements are carried out over a range of frequencies from 10 KHz to 1 MHz using a differential impedance method. The differential impedance measurement setup is validated by measuring the susceptibility of ferrofluids and comparing the results to values previously published in literature. The theoretical relaxation times based on Brownian and Neel mechanisms are used to predict the resonance frequency of imaginary part of complex susceptibility for iron oxide nanoparticles.
Adhesion Between Anti-EphA2 Antibody-Coated AFM Tips and Breast Cancer Cells
Authors: Paetzell Emily , Bogorad Andrew , Meng Juan , Soboyejo Winston oluwole
Published: August 2010

This paper presents the results of atomic force microscope (AFM) measurements of the adhesion force between MDA-MB-231 breast cancer cells and anti-EphA2 antibody-coated AFM tips. As a control, the adhesive interactions are measured between Hs578Bst normal breast cells and anti-EphA2 antibody-coated AFM tips. The measurements show conclusively that the adhesive forces to breast cancer cells are over five times greater than those to normal breast cells. The increase is attributed largely to the interactions between anti-EphA2 antibody and over-expressed EphA2 receptors that are revealed by the staining of receptor-ligand interactions. The implications of the results are discussed for the localized targeting and treatment of cancer with antibody-conjugated nanoparticles.
Role of Scaffold Architecture and Mechanical Properties of Electrospun Scaffolds in Cell Seeding
Authors: Wanasekara Nandula D. , Chen Ming , Chalivendra Vijaya B , Bhowmick Sankha
Published: August 2010

Seeding a layer of cells at specific depths within scaffolds is an important optimization parameter for bi-layer skin models. The work presented investigated the effect of fiber diameter and its mechanical property on the depth of cell seeding for electro-spun fiber scaffold. Polycaprolactone (PCL) is used to generate scaffolds that are submicron (400nm) to micron (1100nm) using electro-spinning. 3T3 fibroblasts were seeded on the electro-spun fiber scaffold mat of 50-70 microns thickness in this study. In order to investigate the effect of fiber diameter on cell migration, first, the electrospun fiber scaffold was studied for variation of mechanical properties as a function of fiber diameters. Atomic force microscopy (AFM) was used to investigate the Young’s modulus (E) values as a function of fiber diameter. It was identified that as the fiber diameter increases, the Young’s modulus values decreases considerably from 1.1GPa to 200MPa. The variation in E is correlated with cell seeding depth as a function of vacuum pressure. A higher E value led to a lower depth of cell seeding (closer to the surface) indicating that nanofibrous scaffolds offer larger resistance to cell movement compared to microfibrous scaffolds.
Nanoclay-reinforced Polyacrylamide Composite: Synthesis, Structural and Mechanical Characterization
Authors: Sun Yong , Huang Zaiwang , Li Xiaodong
Published: August 2010

A facile electrophoretic deposition method was successfully applied to achieve novel nanoclay-reinforced polyacrylamide nanocomposite thin films. A special curled architecture of the re-aggregated nanoclay-platelets was identified, providing a possible source for realizing the interlocking mechanism in the nanocomposites. The curled architecture could be the result from strain releasing when the thin films were peeled off from the substrates. Through micro-/nano-indentation and in situ observation of the deformation during tensile test with an atomic force microscope (AFM), the localized deformation mechanism of the synthesized materials was investigated in further details. The results implied that a localized crack diversion mechanism worked in the synthesized nanocomposite thin films, which resembled its nature counterpart-nacre. The deformation behavior and fracture mechanism were discussed with reference to lamellar structure, interfacial strength between the nanoclays and the polyacrylamide matrix, and nanoclay agglomeration.
Biomimetic Spinning of Recombinant Silk Proteins
Authors: Keerl David , Hardy John George , Scheibel Thomas
Published: August 2010

In the past, we have successfully designed and produced a variety of engineered spider silk-like proteins (eADF3 and eADF4) based upon the primary sequence of the natural dragline proteins ADF3 and ADF4 from the spider Araneus diadematus [1]. Genetically engineered spider silk proteins can be modified at the molecular level to optimize the biochemical and mechanical properties of the final product. Although engineered spider silk proteins can be processed into fibers using different spinning methods, our group is interested in the technical realization of a biomimetic approach.
Here, we present an overview over our biomimetic fiber production process.
Properties of Electrospinning Jets
Authors: Reneker Darrell H , Xin Yu , Lee Hyungjin , Lin Yinan , Liu Kaiyi , Zhong Zhenxin
Published: August 2010

Measurement of elongational stresses, stereographic images of jet paths, innovative collection of fluid jets, and utilization of elongational flow for assembly or disassembly of particulate structures, the electron microscopic views inside nanofibers, and the morphological and crystallographic changes that occur during heating of the metastable electrospun fibers illuminate the growing versatility of the electrospinning process.
Electrospun Polyacrylonitrile Nanocomposite Fibers Reinforced with Magnetic Nanoparticles
Authors: Zhang Di , Wei Suying , Guo Zhanhu
Published: August 2010

The manufacturing of magnetic PAN/Fe3O4 nanocomposite fibers is explored by an electrospinning process. The nanocomposite fibers were characterized by scanning electron microscopy (SEM). The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried as-received nanoparticles.