bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrostatic Pressure Studies of GaN/AlGaN/GaN Heterostructure Devices with Varying AlGaN Thickness and Composition
Authors: Steinke Isaiah , Kauser M. Z. , Ruden P. Paul , Ni Xianfeng , Morkoc Hadis , Son Kyung-ah 
Published: April 2011

AbstractGaN-based heterostructure devices are of interest for pressure and stress sensing applications due to their potential for use at high temperatures and in caustic environments. We have grown n-GaN/u-AlGaN/n-GaN heterostructure devices on sapphire substrates by organometallic vapor phase epitaxy (OMVPE) using the epitaxial layer overgrowth (ELO) method. The devices were fabricated with varying AlGaN layer thickness and composition. Current-voltage (I-V) characteristics were obtained to characterize the performance of these devices under hydrostatic pressures up to 500 MPa. For a fixed bias, the current was observed to decrease in magnitude with increasing hydrostatic pressure for all devices tested. The current modulation is attributed to piezoelectric effects. Specifically, the polarization charge densities at both GaN/AlGaN interfaces are sensitive to changes in the hydrostatic pressure, and these charges affect the shape of the potential barrier and the current. Changes in the AlGaN layer thickness and composition modify the interfacial polarization, with thicker AlGaN layers and higher Al content increasing the effect of pressure on the observed I-V characteristics. The decreases in current magnitude with increasing pressure are linear over the pressure range tested. In order to quantify the performance of these devices, we calculate a pressure gauge factor based on a normalized change in current divided by the change in pressure. Values obtained range from 0.1–1.0 GPa−1, consistent with our previously published results for a single device. In addition, the turn-on voltages under both forward and reverse bias conditions are observed to increase with increasing AlGaN layer thickness and composition, a result that agrees with our device model. These turn-on voltages are governed by different mechanisms in the forward and reverse bias directions. Under forward bias, the mechanism is a transition from a thermionic to a tunneling process. However, under reverse bias, the turn-on occurs when the total electric field changes sign in the AlGaN layer.
Radiation-Induced Deep-Level Traps in CCD Image Sensors
Authors: Tivarus Cristian , McColgin William C. 
Published: April 2011

AbstractDark current spectroscopy (DCS) is used to study deep level traps corresponding to the bright pixels that form the histogram “tails” of irradiated charge-coupled devices (CCD). We found four distinct traps, among which the double vacancy (V2) and the vacancy-phosphorous (VP) have the highest concentrations and generation rates. We show that DCS can be used to examine the annealing mechanisms of silicon defects to concentrations as low as 5 × 107 cm−3.
Electronic Structure of Si/InAs Composite Channels
Authors: Prada Marta , Kharche Neerav , Klimeck Gerhard 
Published: April 2011

AbstractElectronic structure calculations on composite channels, consisting of indium arsenide grown on the technologically relevant (001), (011) and (112)-orientated silicon surfaces are reported. The calculations are performed with NEMO 3-D, where atoms are represented explicitly in the sp3d5s* tight-binding model. The Valence Force Field (VFF) method is employed to minimize the strain. NEMO 3-D enables the calculation of localized states in the quantum well (QW) and their dispersion in the quantum well plane. From this dispersion, the bandgap, its direct or indirect in character, and the associated effective masses of the valence and conduction band can be determined. Such composite bandstructure calculations are demonstrated here for the first time. The numerical results presented here can then be included in empirical device models to estimate device performance. Pure InAs QWs create a direct bandgap material, with a relatively small gap and effective masses of about one order of magnitude smaller than for pure Si QW of equivalent thickness. Si, on the other hand, has a larger bandgap, superior thermal and mechanical properties, and a heavily invested industry. Thus heteroepitaxy of both components is expected to yield a highly optimized overall system. For samples grown along the (001) direction, Si is a direct bandgap material, and deposition of an InAs 3nm layer reduces substantially the hole effective mass and slightly the electronic mass, decreasing the magnitude of the gap. Along the (011) and (112)-growth direction, Si QWs are indirect bandgap material, and deposition of a few InAs layers suffies to make the new material a direct-bandgap heterostructure, decreasing significantly the electronic effective mass. (011) and (112) are the experimentally most relevant growth directions since they prevent heterointerface dipoles.
Comparative Study of Electronic Properties of Point Defects in Monoclinic Hafnium Dioxide
Authors: Cuny Valerie , Richard Nicolas 
Published: April 2011

AbstractContinuous downscaling of transistor leads silicon dioxide constituting the gate in typical metal oxide semiconductor field effect (MOSFET) to its limits. One possibility is to replace SiO2 by a material of higher dielectric constant (high-k). Hafnium dioxide seems to be the most promising one. However, high-k transistor performances are often affected by the presence of defects creating charge traps or diffusion centers. In this paper, using a pseudopotential plane wave code in the density-functional total theory framework, we calculate in a monoclinic HfO2 supercell the structure, formation and ionization energies, electron affinities of intrinsic defects (oxygen vacancy and interstitial, and hafnium vacancy). We consider different charge states of these defects. The positions of defect levels with respect to the bottom of silicon conduction band are determined. Our results will be discussed and compared to literature data.
The Electrical Characterization of Molecular-Beam-Deposited LaAlO3 on GaAs and its Annealing Effects
Authors: Choi Donghun , Warusawithana Maitri , Chui Chi On , Chen Joseph , Tsai Wilman , Schlom Darrell G. , Harris James S. 
Published: April 2011

AbstractThe electrical properties of Al/LaAlO3/GaAs metal-oxide-semiconductor capacitors were investigated. A thick arsenic (As2) capping layer was used to protect the GaAs from oxidation and contamination during the air exposure that occurred between the deposition of the GaAs and LaAlO3 layers in different molecular-beam epitaxy systems. Amorphous LaAlO3 was deposited on c(4×4)- and (2×4)-reconstructed (100) GaAs surfaces. Post dielectric deposition annealing was found to improve the capacitance-voltage (C-V) characteristics by eliminating frequency dispersion in the depletion and weak inversion regimes and diminished the bi-directional C-V hysteresis to 210 mV. Reasonably low gate leakage current was maintained after annealing.
Atomic-scale Characterization of HF-treated 4H-SiC(0001)1×1 Surfaces by Scanning Tunneling Microscopy
Authors: Arima Kenta , Hara Hideyuki , Sano Yasuhisa , Yagi Keita , Okamoto Ryota , Murata Junji , Mimura Hidekazu , Yamauchi Kazuto 
Published: April 2011

AbstractScanning tunneling microscopy (STM) observations are performed on 4H-SiC(0001) surfaces after wet-chemical preparation steps including HF treatments.1×1 structures are formed on a terrace together with other local structures. Their atomic images are investigated in conjunction with low-energy electron diffraction and electron spectroscopy for chemical analysis. It is suggested that each bright dot forming the 1×1 phase corresponds to an OH-terminated Si atom.
Effects of Annealing on Structural and Magnetic Properties of Cobalt Implanted TiO2 Thin Films
Authors: Luk W. Y. , Li Q. , Wong S. P. , Ho H. P. , Ke N. , Lindner J. K. N. 
Published: April 2011

AbstractSince the observation of room-temperature ferromagnetism (RTFM) in Co-doped anatase TiO2 [1], there have been many reports on the study of the magnetic properties of Co-doped TiO2 prepared by various methods with diversified results. The origin of the RTFM in these systems is still a topic of controversy today. In this work, TiO2 thin films were prepared by RF sputtering onto thermally grown oxide layers on Si substrates. Cobalt implantation was performed using a metal vapor vacuum arc (MEVVA) ion source to various doses ranging from 3×1015 cm-2 to 4×1016 cm-2. Post-implantation annealing was performed in a vacuum chamber at various temperatures ranging from 400°C to 700°C for 2 hours and 4 hours. Characterization of these films as-implanted and after thermal annealing under various conditions was performed using Rutherford backscattering spectrometry, energy filtered and high-resolution transmission electron microscopy, x-ray diffractometry, x-ray photoelectron spectroscopy, and vibrating sample magnetometry. The dependence of the magnetic properties on the implantation and annealing conditions were studied in detail. Clear RTFM properties were observed. The saturation magnetic moment per implanted Co atom (MS) seems to increase with increasing dose within the implantation dose range in this study. At a fixed dose, the MS value also shows a generally increasing trend with increasing annealing temperature and annealing time. Quite a number of samples showed MS values exceeding the bulk Co value of 1.69 ìB/Co significantly and the maximum MS value observed is about 3.16 µB/Co. Such high MS values indicate that the RTFM must not come from Co clusters alone. Possible origins of the RTFM properties will be discussed in conjunction with the structural properties.
Functionalizingλ-AlOOH Surface with Silanol -- an Ab-initio Study
Authors: Lehtinen Petri , Grundmeier Guido , Blumenau Alexander 
Published: April 2011

AbstractOn HDG-steel, zinc coatings are used for corrosion protection. Part of that coating is composed of aluminum and this leads to the creation of aluminum oxide film on the coating with thicknesses of 2-3 nanometers. This layer is an amorphous boehmite film.Boehmite, or λ-AlOOH, has several application areas, but for us the interesting ones are related to an area where the surface is functionalized, for example in a way that the organic and inorganic films can be “glued” together. A good candidate for the interface is the silanol molecule. The idea is that the OH-groups of the molecule attach on the inorganic film and the methyl groups on the organic film and hence promote adhesion between the two.We present theoretical ab-initio results of adsorption of water and silanol molecules on the λ AlOOH (0001)-surface. Since the experimental adsorption of the silanol on the boehmite surface is done in water environment, the adsorption process is therefore a competing process. We will present some result of adsorption of silanol in the presence of water molecules to get an insight into this process.
Sm-doped YBCO Coated Conductor on the IBAD MgO Template Fabricated by MOD Process
Authors: Shin Geo-Myung , Ko Rock-Kil , Song Kyu-Jung , Yoo Jae-Moo , Park Chan , Moon Seung-Hyun , Yoo Sang-Im 
Published: April 2011

AbstractMetal organic deposition (MOD) is one of the attractive processes for coated conductor applications because it is a non-vacuum cost-effective process. Many research groups have successfully fabricated high-JC YBCO coated conductor on the RABiTS and IBAD-YSZ or GZO template with the MOD process. Reports on MOD-processed YBCO coated conductors prepared on the IBAD-MgO template, however, are hardly found. The precursor solution was coated on the CeO2 capped IBAD-MgO template using the slot-die coating method, calcined at a temperature of 550oC, and fired at high temperatures for 2 h 30 min in a reduced oxygen atmosphere. Optimal processing resulted in YBCO coated conductors exhibiting JC value of 0.75 MA/cm2 at 77 K in self-field. The JC values of YBCO coated conductors were found very sensitive to their microstructure, critical temperature, and in-plane texture.
Flux Pinning Enhancement of YBCO Films by Y and Ba Site Doping at Minute Concentrations
Authors: Kell Joseph W. , Barnes Paul N. 
Published: April 2011

AbstractYBa2Cu3O7-x (Y123) superconducting thin films can maintain high critical current densities in applied magnetic fields up to a few Tesla at 77 K. Even so, this does not preclude the intentional addition of alternate flux pinning centers in the Y123 films to further optimize their in-field Jc. Unfortunately, many methods to incorporate flux pinning centers into Y123 thin films introduce additional steps and/or re-optimization of the deposition parameters for a given addition. Identifying potential additions that can optimize the performance of YBCO films without changing the deposition conditions would be ideal. The work presented here is an extension of earlier work and demonstrates new dopants and possibilities for introducing pinning centers by the route of minute doping or nanodoping. Preliminary results of a study to determine if minute doping can be performed with smaller lanthanide atoms (Tm, Lu), non-lanthanide atoms (Sc) and Ba-site substitution (Sr) are presented. All samples were deposited under identical conditions as pure YBCO. The new dopants will be discussed in addition to those previously presented (Tb, Pr, Ce, Nd, and La). Critical current density data will be presented for 65 K and 77 K in fields up to 9T in addition to new structural data obtained by cross-sectional TEM.
High Resolution Electron Beam Lithographic Deposition of Metal and Metal Oxide Films from Metal Complexes
Authors: Zhang Xin , Hill Ross H. 
Published: April 2011

ABSTRACTIn this paper, a method of direct electron beam lithographic deposition of metal and metal oxide films is demonstrated using metal organic complexes. In this method, a solution of a metal complex is used to spin coat a substrate to obtain a precursor film. The precursor film is then directly patterned by electron beam writing. A solvent is then used to develop the latent image. Using examples of titanium, tantalum, zirconium, and gold, we illustrate patterning of metal and metal oxide films and both positive and negative deposition. The feature size demonstrated is as low as 14 nm while the demonstrated aspect ratio is as high as 11.
Using Tubular Millifluidics as a Versatile Tool Box for The Generation of New Complex Architectures: Some Integrative Chemistry Synthetic Pathways
Authors: HANY Cindy , TACHIBANA Masatoshi , ENGL Wilfried , PANIZZA Pascal , BACKOV Ré;nal 
Published: April 2011

AbstractWe present a continuous flow scheme to produce hierarchically organized large emulsions and particles with very good control over size, shape and internal structure. By assembling together elementary co-axial flow modules and integrating their corresponding functions, modular set-ups can be designed “on demand” to engineer complex architectures in characteristic sizes ranging from 50 micrometers up to a few mm. The high potentiality of this approach stems from the continuous production of drops and the ability to manipulate and functionalize each one independently “on line”. Its great versatility is limited only by the number of combinations possible using the modular tool box and one's imagination. We illustrate this through the encapsulation of droplets or solid particles of various shapes, composition and size,in liquid or solidified drops as well as the formation of large organic or inorganic cylindrical particles.
Fabrication and Characterization of Electrowetting on the flexible substrate
Authors: Kim Jin-Young , Seo JungHo , Lee JungHwan , Kim KyuChae , Lim Hyun Woo , Park JinGoo , Jeon SungChae , Jin SeoungOh , Huh Young 
Published: April 2011

AbstractThis paper reports the fabrication of and characterization on EWOD(electrowetting-on-dielectric) devices on flexible substrates of interest to the flexible displays and devices. The EWOD devices were fabricated on PET (poly ethylene terephthalate) and PMMA (polymethylmethacrylate) substrates. Au and ITO(indium tin oxide) were used as electrode materials. The wet etching process was developed not to attack plastic flexible substrates. The photo resist was used as an insulator materials in EWOD devices due to the deformation of substrate when oxide layer was deposited on plastic substrate. As a hydrophobic layer, cytop was spin-coated on the photo resist. Wetting tests were done with DI water in air environment. In sessile droplet test, the contact angle of droplet changed from 116◦ to 80◦ under DC power. Threshold voltage was 20 Vdc. The droplet was oscillated under AC power because of the frequency. But the contact angle of droplet was began to change at 30Vac and decrease with the increase of AC power. In droplet transporting test, a droplet(0.2§¡) was started transporting at 20Vac and the transporting speed increased with the increase of AC power. But the droplet transporting was not occurred under DC power because of slower contact angle recovery rate under DC power.
Synthesis of Nickel-Coated Carbon Nanopaper Sheets by Pulse Laser Deposition
Authors: Gou Jihua , Blanco Roy , Zhao Zhongfu , Khan Aurangzeb , Appalla Aditya 
Published: April 2011

AbstractSurface coating of carbon nanotubes and carbon nanofibers can significantly improve their properties such as electrical, thermal, magnetic, acoustic, vibration, catalytic, optical properties. This paper presents a novel method to coat carbon nanotubes and carbon nanofibers by using as-prepared carbon nanopaper sheets. The carbon nanopaper sheet consisted of randomly oriented single-walled nanotubes and vapor grown carbon nanofibers, which formed into a highly uniform non-woven material. This flexible and lightweight material was coated with nickel by laser pulse deposition. The effects of deposition parameters on the morphology of the nanotubes and nanofibers will be studied using scanning electron microscopy. The electrical conductivities of carbon nanopaper sheets associated with deposition parameters will be characterized using four-point probe method. The deposition parameters will be optimized to achieve a highly conductive carbon nanopaper sheet.
Hierarchically Porous Oxides, Hybrids and Polymers via Sol-gel Accompanied by Phase Separation
Authors: Nakanishi Kazuki 
Published: April 2011

ABSTRACTIn various crosslinking systems containing metal oxides, organo-siloxane polymers and pure hydrocarbons, monolithic materials with hierarchical well-defined macropores and controlled mesopores have been synthesized. Synthetic progress in alkoxy-derived macroporous silica lead to the preparation of long-range ordered mesoporous skeletons in well-defined macroporous framework. Alkylene-bridged silicon alkoxides can also be prepared into similarly hierarchical porous structures with broadened variations in framework morphology. Macro-mesoporous alkoxy-derived pure titania and zirconia have been prepared using hydrochloric acid – mediated processes. Compared with those prepared from colloidal dispersions, alkoxy-derived macroporous titania exhibited much higher mechanical strength. Titania monolith is a promising candidate as a separation medium to discriminate phosphorylated compounds in a liquid chromatography mode. Pure alumina macroporous monolith has been first synthesized from aluminum salt using propylene glycol as a proton scavenger to thrust the solution pH from acidic into neutral conditions. Alumina-based complex oxides such as garnets and spinels can also be prepared in pure phases. Polymerization and phase separation in organic crosslinker system was also controlled to obtain well-defined co-continuous macro-frameworks instead of those composed of aggregated particles. These examples demonstrate the versatility of using phase-separation in gelling systems to obtain well-defined macroporous structures.
Low Temperature Deposition of Metal Oxide Thin Films in Supercritical Carbon Dioxide Using Metal-organic Precursors
Authors: Gougousi Theodosia , Chen Zhiying 
Published: April 2011

ABSTRACTA novel chemical route in thin film formation that includes the use of inorganic and organic peroxides and metal organic complexes soluble in supercritical carbon dioxide has been investigated for the deposition of alumina, titania and zirconia thin films at low temperatures (<150°C). The metal organic precursors used include: Al(acac)3, OTi(tmhd)2, and Zr(acac)4. Tert-butyl peroxide, and a 30% aqueous solution of hydrogen peroxide were used as oxidants. Depositions were carried out in a 25 ml hot wall reactor at pressures ranging from 2100 to 3900 psi at 80-140°C. The deposited thin films were investigated by using X-ray photoelectron spectroscopy (XPS) and transmission Fourier transform infrared spectroscopy (FTIR). XPS and FTIR results indicate the formation of metal oxides thin films with some bonded carbon. The deposition temperatures achieved in this process are substantially lower than those used in conventional vacuum deposition techniques making feasible the deposition on temperature sensitive substrates and organic materials required for the development of hybrid organic/inorganic devices. Processing at low temperatures in supercritical carbon dioxide may provide the basis for the development of an alternative, environmentally friendly, thin film deposition technique for the processing of nanostructures.
Evaluation of Cationic Biopolymers for the Design of Silica-coated Alginate Capsules
Authors: Bruyant Aurelie , Coradin Thibaud 
Published: April 2011

ABSTRACTLysozyme and chitosan were evaluated as cationic polymers for the design of silica-coated alginate capsules. No direct relationship was found between the strength of the bio-organic poly-electrolyte membrane and the stability of capsules after the silica coating, which depends mainly on the nature of poly-cation/silicate interactions.
Study of the Architecture of Inorganic-Organic Matrix in the Ventral Segmental Concretion of Porcellius Chilensis Nicolet, 1849 (Crustacea, Isopoda)
Authors: Pai Ranjith Krishna , Neira-Carrillo Andrónico , Fernandez Maria Soledad , Arias José Luis 
Published: April 2011

ABSTRACTMineralized biological concretions have attracted increasing interest because of their outstanding properties. The mineralized concretion of terrestrial isopods is an excellent model for acellular natural composite material. Before the molt terrestrial isopods resorb calcium from the posterior cuticle and store it in concretion within the cranial (head) and caudal (tail) ventral segments. This paper present for the first time an analysis of ultrastructural changes occurring in the caudal ventral segmental (CaVS) concretion of a terrestrial isopod Porcellius chilensis during their formation and degradation. The CaVS concretion of the woodlice Porcellius chilensis was analyzed with respect to their content of inorganic material. It was found that the concretion consists of amorphous calcium carbonate (ACC), and amorphous calcium phosphate (ACP), besides small amounts of water and an organic matrix. The CaVS concretion consists of structurally distinct stratum due to inhomogeneous solubility of ACC within the organic matrix that consists of calcareous knob with reticules elements. The organic matrix plays a role in the structural organization of the concretion and in the stabilization of ACC, which is unstable in vitro. We present an analysis of the distribution of minerals, elements, and organic matrix with in the CaVS concretion by using SEM, XRD, IR and EDS. The decalcification experiments exactly imitated the natural demineralization of the CaVS concretion of the Porcellius chilensis and it is thought that an inhomogeneous solubility of ACC and ACP within the CaVS concretion probably caused by variations in the stabilizing properties of matrix components.