bluuebunny/crossref_metadata_2025_split huggingface dataset:
Device Processing for GaN High Power Electronics
Authors: Pearton S.J. , Cao X.A. , Cho H. , Lee K.P. , Monier C. , Ren F. , Dang G. , Zhang A.P. , Johnson W. , LaRoche J.R. , Gila B.P. , Abernathy C.R. , Shul R.J. , Baca A.G. , Han J. , Chyi J.-I. , Hove J.M. Van 
Published: April 2011

ABSTRACTRecent advances in developing process modules for GaN power devices are reviewed. These processes include damage removal in dry etched n- and p-GaN, implant doping and isolation, novel gate dielectrics, improved Schottky and ohmic contacts and deep via etching of SiC for hybrid GaN/SiC structures.
Characterization of n-type layer by S+ ion implantation in 4H-SiC
Authors: Tanaka Yasunori , Kobayashi Naoto , Okumura Hajime , Yoshida Sadafumi , Hasegawa Masataka , Ogura Masahiko , Tanoue Hisao 
Published: April 2011

ABSTRACTWe investigated the optical, electrical and structural properties of the layer which was implanted with sulfur ion(S+) in 4H-SiC. By using the high temperature ion implantation technique more less residual defects were observed compared with the room temperature ion implantation by Rutherford backscattering spectrometry and channeling(RBS-channeling). After annealing at 1700°C there was no significant difference between the implanted sample and virgin sample in crystallinity within the detection limit of RBS-channeling. From the result of low temperature photoluminescence(LTPL) we could see the photoluminescences, so-called D1 and D2center, originating in the defects formed by ion implantation and post-annealing(∼1700°C) processes and confirmed that their intensities decreased with the increasing of the total dose of S+. The result of Hall effect measurement suggested that the conduction type of S+-implanted layer is n-type and their activation energies were 275meV and 410meV by the fitting of neutrality equation assuming the two activation energies for the hexagonal and cubic lattice sites in 4H-SiC.
Effects of Electrode Spacing on Reactive Ion Etching of 4H-SiC
Authors: Bonds Janna R. , Carter Geoff E. , Casady Jeffrey B. , Scofield James D. 
Published: April 2011

ABSTRACT4H-SiC was selectively etched in a Reactive Ion Etch (RIE) system using a nickel mask. The power, pressure, and electrode spacing were varied within a RF generated SF6:O2 (1:2) plasma. Peak etch rates of up to 2600 Aring;/min. were obtained at a pressure of 350 mT, power of 90 W (2 W/cm2), and electrode spacing of 3.180 cm. Etches were all residue-free, although power levels above 60 W (1.36 W/cm2) resulted in the SiC surface being roughened, which limited smooth surface etch capability to 2000 Aring;/min. When comparing electrode spacing from 3.180 cm to 1.270 cm, the 3.180 cm spacing was found to have the highest etch rate at pressures ranging from 250 mT to 500 mT.
Thin Na0.5K0.5NbO3 Films for Varactor Applications
Authors: Cho C.-R. , Koh J.-H. , Grishin A. , Abadei S. , Petrov P. , Gevorgian S. 
Published: April 2011

AbstractSingle phase Na0.5K0.5NbO3 (NKN) thin films have been pulsed laser deposited on SiO2/Si(C-01) wafers and LaAlO3(001) and MgO(001) single crystals. Radio frequency (up to 1 MHz) and microwave (up to 50 GHz) dielectric spectroscopy studies have been carried out to characterize thin NKN films for electrically tunable microwave device applications. Films on single crystal oxide substrates showed tunabilities as high as 30-40 % at 40 V bias and dissipation factor of 0.01-0.02 at 1 MHz. The films on Si substrates showed low dielectric losses of < 0.01, and low leakage currents. Dielectric properties of ferroelectric films on Si substrates at low frequencies are greatly influenced by the depletion capacitance and the resistance inserted by semiconductor substrate. Microwave frequency measurements for NKN film on Si wafers yield more than 10 % tunability at 50 GHz and loss tan σ <0.1 at 10 GHz.
Simulation of a Simplified Design for a Nanoscale Metal-Oxide Field Effect Transistor
Authors: Newns D. M. , Donath W. M. , Pattnaik P.C. 
Published: April 2011

AbstractWe describe simulations on a simplified design for a metal-oxide nanoscale Field Effect Transistor (FET). The device features an oxide channel with a high dielectric constant ferroelectric as the gate insulator. In the present model, the gate and source/drain electrodes are unconventionally placed on opposite sides of the channel. Simulations are quantum mechanical and are based on a simplified transport model. Results on a 10 nm. channel device show adequate conductance and ON/OFF ratio, while simulation of a ring oscillator yields an estimated device switching time of 300 fs..
The Effects of Mg Doping on the Materials and Dielectric Properties of Ba1-xSrxTiO3 Thin Films
Authors: Cole M.W. , Joshi P.C. , Pfeffer R.L , Hubbard C.W. , Ngo E. , Ervin M.H. , Wood M.C. 
Published: April 2011

AbstractWe have investigated the dielectric, insulating, structural, microstructural, interfacial, and surface morphological properties of Ba0.60Sr0.40TiO3 thin films Mg doped from 0 to 20 mol%. A strong correlation was observed between the films structural, dielectric and insulating properties as a function of Mg doping. Non textured polycrystalline films with a dense microstructure and abrupt film--Pt electrode interface were obtained after annealing at 750°C for 30 min. Single phase solid solution films were achieved at Mg doping levels up to 5 mol%, while multiphased films were obtained for Mg doping levels of 20 mol%. Decreases in the films dielectric constant, dielectric loss, tunability and leakage current characteristics were paralleled by a reduction in grain size as a function of increasing Mg dopant concentration. Our results suggest that Mg doping serves to limit grain growth and is thereby responsible for lowering the dielectric constant from 450 to 205. It is suggested that Mg behaves as an acceptor-type and is responsible for the doped films low dielectric loss and good leakage current characteristics. Performance-property trade-offs advocates the 5 mol% Mg doped Ba0.60Sr0.40TiO3 film to be an excellent choice for tunable microwave device applications.
Fabrication of MgIn2O4 Thin Films With Low Resistivity on MgO (100) Surface by PLD Method
Authors: Noshiro R. , Ueda K. , Hosono H. , Kawazoe H. 
Published: April 2011

AbstractThin films of MgIn2O4 spinel, which is a recently discovered TCO material, were deposited on MgO (100) surface by PLD. The thin films were prepared under low oxygen partial pressure to enhance formation of oxygen vacancies, from which carrier electrons were generated. X-ray analyses and AFM observations suggest epitaxial growth of the grains with diameter of 100∼200nm. The grains showed strong orientations both along the normal of the thin film and in plane. Epitaxial growth of the spinel was also confirmed by high-resolution transmission electron microscopic observations. The lattice image of the interface region suggests formation of structural imperfections such as dislocations, grain boundaries and amorphous phase in significant fraction. Strong optical absorption due to electron carriers was detected in near infrared region. Very large Burnstein-Moss shift was observed in ultraviolet region, and the optical band gap was estimated to be 4.3eV. DC conductivity observed was 4.5×103Scm−1, which is the highest value reported for the material so far. Concentration and Hall mobility of carrier electrons were found to be 2.1×1021cm−3 and 14cm2V−1s−1, respectively.
Development and Implementation of New Volatile Cd and Zn Precursors for the Growth of Transparent Conducting Oxide Thin Films Via Mocvd
Authors: Babcock J.R. , Wang A. , Edleman N.L. , Benson D.D. , Metz A.W. , Metz M.V. , Marks T.J. 
Published: April 2011

AbstractFor the growth of thin zinc group metal oxide films [i.e. cadmium oxide (CdO), cadmium stannate (Cd2SnO4), and zinc oxide (ZnO)] via metal-organic chemical vapor deposition (MOCVD), volatile Cd and Zn precursor families are needed. Starting with Cd, β-ketoiminates of varying substitution were prepared to elucidate structure-property relationships. The nature of the ligand substituents strongly influences the melting point (liquid precursors are desired). Unlike conventional Cd β-diketonates, these complexes are monomeric as determined by x-ray crystallography. Despite these advantageous characteristics, attempts to grow CdO thin films in a cold-wall MOCVD reactor using two such derivatives were not successful. This class of Cd complex appears to decompose thermally with time-- a likely cause of the poor performance. Therefore, a new series of more thermally stable Cd precursors was sought. Using the chelating diamine N,N,N1,N1-tetramethylethylenediamine (TMEDA), monomeric β-diketonates were prepared. The molecular structure of Cd(hfa)2(TMEDA) (hfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) confirms the monomeric structural assignment. This series of Cd complexes is appreciably more volatile and sublime more cleanly than the aforementioned β-ketoiminates, as determined by vacuum thermogravimetric analysis (TGA). In addition to this advantageous characteristic, these complexes are easily prepared under ambient laboratory conditions from commercially available starting materials in a single step. Following the protocol established for Cd, a volatile series of Zn precursors was also prepared. For the Zn series, the melting point was effectively tuned through variation of both the β-diketonate and diamine ligands. The use of the Cd and Zn β-diketonate precursors in the successful growth of CdO and ZnO thin films, respectively, by MOCVD is also presented.
Evaluation of LSCO Electrodes for Sensor Protection Devices
Authors: Schwartz R. W. , Sebastian M. T. , Raymond M. V. 
Published: April 2011

AbstractWe have evaluated lanthanum strontium cobalt oxide (La0.5OSr0.50COOx; LSCO 50/50) as a candidate “transparent” electrode for use in an electrostatic shutter-based infrared sensor protection device. The device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 – 500 Δ/sq.). To meet these needs, the effects of post-deposition annealing on the resistivity and optical absorption characteristics of sputter deposited LSCO thin films were studied. The as-deposited films were characterized by an absorption coefficient of ∼ 12,500 cm1−1 and resistivities of ∼ 0.08 to 0.5 Δ-cm. With annealing at 800°C, the resistivity decreased to 350 νΔ-cm, while the absorption coefficient increased to ∼ 155,000 cm1−1. By using a post-deposition annealing step at 800°C and controlling film thickness, it appears that a standard LSCO 50/50 material may possess the requisite conductivity and optical transmission properties for this sensor protection device.
Preparation and Characterization of LiCoO2 and LiMg0.05Co0.95O2 Thin Films on Porous Ni/NiO Cathodes for MCFC by Complex Sol-Gel Process (CSGP)
Authors: Lada W. , Deptula A. , Sartowska B. , Olczak T. , Cimielewski A.G. , Carewska M. , Scaccia S. , Simonetti E. , Giorgi L. , Moreno A. 
Published: April 2011

AbstractThe major disadvantage of Ni/NiO cathodes for a Molten Carbonate Fuel Cells (MCFC) application is dissolution of NiO in K/Li electrolyte that significantly decreases the cell lifetime. Thin films of LiCoO2 or LiMg0.05Co0.9502 were prepared on a cathode body in order to protect them against dissolution. For preparation of starting sols the Complex Sol-Gel Process (CSGP) has been applied. These sols have been prepared by adding of LiOH to aq. acetates solution of Co 2+(Mg2+) with ascorbic acid and then by alkalizing them with aqueous ammonia to pH=8. The cathode plates of various dimensions (to several hundreds cm2) have been dipped in these sols and withdrawn at rate a 1.7 cm/s. Commercially sintered Ni plates were always initially oxidized by heating at various temperatures. Their microstructure and mechanical properties as a function of temperature were observed. Heat treatment should be carried out under the dead load of the ceramic plates in order to avoid their waving. The best non-folded plates were obtained by treating them for lh at 550°C. The covered substrates were calcined for lh at 650°C, using low heating ratel°C/min. The presence of LiCoO2 in a deposited coating has been proved by EDS patterns. The resultant film thicknesses were measured by scanning electron microscopy (SEM) on the fractured cross-sections; they ranged from 0.5 to 2νm and depended on sol concentration and viscosity. A 350 hundred hours test in molten carbonates, proved that the cathode bodies covered with LiCoO2 are completely prevented from dissolution of Ni in a molten K/Li electrolyte. Dissolution of LiCoO2 coating was not observed as well. After treatment in a molten electrolyte SEM observations did not show any changes in microstructures and morphology of the covered cathodes.
Numerical Simulation of Laser Induced Substrate Heating for Direct Write of Mesoscopic Integrated Conformal Electronics (MICE)
Authors: Lowry S. , Sheu J. C. , Stewart Robert , Parkhill Robert 
Published: April 2011

ABSTRACTA numerical tool is developed to simulate the optical and thermal interactions of selected lasers with precursors and substrates in support of the emerging technology for the direct write of Mesoscopic Integrated Conformal Electronics (MICE). The code couples the Discrete Ordinate Method (DOM) radiation model with the multi-physics computation fluid dynamics code CFD-ACE to predict the conductive and radiative heat transport in the processThis paper provides a brief overview of the numerical model. Selected simulations are presented including comparison with empirical data. The capabilities, limitations, and potential applications of the model with respect to MICE are discussed. Future model enhancements are proposed
Calculation of Hamaker Constants in Nonaqueous Fluid Media
Authors: Bell Nelson , Dimos Duane 
Published: April 2011

ABSTRACTCalculations of the Hamaker constants representing the van der Waals interactions between conductor, resistor and dielectric materials are performed using Lifshitz theory. The calculation of the parameters for the Ninham-Parsegian relationship for several non-aqueous liquids has been derived based on literature dielectric data. Discussion of the role of van der Waals forces in the dispersion of particles is given for understanding paste formulation. Experimental measurements of viscosity are presented to show the role of dispersant truncation of attractive van der Waals forces
Ink Jet Deposition of Ceramic Suspensions: Modeling and Experiments of Droplet Formation
Authors: Reis N. , Derby B. 
Published: April 2011

AbstractWe have successfully printed green ceramic objects from slurries of Al2O3 dispersed in paraffin wax using a commercial ink-jet printer developed for pattern making (Sanders Prototype MM6PRO). Concentrated suspensions are generally more viscous than the fluids normally passed through ink jet heads. This may alter the response of the printing system to its process parameters, e.g. driving voltage and frequency. We have explored the influence of fluid properties on the ink jet behaviour using Computational Fluid Dynamics (CFD) modelling and a parallel experimental study to determine the optimum printing conditions for particulate suspensions.
Rapid Prototyping of Patterned Multifunctional Nanostructures
Authors: Fan Hongyou , Laópez Gabriel P. , Brinker C. Jeffrey 
Published: April 2011

AbstractThe ability to engineer ordered arrays of objects on multiple length scales has potential for applications such as microelectronics, sensors, wave guides, and photonic lattices with tunable band gaps. Since the invention of surfactant templated mesoporous sieves in 1992, great progress has been made in controlling different mesophases in the form of powders, particles, fibers, and films. To date, although there have been several reports of patterned mesostructures, materials prepared have been limited to metal oxides with no specific functionality. For many of the envisioned applications of hierarchical materials in micro-systems, sensors, waveguides, photonics, and electronics, it is necessary to define both form and function on several length scales. In addition, the patterning strategies utilized so far require hours or even days for completion. Such slow processes are inherently difficult to implement in commercial environments. We present a series of new methods of producing patterns within seconds. Combining sol-gel chemistry, Evaporation-Induced Self-Assembly (EISA), and rapid prototyping techniques like pen lithography, ink-jet printing, and dip-coating on micro-contact printed substrates, we form hierarchically organized silica structures that exhibit order and function on multiple scales: on the molecular scale, functional organic moieties are positioned on pore surfaces, on the mesoscale, mono-sized pores are organized into 1-, 2-, or 3-dimensional networks, providing size-selective accessibility from the gas or liquid phase, and on the macroscale, 2-dimensional arrays and fluidic or photonic systems may be defined. These rapid patterning techniques establish for the first time a link between computer-aided design and rapid processing of self-assembled nanostructures.
Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials
Authors: Venkataraman N. , Rangarajan S. , Harper B. , Matthewson M.J. , Safari A. , Danforth S.C. 
Published: April 2011

AbstractFused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the feedstock material. The filament acts as both the piston driving the extrusion process and the feedstock material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the feedstock viscosity control the buckling behavior of the filament material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of KE). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.
Refrigerative Stereolithography Using Sol-Gel Transformable Photopolymer Resin and Direct Masking
Authors: Murakami T. , Kamimura A. , Nakajima N. 
Published: April 2011

AbstractThe authors have been studying a new fabrication method termed “refrigerative stereolithography” which uses a gel resin layer instead of a liquid layer as in conventional stereolithography. This paper proposes the “direct masking method” in which a masking pattern is drawn to block direct light exposure to the surface of the gel resin layer. With such masks, we can avoid surplus growth only in the regions where it is unnecessary to improve height direction accuracy and resolution. Also, we can solidify the required section shape selectively using the masks and a lamp instead of laser scan patterns. The effectiveness of refrigerative stereolithography with the direct masking method is discussed and confirmed by some experimental results.
Formation of Nano-Sized Crystals During Plastic Deformation in Amorphous Alloys
Authors: Ogura A. , Sato M. , Tarumi R. , Shimojo M. , Takashima K. , Higo Y. 
Published: April 2011

ABSTRACTMicrostructural change in deformation bands was observed in a Ni-P amorphous alloy using transmission electron microscopy (TEM). Bending strain was applied to a micro-sized cantilever beam specimen. A TEM specimen was prepared from the micro-sized specimen with keeping the information on the relationship between the deformed direction and the specimen orientation. TEM observation in deformation bands revealed that plastic deformation induces the precipitation of nanocrystalline Ni particles. An orientation relationship between deformation direction and crystal orientation was obtained, that is, a (111) plane of all crystalline particles are parallel to the side surface of the specimen.
Cyclic Deformation and Fatigue Properties of Ultrafine Grain Size Materials: Current Status and Some Criteria for Improvement of the Fatigue Resistance
Authors: Mughrabi Haël , Höppel Heinz Werner 
Published: April 2011

ABSTRACTIn this review, some general conclusions based on studies performed to date on fatigued materials of ultrafine grain (UFG) size produced by equal channel angular pressing (ECAP) are drawn, and open issues of current interest are defined. Important aspects addressed include the apparent discrepancy between improved fatigue strengths in Wöhler (S-N) plots as opposed to inferior fatigue strengths in Manson-Coffin plots, the clarification of the microstructural mechanisms of severe cyclic softening in conjunction with dynamic (local) grain/subgrain coarsening and damaging large-scale catastrophic shear banding. The important roles of the cyclic slip mode, the friction stress, the crystal structure and the temperature of cyclic deformation with respect to stable cyclic deformation behaviour are emphasized. Based on such considerations, criteria are formulated that must be observed, when designing ECAP-processed UFG-materials of superior fatigue strength.
Simulation of Positron Characteristics in Nanocryartalline Materials
Authors: Kuriplach Jan , Petegem Steven Van , segers Danny , Dauwe Charles , Hou Marc , Zhrukin Eugenij E. , Swygenhoven Helena Van , Morales Alvaro L. 
Published: April 2011

ABSTRACTThe theoretical calculations of the position response to different types of defects can be very helpful in order to interpret properly positron measurements. In this contribution a new computational technique to determine position properties in nanocrystalline materials is presented. In such calculations we employ the realistic models of n-materials obtained using molecular dynamics. The new technique is based on the so-called atomic superposition method where atomic densities are superimposed in a selected region of the model (virtual) sample to approxiamte the electron density of the system. We study the virtual samples of n-Cu, n-NiAl, and n-Ni3Al, for which we calculate position lifetime and position binding energies corresponding to defects located in selected regions of the samples. The regions of interest for position calculations comprise grain boundaries inculding triple points, nano-voids, and bulk-like regions.