bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of a Post-Emitter RTP on Bipolar NPN Beta Degradation Lifetime for 1.0 Micron & 0.8 Micron BICMOS Processes
Authors: Leitz W. E. , Modi G. , Parekh N. , Sabin E. , Taylor R. V.
Published: April 2011

Rapid Thermal Processing (RTP) has sometimes been used to increase bipolar NPN Beta (Hfe, or current gain) for a polysilicon emitter BICMOS process. It has been demonstrated that Beta may be increased by 20%, compared to normal non-RTP process values, by the addition of an RTP cycle after the final high temperature furnace step. In our work it was found that emitter-base reverse bias degrades Beta much more severely for a process which uses RTP, than for a non-RTP process. In this paper we will report on the electrical performance effects of RTP on a variety of process parameters. The reliability effects on NPN Beta degradation lifetime, and NMOS reliability effects will be discussed as well.
Microwave Melting of Ion-Conducting Glasses
Authors: Duval D. J. , Terjak M. J. E. , Risbud S. H. , Phillips B. L.
Published: April 2011

Glasses of the system AgI-Ag2O-(0.95B2O3:0.05SiO2) have been formed by microwave processing using a domestic multi-mode oven operating at 900 watts and 2.45 GHz. Microwave heating resulted in rapid melting times with homogeneity in the quenched glasses equivalent to or better than conventional melting at 730°C. The glass forming region in this pseudo-ternary system is compared with the conventionally melted glass forming region in the system AgI-Ag2O-B2O3. A reversible color difference has been observed between glasses conventionally melted and those melted by microwave for all glass compositions in our system.
Complex Permeability Measurements of Microwave Ferrites1
Authors: Geyer Richard G. , Krupka Jerzy
Published: April 2011

A rigorous and accurate method for the experimental determination of the complex permeability of demagnetized ferrites at microwave frequencies is presented. The measurement uses low- loss dielectric ring resonators, is nondestructive, and allows complex permeability characterization of a single ferrite sample to be performed at frequencies from 2 GHz to 25 GHz. A wide variety of ceramic microwave ferrites having various compositions and differing saturation magnetizations were measured in the demagnetized state. Generally, at any frequency greater than gyromagnetic resonance, the real part of the complex permeability increases as saturation magnetization increases.For the same frequency magnetic losses increases as saturation magnetization increases. The real permeability results are compared with magnetostatic theoretical predictions. Measurement data show excellent agreement with theoretical predictions, but only when 2πγMs/ω < 0.75, where γ is the gyromagnetic ratio, Ms is saturation magnetization, and ω is the radian rf frequency.
Microwave Dielectric Properties, Thermal Analyses And Chemical Composition Of Heavy Clay Bodies
Authors: Tayler Garth , Hamlyn Michael , Anderson Michael
Published: April 2011

To investigate the suitability of heavy clay bodies for microwave processing, a range of material properties needed to be investigated.

This paper presents results of the analyses, chemical, mineralogical and thermal, of a range of heavy clay bodies. The microwave dielectric properties of these bodies were measured, over a range of temperatures, using the cavity perturbation technique. The relationship between the dielectric properties and the results of DTA/TGA analysis is discussed and related to the potential use of microwave energy for the firing of these materials.
The MiRa/THESIS3D-Code Package for Resonator Design and Modeling of Millimeter-Wave Material Processing
Authors: Feher L. , Link G. , Thumm M.
Published: April 2011

Precise knowledge of millimeter-wave oven properties and design studies have to be obtained by 3D numerical field calculations. A simulation code solving the electromagnetic field problem based on a covariant raytracing scheme (MiRa-Code) has been developed. Time dependent electromagnetic field-material interactions during sintering as well as the heat transfer processes within the samples has been investigated. A numerical code solving the nonlinear heat transfer problem due to millimeter-wave heating has been developed (THESIS3D-Code). For a self consistent sintering simulation, a zip interface between both codes exchanging the time advancing fields and material parameters is implemented. Recent results and progress on calculations of field distributions in large overmoded resonators as well as results on modeling heating of materials with millimeter waves are presented in this paper. The calculations are compared to experiments.
Kinetics of the Carbon Monoxide Oxidation Reaction Under Microwave Heating
Authors: Perry W. Lee , Katz Joel D. , Rees Daniel , Paffett Mark T. , Datye Abhaya
Published: April 2011

915 MHz microwave heating has been used to drive the CO oxidation reaction over Pd/Al2O3 without significantly affecting the reaction kinetics. As compared to an identical conventionally heated system, the activation energy, pre-exponential factor, and reaction order with respect to CO were unchanged. Temperature was measured using a thermocouple extrapolation technique. Microwave-induced thermal gradients were found to play a significant role in kinetic observations.
Kinetics of Reduction of Iron oxides Using Microwaves as Power Source
Authors: Gomez I. , Aguilar J. , Gonzalez M. , Morales J.
Published: April 2011

This work deals with kinetic description of carbothermic reduction of iron oxides using microwaves as power source. Previous researches shown that it is possible to conduct this kind of processes successfully, but real kinetic comparisons between conventional and microwaves procedure have been presented partially. The aim of this work is to describe reduction kinetics, taking into account how the iron oxide is reduced by microwaves compared with conventional energy supply. In this study we used iron ore in pellet shape and dust. We found that both, pellet and dust reduction stops when it reaches approximately 40%, even at whole power
Modeling of Damage Evolution During Ion Implantation Into Silicon: A Monte Carlo Approach
Authors: Tian S. , Morris M. , Morris S. J. , Obradovic B. , Tasch A. F.
Published: April 2011

We present for the first time a physically based ion implantation damage model which successfully predicts both the as-implanted impurity range profiles and the damage profiles for a wide range of implant conditions for arsenic, boron, phosphorus, and BF2 implants into single-crystal (100) silicon. In addition, the amorphous layer thicknesses predicted by this damage model for high dose implants are also generally in excellent agreement with experiments. This damage model explicitly simulates the defect production and its subsequent evolution into the experimentally observable profiles for the first time. The microscopic mechanisms for damage evolution are further discussed.
Microstructural Observation of Focused Ion Beam Modification of Ni Silicide/Si Thin Films
Authors: Tanaka Miyoko , Furuya Kazuo , Saito Tetsuya
Published: April 2011

Focused ion beam (FIB) irradiation of a thin Ni2Si layer deposited on a Si substrate was carried out and studied using an in-situ transmission electron microscope (in-situ TEM). Square areas on sides of 4 by 4 and 9 by 9 μm were patterned at room temperature with a 25keV Ga+-FIB attached to the TEM. The structural changes of the films indicate a uniform milling; sputtering of the Ni2Si layer and the damage introducing to the Si substrate. Annealing at 673 K results in the change of the Ni2Si layer into an epitaxial NiSi2 layer outside the FIB irradiated area, but several precipitates appear around the treated area. Precipitates was analyzed by energy dispersive X-ray spectroscopy (EDS). Larger amount of Ni than the surrounding matrix was found in precipitates. Selected area diffraction (SAD) patterns of the precipitates and the corresponding dark field images imply the formation of a Ni rich silicide. The relation between the FIB tail and the precipitation is indicated.
Electrical Resistivity of Copper Films by Partially Ionized Beam Deposition
Authors: Han S. , Yoon K. H. , Kim K. H. , Jang H. G. , Choi S. C. , Jung H. J. , Koh S. K.
Published: April 2011

Copper films on Si(100) were prepared by partially ionized beam at 0 kV and 3 kV acceleration voltages in order to investigate effects of ion energy on electrical property with thickness. X-ray diffraction(XRD) pattern analysis was used to investigate crystallinity of the copper films, microstructure by Scanning electron microscope(SEM) and surface roughness by atomic force microscopy(AFM). The crystallinity of the copper films grown at the 3 kV was more (111) textured than that at the 0 kV. The copper films grown at the both conditions had nearly same grain size below a thickness of 1000 Å. The 1800 Å Cu film grown at the 3 kV was 3 times rough than that at the 0 kV. The resistivity of copper films increased due to surface and grain boundary scattering, and the change of resistivity was discussed in terms of surface roughness, grain size and film density assisted by average depositing energy.
Thermal Stability of Cu Films on Tin/Ti/Si(100) by Partially Ionized Beam Deposition
Authors: Jang H. G. , Kim K. H. , Choi D. J. , Han S. , Choi S. C. , Choi W. K. , Jung H-J. , Koh S. K.
Published: April 2011

Cu thin films with a thickness around 850 Å were prepared on Ti45N55/Ti/Si(100) substrates at room temperature by partially ionized beam deposition (PIBD) with an ion energy of 3 keV at pressure of 8×10−7–1 × 10−6 Torr. The Cu/Ti45N55/Ti/Si samples were annealed at 8× 10−6–1 × 10−5 Torr with annealing temperature of 500 to 700 °C for 30 min.. Thermal stability of the PIB-Cu films was investigated with Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), and X-ray diffraction (XRD).

The as deposited Cu films had a (111) texture and there was no change of phase in annealed Cu films regardless of annealing temperature. Grain size of the annealed Cu films increased with annealing temperature. SEM studies show no hillock and no voiding on the Cu film surface up to annealing temperature of 700 °C. For PIB-Cu/Ti45N55/Ti/Si samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques (RBS, AES) up to 700 °C in vacuum for 30 minutes.
In Situ Ion Beam Research In Argonne's Intermediate Voltage Electron Microscope
Authors: Allen Charles W. , Ryan Edward A.
Published: April 2011

Since Fall 1995, a state-of-the-art intermediate voltage electron microscope (IVEM) has been operational in the HVEM-Tandem Facility with in situ ion irradiation capabilities similar to those of the HVEM of the Facility. A 300 kV Hitachi H-9000NAR is interfaced to the two ion accelerators of the Facility, with a demonstrated point-topoint spatial resolution for imaging of 0.25 nm with the ion beamline attached to the microscope. The IVEM incorporates a Faraday cup system for ion dosimetry with measurement aperture 6.5 cm from the TEM specimen, which was described in Symposium A of the 1995 MRS Fall Meeting. The IVEM is now employed for a variety of in situ ion beam studies ranging from low dose ion damage experiments with GaAs, in which damage zones individual displacement cascades are observed, to implantation studies in metals, in which irradiation-induced noble gas precipitate mobility is studied in real time. In this presentation, the new instrumentation and its specifications will be described briefly, several basic concepts relating to in situ experiments in transmission electron microscopes will be summarized and examples of in situ experiments will be presented which exploit the experimental capabilities of this new user facility instrumentation.
Plastic Flow Induced by Single Ion Impacts on Gold
Authors: Birtcher R. C. , Donnelly S. E.
Published: April 2011

In situ transmission electron microscopy has been used to follow room temperature irradiation of thinned bulk and 62 nm thick gold films with Xe ions in the energy range 50 to 400 keV. Energy spikes resulting from single ion impacts give rise to surface craters and holes which exist until annihilation by subsequent ion impacts. Video recording provided details with a time-resolution of 33 milliseconds. Craters were produced on the irradiated surface at all ion energies and on the opposite surface when the ions had sufficient energy to traverse the specimen. Crater sizes were as large as 12 nm for the higher energy irradiations. On average, approximately 6% of impinging ions result in craters.

A single 200 keV Xe ion may produce a hole in thin gold foils. Hole formation involves the movement by plastic flow of massive amounts of material; on the order of tens of thousand Au atoms per ion impact. Individual ion impacts also result in a filling of both holes and craters as well as a thickening of the gold foil. Change in morphology during irradiation is attributed to a localized, thermal-spike induced melting, coupled with plastic flow under the influence of surface forces.
Specific Effects of the Displacement Cascades on the Kinetics of Precipitation of Copper in Iron
Authors: Barbu A. , Lesueur D. , Dural J.
Published: April 2011

Abstact

In order to probe the possibility of simulating irradiation effects with swift ions and obtaining some insight about the production rate of freely migrating defects in iron, we studied the kinetics of copper precipitation in FeCu1.34at% irradiated at 300°C with 202 MeV O- ions and 2.5 MeV electrons. The precipitation kinetics are studied in situ (GANIL for O- ions and Van de Graaff for electrons) by measuring the electrical resistivity at 30°C to reduce the phonon component. We found that, in both cases, the resistivity versus fluence (in dpa) curves are identical. This would imply either that the relatively small cascades induced by 202 MeV O- ions (compared with those produced by neutrons) are very efficient in producing freely migrating point defects or that the energy deposition by electronic excitations plays an important role. We show that this latter possibility is not relevant for 202 MeV O18 ions.
Characterization of Various Organic Coatings on Glasses
Authors: Lee Donghun , Condrate Robert A.
Published: April 2011

Organic compounds such as oleic acid, polymethyl methacrylate (PMMA) and polyacrylate (PAA) were coated on slide and silica glass powders. The resulting interaction mechanism was determined by the leaching properties of the glass, and the bond strength of each ion on the glass with coated organics. Soluble components such as sodium and calcium play important roles in the interaction properties of the organics with glass surfaces. The effects of solvent are also discussed.
Roughness Characterization by Optical Spectroscopy of CoSi2 Thin Films
Authors: Bocelli S. , Guizzetti G. , Marabelli F. , Hatziconstantinidou S. , Petersson C.S.
Published: April 2011

Specular and diffuse reflectance and spectroscopic ellipsometry were used to characterize a series of Cosi2 films obtained by heat treatment on a Co/Ti bilayer. The surface quality is strongly affected by etching procedures. The intrinsic optical properties of the CoSi2 film exhibit a small dependence on the growth technique.
An Investigation Of Vacancy Population During Arsenic Activation In Silicon
Authors: Dokumaci O. , Gossmann H.-J. , Jones K. S. , Law M. E.
Published: April 2011

Recent experimental investigations have shown that electrical deactivation of arsenic in silicon creates excess silicon interstitials. This study investigated the possibility of excess vacancy generation during arsenic activation. We used Sb doping superlattice structures containing six 10 nm wide Sb doped spikes separated by 100 nm. It was found that antimony diffusion was not enhanced as active arsenic concentration increased, indicating there is no observable vacancy injection out of the arsenic layer during the activation process. Plan-view transmission electron microscopy study of the samples revealed dislocation loops before the activation anneal. Although the loops completely dissolved during the activation anneal, they do not seem to be sufficient enough to absorb all the vacancies generated by the activated arsenic. When germanium was present at the surface instead of arsenic, antimony diffusion was enhanced.
Gettering of FE By Aluminum In P-Type Cz Silicon
Authors: Ahn S. H. , Zhao S. , Smith A. L. , Chalfoun L. L. , Platero M. , Nakashima H. , Kimerling L. C.
Published: April 2011

In this study, we investigate the gettering process of Fe in p-type Cz silicon after iron has been introduced at the solubility limit at 1000°C. Deep Level Transient Spectroscopy (DLTS) was used to measure [FeB], a fingerprint of [Fei], at the center of samples. The minority carrier diffusion length and lifetime were calculated from Electron Beam Induced Current (EBIC) measurements. The fact that [FeB] is proportional to the negative second power of the minority carrier diffusion length at the high [FeB] regime confirms that FeB donors are the dominant recombination centers limiting solar cell performance with high Fe contamination. By quenching after heat treatment, we can maintain and measure the kinetics and thermodynamics of gettering exclusively. The getter/silicon interface was studied by comparison of the gettering rates of molten Al at 620°C, 700°C, and 800°C, and iron silicide at 700°C. We model Fe gettering with respect to temperature, time, solubility and precipitate nuclei density. In the early stage of Fe gettering, the process is dominated by precipitate formation around oxygen precipitate nuclei. The precipitate density is estimated to be on the order of 5×108cm−3. In later stages, Fe outdiffusion contributes to the [Fei] reduction. The early stage precipitation limits [Fei] reduction after short time to the solubility at the gettering temperature.
Optical Nmr From Single Quantum Dots
Authors: Brown S. W. , Kennedy T. A. , Gammon D.
Published: April 2011

We have observed nuclear magnetic resonance (NMR) signatures from constituent Ga and As nuclei in single GaAs quantum dots formed by interface fluctuations in GaAs/AlGaAs quantum wells. Orientation of the nuclear spin system by optical pumping causes an Overhauser shift in the excitonic energy levels proportional to the degree of nuclear orientation. NMR was detected by monitoring changes in the combined Overhauser plus Zeeman splitting of an exciton localized in a single quantum dot as the RF frequency was swept through a nuclear resonance. The NMR signals originate from ∼105 nuclei in the quantum dot — (20 nm)3 volume - representing an increase in sensitivity of five orders of magnitude over previous optical NMR measurements and thirteen orders of magnitude over conventional NMR. The data were fit to Lorentzian lineshapes, giving 75As linewidths on the order of 20 kHz.
Ctivation Energies Of Interstitial Oxygen Diffusion In Silicon Containing Hydrogen
Authors: Wijaranakula W.
Published: April 2011

The activation energies of interstitial oxygen diffusion in silicon containing hydrogen were derived from the results obtained from thermal donor generation experiments using numerical fitting based upon the classical nucleation rate theory and the time-dependent reduction of interstitial oxygen concentration resulting from oxygen aggregation. By using a new thermal equilibrium concentration of hydrogen at a pressure of 1 atm of 2×1021 exp(- 1.75 eV/kT), and the expression for the dependence of hydrogen thermal equilibrium concentration on the partial pressure P given as P0.65 times the hydrogen thermal equilibrium concentration at a pressure of 1 atm, the correlation between the activation energies of interstitial oxygen diffusion and hydrogen saturation is observed to be linearlogarithmic. In the hydrogen saturation range between 103 and 106, the activation energies of interstitial oxygen diffusion are estimated to be between 0.03 and 0.21 eV lower than the normal value of 2.53 eV. This implies that enhanced oxygen diffusion may occur primarily under hydrogen saturation conditions.
An Anomalous Deep Center (EC-0.31 Ev) in Semi-Insulating GaAs
Authors: Fang Z-Q. , Look D. C.
Published: April 2011

A prominent deep center in semi-insulating GaAs, T5 at Ec×0.31 eV, has been studied by thermally stimulated current (TSC) spectroscopy using variation of illumination energy, intensity, and time. Unlike the case for most of TSC traps, the steady-state (long illumination time) peak intensity of T5 varies with light intensity. With the additional evidence that T5 seems to be related to both AsGa and VAs, it is possible that a photoinduced interaction AsGa.-VAs→VGa,-Asi-VAs is taking place.
Deep Level Transient Spectroscopy Study Of High-Temperature Aluminum Implanted 6H-SiC
Authors: Stotski Yuri A. , Usov Igor O. , Suvorov Alexander V.
Published: April 2011

Deep levels in 6H-SiC wafers implanted with Al+ ions at high-temperature were studied using current deep level transient spectroscopy (iDLTS). Aluminum was implanted at a temperature of 1800 °C with an energy of 40 keV and a dose of 2 × 1016 cm−2 into n-type epitaxial layers with different carrier concentration. Four levels were found, at Ec−0.12, Ec−0.13, Ec−1.06 and Ev+0.35 eV. It was established that modification of the carrier concentration in original ntype 6H-SiC epitaxial layers affects the deep levels concentration. The relationship between the thickness of the space charge region and the relative deep level concentration was considered.
Stabilization of Hydrogen‐Free Cvd‐ Sio2 Films
Authors: Uchida Y. , Takei S. , Matsumura M.
Published: April 2011

Annealing effects have been investigated for the SiO2 films deposited from a Tetra‐Iso‐Cyanate‐Silane and Tertiary‐Alkyl‐Amine gas mixture in order to stabilize its desirable hydrogen‐free property. It was found that O3 annealing eliminates effectively the NCO‐group from the deposited film, resulting in the improved water resistance characteristics, and that HF changes the Si‐NCO bonds to Si‐F bonds resulting also in improved film properties.
Very Thin Films of High Dielectric Constant Materials
Authors: Beach David B. , Vallet Catherine E. , Paranthaman Mariappan
Published: April 2011

An all‐alkoxide route to SrBi2Ta2O9 (SBT) thin films and powders was developed. While stoichiometric gels transformed to single‐phase SBT, excess bismuth was required to obtain single‐phase SBT films on Pt substrates. An annealing temperature of 800 °C in O2 for 2 minutes was required to crystallize the films. Electrical measurements of SBT films produced under these conditions showed that films less than 2000 Å in thickness were shorted, while films of 3000 to 5000 Λ had a dielectric constant of~ 300. RBS measurements of a bismuth titanate film on Pt indicated that Pt diffuses into the dielectric layer when annealed at 700 °C in O2 for 1 minute, suggesting that interfacial reaction of these layered bismuth materials may be significant.
Novel Mocvd Processes for Nanoscale Oxide Thin Films
Authors: Li Tingkai , Zawadzkp Pete , Stall Richard A. , Zhu Yongfei , Desu Seshu B.
Published: April 2011

Nanoscale oxide thin films such as Ba1‐xSrxTiO3 (BST), SrBi2Ta2O9 (SBT), and PbZr1‐xTixO3 (PZT) that have a high dielectric constant and excellent ferroelectric properties have been receiving greatly increased attention, especially for high density memories in next generation integrated circuits. However, with increasing deposition temperature the surface roughness of the films increases, which results in high leakage current, and when the thickness of oxide films is decreased, the apparent bulk‐like properties of thin films tend to worsen due to the increased influence of the interface. To solve these problems, novel MOCVD techniques, plasma enhanced deposition, and a two step process, were developed for high quality oxide thin films.
Optical Characterization of Europium-Doped Calcium Fluoride Thin Films Grown on Silicon by Molecular Beam Epitaxy
Authors: Fang X.M. , Liu W.K. , Shan W. , Chatterjee T. , Mccann P.J. , Santos M.B. , Song J.J.
Published: April 2011

Photoluminescence measurements have been made on Eu-doped CaF2 thin films grown on Si(100) substrates. The dependence of the integrated intensity of both the zero-phonon line and the vibronic sideband on temperature and Eu concentration has been studied in the range of 10 – 300 K and 0.14 – 7.48 at. %, respectively. An anti-Stokes feature is visible in the emission spectra at 75 K, indicating a significant occupation of the excited vibrational states of Eu2+ by phonons before the transition at temperatures above 75 K. The integrated intensity of the vibronic sideband increases slightly as temperature increases. The solubility of Eu in CaF2 thin films grown on Si(100) is found to be somewhere around 4.05 at. % as confirmed by the increase of the line width of x-ray rocking curves and the decrease in the integrated intensity of the zero-phonon line with Eu concentration.
Photoresist Polymer Mask Formed From Aqueous Phase Via Polymerization In A Two Dimensional Surfactant Template
Authors: Newman P. D. , Newman G. K. , Harwell J. H.
Published: April 2011

An environmental friendly, aqueous based, thin film technology is investigated that is quite versatile in forming a variety of polymer substrates. The polymer substrates are potentially capable of being utilized as high resolution resists for semiconductor chip production. This process is based on polymerization of monomers partitioned within a two dimensional surfactant template adsorbed on the surface of a silicon wafer. The surfactant template (bilayer) serves to localize the polymerization reaction at the liquid‐solid interface and thereby resulting in the coverage of the silicon wafer with a nano‐thin polymer film. On a polished silicon wafer with a 4 nm silicon oxide layer, film thickness up to 130 nm have been obtained for polystyrene and for poly(methyl methacrylate) (PMMA) which is also used as a standard photoresist mask in electron beam lithography.
Cavities for Intersubband Transitions
Authors: Berger V. , Duboz J-Y , Ducloux E. , Lafon F. , Pavel I. , Boucaud P. , Gauthier-Lafaye O. , Julien F. , Tchelnokov A. , Planel R.
Published: April 2011

The different possible geometries for intersubband transitions in microcavities are discussed. A consequence of the selection rule governing intersubband transition is the vanishing interaction with the electromagnetic field inside a usual vertical cavity. The geometry of vertical planar cavities which has been used extensively with interband transitions is therefore useless in the case of intersubband transitions. Different solutions are reviewed to overcome this problem. The breakdown of the selection rule in a vertical cavity is first discussed. This can be done with the use of vertical quantum wells, or thanks to intracavity diffraction gratings. Second, the use of in plane cavities is discussed. Two solutions are here envisaged: Whispering gallery modes in microdisk cavities, and efficient etched air/GaAs Bragg mirrors. Concerning the latter attractive solution, the losses by diffraction into the substrate are evaluated theoretically and experimentally. The solution of the Maxwell equations by a finite element method in this three dimensional system shows the great importance of diffraction. These results are confirmed by waveguided Fourier transform spectroscopy. To overcome this difficulty, we propose the use of lower refractive index substrates, such as oxidized AlAs.
Theoretical Studies of Electronic Intersubband Transitions in n-Type Doped Quantum Wells for Infrared Photodetector Applications
Authors: Huang Danhong , Manasreh M. O.
Published: April 2011

A self-consistent (8 × 8)-k · P model based on the Kohn-Sham density-functional formalism is used to calculate the quasi-particle wave functions and energy levels in n-type doped quantum wells. The self-energy from electron-electron, electron-impurity, and electron-phonon scattering was included in the calculation. The electronic intersubband absorption was calculated using a generalized self-consistent-field method including the vertex correction. The theoretical approach was applied to explain the variation of the intersubband transition peak energies as the temperature or the electron density is changed. Good agreement between the theory and experiment was achieved. The present theoretical model was also applied to design two-colors quantum well infrared photodetectors and was found to agree with the experimental measurements. Based on the numerical calculation, an approach to realize the three-colors infrared photodetectors in the triple-coupled quantum wells was proposed.
Inelastic Light Scattering in Zinc Germanium Diphosphide Crystals
Authors: Bairamov B. H. , Negoduyko V. K. , Rud Yurri V. , Toporov V. V. , Voitenko V. A. , Schunemann P. G. , Fernelius N. , Ohmer M. C. , Jackson H. E.
Published: April 2011

The inelastic light scattering spectra of chalcopyrite structure ZnGeP2 crystals grown by an improved low temperature crystallization from the nonstoichiometric solution of this compound in the liquid Bi or liquid Tl solutions as well as grown by high temperature Bridgman technique has been investigated together with the optical absorption and electron transport measurements.
Sputter Deposition of Semiconductor Superlattices for Thermoelectric Applications
Authors: Wagner Andrew V. , Foreman Ronald J. , Farmer Joseph C. , Barbee Troy W.
Published: April 2011

Theoretical dramatic improvement of the thermoelectric properties of materials by using quantum confinement in novel semiconductor nanostructures has lead to considerable interest in the thermoelectric community. Therefore, we are exploring the critical materials issues for fabrication of quantum confined structures by magnetron sputtering in the lead telluride and bismuth telluride families of materials. We have synthesized modulated structures from thermoelectric materials with bilayer periods of as little as 3.2 nm and shown that they are stable at deposition temperatures high enough to grow quality films. Issues critical to high quality film growth have been investigated such as nucleation and growth conditions and their effect on crystal orientation and growth morphology. These investigations show that nucleating the film at a temperature below the growth temperature of optimum electronic properties produces high quality films. Our work with sputter deposition, which is inherently a high rate deposition process, builds the technological base necessary to develop economical production of these advanced materials. High deposition rate is critical since, even if efficiencies comparable with CFC based refrigeration systems can be achieved, large quantities of quantum confined materials will be necessary for cost-competitive uses.
InSb Detectors and Focal Plane Arrays on GaAs, Si, and Al203 Substrates
Authors: Michel E. , Mohseni H. , Wojkowski J. , Sandven J. , Xu J. , Razeghi M. , Vu P. , Bredthauer R. , Mitchel W. , Ahoujja M.
Published: April 2011

In this paper, we report on the growth and fabrication of InSb detectors and Focal Plane Arrays (FPA's) on (100) Si, Al203, and (100) and (111) GaAs substrates for infrared (IR) imaging. Several advantages result from using GaAs, Si, or Al203. First, InSb FPA's on these materials do not require thinning as with detectors fabricated from bulk InSb. In addition, these substrates are available in larger sizes, are semi-insulating (GaAs and sapphire), and are less expensive than InSb.

Optimum growth conditions have been determined and discrete devices have been fabricated on each substrate material. The structural, electrical, and optical properties were verified using x-ray, Hall, photoresponse, and photoluminescence (PL) measurements. Measured x-ray Full Widths at Half Maximum (FWHM) were as low as 55 and 100 arcsec for InSb epilayers on GaAs and Si, respectively. Hall mobilities were as high as 128,000, 95,000 and 72,000 cm2/V-sec at 200 K, 77 K, and room temperature, respectively. In addition, 77 K PL linewidths were as low as 18, 20, and 30 meV on GaAs, Si, and sapphire substrates respectively, well below the 48 meV value previously reported in the literature.

In collaboration with Lockheed Martin Fairchild Systems (LMFS), IR thermal imaging has been obtained from InSb FPA's on GaAs and Si substrates. This is the first successful IR thermal imaging from heteroepitaxially grown InSb. Because of the high quality substrates, larger areas, and higher yields, this technology is very promising for challenging traditional InSb FPA hybrid technology.
Atomic-Scale Simulations of Structural Properties of Ceramics
Authors: Keffer D. J. , Streitz F. H. , Mintmire J. W.
Published: April 2011

We have recently developed a novel computational method for molecular dynamics simulations of metal oxide ceramics. This approach explicitly includes variable charge transfer between anions and cations. This method has been used to model the structural properties of bulk and surface alumina and aluminum systems including tensile failure of the bulk systems, as well as to model the rupture under tensile stress of an interface between a (0001) face of a-alumina and a (111) face of aluminum. We have applied this method to perform atomic-scale simulations of nanoindentation of ceramic and model rigid tips onto metal and ceramic substrates.
A Theoretical and Experimental Study of the Chemical Bonding in AgGaS2
Authors: Continenza Alessandra , de Pascale Teresa M. , Meloni Franco , Serra Marina , Shaukat Ali , Burzlaff Hans , Spengler Roland
Published: April 2011

AgGaS2 is a technologically important semiconductor for its large birefringence coefficient. In this work we compare the theoretical ab-initio all-electron FLAPW results with very refined experimental data obtained with accurate X-ray analysis. In particular we focus our attention to the electronic distribution along the significative bonding directions connecting the three different atoms. Furthermore, the charge density contours around Ag provide a clear evidence of the contribution of its d orbitals to the chemical bond.
Synthesis of Ferroelectric Strontium Bismuth Tantalate Films from Metal Alkoxide Precursors
Authors: Zhuang Wei-Wei , Liu Lumei , Wu Naijuan , Hao Zhidong , Hoffman David M. , Ignatiev Alex , Jacobson Allan J. , Perry Scott S.
Published: April 2011

Ferroelectric SrBi2Ta2O9 (SBT) films were prepared by the spin coating technique on platinum, quartz and YBa2Cu3O7-x/LaA1O3 substrates from a methoxyethanol solution of bismuth isopropoxide (Bi(OCH(CH3)2)3) and strontium tantalum isopropoxide (SrTa2(OCH(CH3)2)12). X-Ray diffraction studies showed some crystallization occurred after annealing the films under oxygen flow at 600 °C and excellent crystallinity was achieved after annealing at 750 °C for 0.5 h. Electron microprobe analysis gave a composition close to that expected for SBT, and atomic force microscopy gave a root mean square surface roughness of 101 A. An hysteresis measurement (1 kHz) gave remnant polarization (2Pr), saturation polarization (Ps) and coercive field (Ec) values of 14.5 μC/cm2, 14.5 μ/cm2 and 59 kV/cm, respectively.
Zeolite Sensor for Nitrogen Monoxide Detection at High Temperature
Authors: Tsuchiya Hiroshi , Sasaki Isao , Harano Azuchi , Okubo Tatsuya , Sadakata Masayoshi
Published: April 2011

Development of new NOx sensors, which would be sensitive, selective, inexpensive and stable at elevated temperature, will greatly contribute to the reduction of the air pollution. In this paper, synthesis and performance of zeolite film applied for gas sensing are reported.

Zeolite thin films (Cu ion-exchanged ZSM-5) were synthesized on the gold electrode of AT-cut quartz platelet by hydrothermal synthesis. In order to probe the target molecule (NO) selectively, Na in as synthesized ZSM-5 film was ion-exchanged with Cu. The films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The synthesis condition for orientation to (0×0) face, on which the straight pores of ZSM-5 are opening, was optimized.

The bulk type quartz oscillator coated with Cu-ZSM-5 thin layer was tested as NO sensor in a flowing stream of He. This sensing system could be operated at high temperature because of the thermal stability of the ZSM-5 film and the gold electrode. As a result, NO was successfully detected at 348 K.
High Surface Area Silicon Carbide Doped with Zirconium for use as Heterogeneous Catalyst Support
Authors: Ledoux Marc J. , Pham-Huu Cuong , Bouchy Christophe , Gallo Pascal Del , Estournes Claude , Crouzet Claude , Heinrich Baudouin
Published: April 2011

High surface area (> 100 m2 · g−1) SiC doped with zirconium was prepared by the gas-solid reaction. The material was made up of three phases: β-SiC, covered by ZrO2 and an amorphous phase composed of Si, Zr and O. The characterization of the sample was performed by means of powder X-ray diffraction (XRD), surface area and porosity measurements by the BET method, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Preliminary catalytic tests, the standard n-C7 isomerization on supported MoOxCy showed that this new support was at least as effective as pure SiC.
Supported Molybdenum Carbide Catalysts: Structure-Function Relationships for Hydrodenitrogenation
Authors: Dolce Gregory M. , Thompson Levi T.
Published: April 2011

Early transition metal carbides and nitrides have been shown to be active for the hydrotreatment of model compounds and petroleum crudes. In this paper we describe our investigations of the structural and compositional properties of γ-Al2O3-supported molybdenum carbides and efforts to correlate these properties with their pyridine and quinoline hydrodenitrogenation (HDN) activities. The HDN activities of the materials scaled linearly with the loading and oxygen chemisorptive uptake. Oxygen chemisorption results also suggested that the molybdenum carbide particles were highly dispersed and perhaps raft-like. Using temperature programmed desorption and infrared spectroscopy of carbon monoxide, we were able to identify two types of sites on the carbides; sites “on top” of the particle and sites at the perimeter. We have tentatively concluded that the most active sites for HDN were “on top” of the supported carbide particles.
Synthesis and Characterization of Hydrotalcites: [Zn1−xAlx(OH)2](CO3)x/2·mH2O; x=0.25−0.66
Authors: Valenzuela M. A. , López-Salinas E. , Zapata B. , Montoya J. A.
Published: April 2011

In this work a series of [Zn1−xAlx(OH)2](CO3)x/2·mH2O; x=0.25−0.66 were prepared at constant pH in order to study the effect of the thermal treatment on their crystalline srtucture. It was found that is possible to obtain pure Zn-Al hydrotalcite materials within a x = 0.25−0.50 range in comparison with Mg-Al hydrotalcites which yield pure phases in more restricted x ranges (0.25−0.33). All Zn-Al hydrotalcites lost their layered structure at temperatures above 473 K being less stable than their parental Mg-Al hydotalcite (623 K). Specific surface areas of these materials depended strongly on the Zn/Al ratio and calcination temperature, ranging from 280 to 20 m2/g. ZnO and ZnAl2O4 compounds were detected as the calcination products at temperatures higher than 873 K.
Separation of Diffusive Jump Motion and Trapped Motion of Atoms in a Glass Forming Process Via Molecular Dynamics Simulation
Authors: Matsui J. , Fujisaki M. , Odagaki T.
Published: April 2011

We have carried out the molecular dynamics (MD) simulation for a binary soft-sphere system and calculated the self part of the generalized susceptibility χs(q, ω) at various temperatures. At higher temperatures in liquid state, only one peak appears in the imaginary part of Xa, which tends to split into two peaks, the so-called α- and β- peaks, as the temperature is reduced. The temperature dependence of the peak frequency is well described by the Vogel-Fulcher law for the α- peak, and the peak frequency does not change much for the α- peak. We have also measured the trajectory volume of a tagged atom V(t), which is related to the dynamical order parameter, the “generalized capacity”, in structural glass transitions recently proposed by J. F. Douglas. These results show the transition temperature which is in good agreement with that determined by the trapping diffusion model.
Glass Formation and Local Topological Instability of Atomic Structure
Authors: Egami T.
Published: April 2011

A direct connection between the local topology of the atomic structure of liquids and glasses and thermodynamic quantities through the atomic level stresses is suggested for metallic alloys. In particular the role of local topological instability in the phase transformations involving liquid and glass will be discussed. It is pointed out that a single local geometrical criterion can explain various phase transformations, such as melting, glass transition, and glass formation by solid state reaction and liquid quenching.
Dynamics of a Supercooled Lennard-Jones System: Qualitative and Quantitative Tests of Mode-Coupling Theory
Authors: Kob Walter , Nauroth Markus
Published: April 2011

We present the results of a molecular dynamics computer simulation of a supercooled binary Lennard-Jones mixture. By investigating the temperature dependence of the diffusion constant and of the intermediate scattering function, we show that the ideal version of the mode-coupling theory of the glass transition is able to give a good qualitative description of the dynamics of this system. Using the partial structure factors, as determined from the simulation, as input, we solve the mode-coupling equations in the long time limit. From the comparison of the prediction of the theory for the critical temperature, the exponent parameter, the wave-vector dependence of the nonergodicity parameters and the critical amplitudes with the results of the simulation, we conclude that the theory is also able to predict correctly the non-universal properties of the dynamics of a supercooled simple liquid.
The Influence of Fiber/Matrix Interface on the Mechanical Behavior of Nicalon SiC Fiber Reinforced Glass-Ceramic Composites
Authors: Liu Y. M. , Mitchell T. E. , Wadley H. N. G.
Published: April 2011

The mechanical properties of unidirectional Nicalon SiC fiber reinforced calcium aluminosilicate (CAS/SiC) and magnesium aluminosilicate (MAS/SiC) glass-ceramic composites have been investigated by tensile testing and a nondestructive laser-ultrasound technique. The barium-stuffed MAS was either undoped or doped with 5% borosilicate glass. The degradation of the elastic stiffness constant Cu in the transverse direction due to interface damage was monitored in-situ by measuring the laser-generated ultrasound wave velocity. The three composite materials show distinctly different macroscopic deformation characteristics, which are correlated strongly to the interface degradation. A stronger reduction trend of the elastic constant ?? is associated with a larger degree of inelastic deformation. Observations of the fracture surfaces also reveal the close relation between fiber pullout length and interfacial characteristics. Interfaces of these composites have been studied by TEM, and their influence on inhibiting and deflecting matrix cracks is discussed.
Characterization of Diffusion Barrier Interlayers Between Copper and Plasma Sprayed Beryluum
Authors: Bartlett A. H. , Castro R. G.
Published: April 2011

Plasma spraying is being investigated as a method to fabricate first wall Be armor for the International Thermonuclear Experimental Reactor. Diffusion barriers of Ti, V, and W were deposited between the Be and the Cu substrate, also by plasma spray, to prevent formation of brittle Be-Cu intermetallics. Interface fracture toughness tests revealed loading mode-dependent crack behaviors and interface fracture toughnesses.
Hard and Soft Composition Lead Zirconate Titanate Thin Films Deposited by Pulsed Laser Deposition
Authors: Lacey Johanna L. , Trolier-McKinstry Susan
Published: April 2011

Lead zirconate titanate thin films offer considerably larger piezoelectric coefficients than do ZnO, and so are attractive for microelectromechanical sensors and actuators. To date, much of the research in this field has concentrated on undoped PZT. In this work, PZT films grown from both hard and soft PZT targets have been deposited on platinum coated silicon wafers by pulsed laser deposition so that the effect of doping on the properties can be determined. Dielectric constants of 1000–1500 are regularly achieved in both types of films, with loss values varying from 0.01 for soft films to 0.03 for hard films. Remanent polarizations are typically 30 μC/cm2 for both types of films with no observable difference in coercive fields. When subjected to ∼140 MPa of biaxial tension and compression, only small (∼5%) reversible changes were observed, indicating a lack of substantial domain reorientation in the films.
Effect of Nitrogen on Shape Memory Behaviour of FE-MN-SI-CR-NI Alloys
Authors: Ariapour A. , Perovic D. D. , Mclean A.
Published: April 2011

The composition of an Fe-Mn-Si-Cr-Ni stainless steel with shape memory effect was altered in this work in order to increase the strength of the alloy. The alloy possessed a low yield strength which is a major draw back for structural applications.

Nitrogen alloying, using nitrogen pressurized melting (P=l–10 atm), was employed to introduce a nitrogen concentration of up to 0.36 wt%. The effect of nitrogen alloying on shape memory effect was studied through mechanical testing. It was found that nitrogen alloying increased the hardness; however, nitrogen as an interstitial alloying element suppressed the γ⇒ε transformation and therefore decreased the shape memory effect.

Introducing small amount of Nb (e. g., 0.36 wt%) to the nitrogen containing alloys caused formation of NbN. The NbN compound was in the form of globular dispersed particles (200 nm) which increased the strength of the alloy without significantly changing the shape memory effect.
Smart Composite Biomaterials TiAIV/AI2O3/TiNi
Authors: Filip Peter , Musialek Jaroslav , Kneissl Albert C. , Mazanec Karel
Published: April 2011

The TiNi shape memory alloy wires were plasma coated by α-Al2O3 ceramics and afterwards they were cast into Ti6Al4V or Ti6Al1.5V2.5Nb (Ti-alloy) matrix. The wire fibers melt and the alumina ceramics reacts with both TiNi and Ti-alloy if cooling rate is small. The interphases which are formed are Ti2(Al, Ni) and Ti3AL-type phases, respectively. The structure of TiNi wires changes to dendritic one, Ti-alloys contain 10 to 15% of primary α and transformed β phase. The optimal conditions for rolling are 900°C with reductions of 5%. At this conditions all the constituents of composite material can be deformed plastically. The adhesive strength of TiNi/Al2O3 is 60 MPa.
Characterization and Electrical Properties of WO3 Sensing Thin Films
Authors: Cantalini C. , Di Nardo S. , Lozzi L. , Passacantando M. , Pelino M. , Phani A. R. , Santucci S.
Published: April 2011

The microstructure and the electrical properties of thermallyevaporated WO3 thin films have been investigated by glancing angle XRD, atomic force microscopy AFM, X-ray photoelectron spectroscopy XPS and dc techniques. Thin films of 1500 Å thickness have been obtained by evaporating high purity WO3 powders by an electricallyheated crucible at 5 × 10−4 Pa on sapphire substrates. Theas-deposited films have resulted to be amorphous. After annealing at 500°C in dry air for 6, 12 and 24 hours the films have shown well crystallized structures with preferential orientations of WO3 in the (200)direction. The increase of the annealing time has shown marked influence onthe microstructural features of the films surface, as highlighted by AFM investigations. The binding energies of W 4f7/2 have been close to that of WO3, the 24 h annealed yielded an O/W ratio close to 2.9 which is in good agreement with the theoretical one. The gas sensitivity, selectivity and stability of the annealed films in presence of NO2 gas (between 0.7 and 5 ppm) have been evaluated by measuring the electrical change of the film resistance in dry air and in gasatmosphere conditions. The influence of NO and Humidity interfering gases to the NO2 electrical response has been also evaluated. The 500 °C annealed at 24 h has shown better electrical properties in terms of NO2 sensitivity, stability and cross sensitivity effects.