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Articles 3751 - 3780 of 3840
Full-Text Articles in Physical Sciences and Mathematics
Remarks On A Semilinear Elliptic Equation On Rn, Yi Li
Remarks On A Semilinear Elliptic Equation On Rn, Yi Li
Mathematics and Statistics Faculty Publications
No abstract provided.
Spectral Measures, Orthogonal Polynomials, And Absolute Continuity, Joanne Dombrowski
Spectral Measures, Orthogonal Polynomials, And Absolute Continuity, Joanne Dombrowski
Mathematics and Statistics Faculty Publications
This paper studies the spectral measure of an unbounded tridiagonal matrix operator for which the matrix entries satisfy a certain growth condition, and presents a sufficient condition for the existence of an absolutely continuous part. The results are related to a class of orthogonal polynomials with exponential weights.
A Tool For Integrating Conceptual Schemas And User Views, Amit P. Sheth, James A. Larson, Aloysius Cornelio, Shamkant B. Navathe
A Tool For Integrating Conceptual Schemas And User Views, Amit P. Sheth, James A. Larson, Aloysius Cornelio, Shamkant B. Navathe
Kno.e.sis Publications
An interactive tool has been developed to assist database designers and administrators (DDA) in integrating schemas. It collects the information required for integration from a DDA, performs essential bookkeeping, and integrates schemas according to the semantics provided. The authors present the capabilities of this tool by discussing the integration methodology and the user interface of the tool.
On Conformal Scalar Curvature Equations In Rn, Yi Li, Wei-Ming Ni
On Conformal Scalar Curvature Equations In Rn, Yi Li, Wei-Ming Ni
Yi Li
No abstract provided.
On Conformal Scalar Curvature Equations In Rn, Yi Li, Wei-Ming Ni
On Conformal Scalar Curvature Equations In Rn, Yi Li, Wei-Ming Ni
Mathematics and Statistics Faculty Publications
No abstract provided.
Contact Resistance Measurements In Gaas Mesfet's And Modfet's By The Magneto‐Tlm Technique, David C. Look
Contact Resistance Measurements In Gaas Mesfet's And Modfet's By The Magneto‐Tlm Technique, David C. Look
Physics Faculty Publications
The standard transmission‐line model (TLM) for specific contact resistivity measurements of planar contacts is improved in two ways: (i) the addition of a magnetic field, which gives the mobility and carrier concentration of the bulk material, and the mobility of the material under the contact; and (ii) an extension to two layers, which makes the model applicable to MODFET structures. The results are applied to MESFET material, and MODFET material. One conclusion concerning the latter material is that the electrons directly beneath the annealed Au/Ge/Ni contacts have lower mobility than those in the bulk, but still …
Equivalence Of Donor And Acceptor Fits To Temperature-Dependent Hall Data: General Case, David C. Look
Equivalence Of Donor And Acceptor Fits To Temperature-Dependent Hall Data: General Case, David C. Look
Physics Faculty Publications
Recently, it was shown that the usual statistical-mechanical formulation used to fit carrier concentration versus temperature data cannot distinguish between the donor or acceptor nature of one single-charge-state center. Here we generalize that result to include any number of donor and acceptor centers, of arbitrary charge multiplicity, and also show how that by fitting one particular case (e.g., every center assumed to be a donor), all of the other possible cases can be immediately solved by inspection.
Defect Production In Electron-Irradiated, N-Type Gaas, David C. Look, J. R. Sizelove
Defect Production In Electron-Irradiated, N-Type Gaas, David C. Look, J. R. Sizelove
Physics Faculty Publications
Temperature-dependent Hall-effect measurements have been performed on pure, n-type, vapor-phase epitaxial GaAs, irradiated by 1-MeV electrons at room temperature. The energies and production rates of two dominant defect centers, C2 and C3, are as follows: E2 = EC - 0.148, E3 = EC2 = 2.0 and τ3 = 0.5 +/1 0.2 cm-1, in good agreement with deep level transient spectroscopy (DLTS) data. However, the most important result of this study is a very high production rate, τAS ≅ +/- 1 cm-1, for "shallow" acceptors (C …
Photoresistivity And Photo-Hall-Effect Topography On Semi-Insulating Gaas Wafers, David C. Look, E. Pimentel
Photoresistivity And Photo-Hall-Effect Topography On Semi-Insulating Gaas Wafers, David C. Look, E. Pimentel
Physics Faculty Publications
By placing a semi-insulating GaAs wafer on a fiat, rare-earth magnet, and irradiating the surface with two perpendicular slits of light to form a Greek cross configuration, it is possible to perform photoresistivity and photo-Hall-effect topography on the wafer. The technique is nondestructive in that the contacts are tiny, removable In dots which are placed only on the periphery. By varying the wavelength of the light, selective centers, such as EL2, can be mapped. We compare a 1.1-μ, photoexcited electron concentration map with a quantitative EL2 map on a 3-in. undoped, liquid-encapsulated Czochralski wafer.
Photoluminescence In Electrically Reversible (Semiconducting To Semiinsulating) Bulk Gaas, Phil W. Yu, David C. Look, W. Ford
Photoluminescence In Electrically Reversible (Semiconducting To Semiinsulating) Bulk Gaas, Phil W. Yu, David C. Look, W. Ford
Physics Faculty Publications
A photoluminescence study has been made of electrically reversible, bulk, liquid-encapsulated Czochralski GaAs at temperatures 2-300 K. The reversibility from the semiconducting to the semi-insulating state is made by slow or fast cooling, respectively, following a 5-h, 950°C heat treatment in an evacuated quartz ampoule. A donor level at Ec - 0.13 eV and two acceptor levels at Ev + 0.069 eV and Ev + 0.174 eV are produced after the heat treatment. Only the acceptor levels were detected by photoluminescence. A tentative model assigning the acceptor to the intrinsic defect pair VGa-GaAs is discussed.
Student Profile, Fall 1987, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Student Profile, Fall 1987, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Wright State University Student Fact Books
The student profile fact book has general demographic information on all students enrolled at Wright State University for Fall Quarter, 1987.
High Acceptor Production Rate In Electron-Irradiated N-Type Gaas - Impact On Defect Models, David C. Look
High Acceptor Production Rate In Electron-Irradiated N-Type Gaas - Impact On Defect Models, David C. Look
Physics Faculty Publications
Defect production rates have been studied in electron-irradiated GaAs by temperature-dependent Hall-effect (TDR) measurements. The TDH results agree well with deep level transient spectroscopy (DLTS) results for the wen-known electron traps E1, E2, and E3, but conclusively demonstrate a much higher production rate (4 ± 1 cm-1) of acceptors below E3 than the total of all other DLTS traps. These findings strongly affect current defect models, and, e.g., are consistent with the existence of Ga sublattice damage, not seen before.
Cyclic Operators, Commutators, And Absolutely Continuous Measures, Joanne Dombrowski
Cyclic Operators, Commutators, And Absolutely Continuous Measures, Joanne Dombrowski
Mathematics and Statistics Faculty Publications
Commutator equations are used to study the relationship between the tridiagonal matrix structure of an unbounded cyclic selfadjoint operator and its spectrum. Sufficient conditions are given for absolute continuity. Results are related to the study of systems of orthogonal polyomials for which the measure of orthogonality is supported on an unbounded subset of the real line.
Comparison Of Low-Energy Seismic Sources In Till, Paul J. Wolfe, B. H. Richard, Dale V. Dailey, James R. Plomer
Comparison Of Low-Energy Seismic Sources In Till, Paul J. Wolfe, B. H. Richard, Dale V. Dailey, James R. Plomer
Physics Faculty Publications
No abstract provided.
Equivalence Of Donor And Acceptor Fits Of Temperature-Dependent Carrier-Concentration Data, David C. Look, J. R. Sizelove
Equivalence Of Donor And Acceptor Fits Of Temperature-Dependent Carrier-Concentration Data, David C. Look, J. R. Sizelove
Physics Faculty Publications
It is shown that the usual charge-balance analysis of temperature-dependent carrier-concentration data cannot distinguish between the donor and acceptor behavior of a center which is emitting carriers to a particular band, even though the statistics are different in the two cases. Other data, such as mobility or analytical results are needed to make the distinction.
Electrical Characterization Of Ion Implantation Into Gaas, David C. Look
Electrical Characterization Of Ion Implantation Into Gaas, David C. Look
Physics Faculty Publications
Recent advances in the characterization of ion‐implanted samples have included whole wafer mapping (topography) and depth profiling techniques. We review several methods for mapping electrical parameters, including the dark‐spot resistance (DSR), and the microwave photoconductance techniques. In addition, we suggest a new photo‐Hall technique which would allow mobility and carrier‐concentration mapping as well as that of resistivity . Finally, we review methods for obtaining ρ, μ, and depth profiles, with particular emphasis on the application of the magnetoresistance techniques in actual field‐effect transistor structures.
Student Profile, Fall 1986, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Student Profile, Fall 1986, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Wright State University Student Fact Books
The student profile fact book has general demographic information on all students enrolled at Wright State University for Fall Quarter, 1986.
Semiconducting/Semi-Insulating Reversibility In Bulk Gaas, David C. Look, Phil W. Yu, W. M. Theis, W. Ford, G. Mathur, J. R. Sizelove, D. H. Lee, S. S. Li
Semiconducting/Semi-Insulating Reversibility In Bulk Gaas, David C. Look, Phil W. Yu, W. M. Theis, W. Ford, G. Mathur, J. R. Sizelove, D. H. Lee, S. S. Li
Physics Faculty Publications
Bulk, liquid-encapsulated Czochralski GaAs may be reversibly changed from semiconducting (ρ~1 Ω cm) to semi-insulating (ρ~107 Ω cm) by slow or fast cooling, respectively, following a 5 h, 950°C soak in an evacuated quartz ampoule. This effect has been studied by temperature-dependent Han-effect, photoluminescence, infrared absorption, mass spectroscopy, and deep level transient spectroscopy measurements. Except for boron, the samples are very pure, with carbon and silicon concentrations less than 3 X 1014 cm-3. Donor and acceptor concentrations, on the other hand, are in the mid 1015 cm-3 range, which means …
Semiconducting/Semi-Insulating Reversibility In Bulk Gaas, David C. Look, Phil W. Yu, W. M. Theis, W. Ford, G. Mathur, J. R. Sizelove, D. H. Lee, S. S. Li
Semiconducting/Semi-Insulating Reversibility In Bulk Gaas, David C. Look, Phil W. Yu, W. M. Theis, W. Ford, G. Mathur, J. R. Sizelove, D. H. Lee, S. S. Li
Physics Faculty Publications
Bulk, liquid‐encapsulated Czochralski GaAs may be reversibly changed from semiconducting (ρ∼1 Ω cm) to semi‐insulating (ρ∼107 Ω cm) by slow or fast cooling, respectively, following a 5 h, 950 °C soak in an evacuated quartz ampoule. This effect has been studied by temperature‐dependent Hall‐effect, photoluminescence, infrared absorption, mass spectroscopy, and deep level transient spectroscopy measurements. Except for boron, the samples are very pure, with carbon and silicon concentrations less than 3×1014 cm−3. Donor and acceptor concentrations, on the other hand, are in the mid 1015 cm−3 range, which means that …
Cooling By Immersion In Liquid Nitrogen, Thomas W. Listerman, Thomas A. Boshinski, Lynn F. Knese
Cooling By Immersion In Liquid Nitrogen, Thomas W. Listerman, Thomas A. Boshinski, Lynn F. Knese
Thomas Listerman
When an object is cooled by immersion in a liquid, there is an unexpected increase in the violence of boiling just before the boiling stops. Most people seem fascinated by this phenomenon yet few are acquainted with its explanation in terms of a change in the heat‐transfer mechanism from film boiling to nucleate boiling. We have developed two variations of an intermediate level undergraduate laboratory experiment to measure the heat‐transfer rate after a sample is immersed in liquid nitrogen. The temperature of the sample, as measured by a thermocouple, is recorded as a function of time using either a potentiometer …
Orthogonal Polynomials, Measures And Recurrence Relations, Joanne Dombrowski, Paul Nevai
Orthogonal Polynomials, Measures And Recurrence Relations, Joanne Dombrowski, Paul Nevai
Mathematics and Statistics Faculty Publications
Properties of measures associated with orthogonal polynomials are investigated in terms of the coefficients of the three term recurrence formula satisfied by the orthogonal polynomials.
L(P) Estimates For Maximal Functions And Hilbert-Transforms Along Flat Convex Curves In R(2), Hasse Carlsson, Michael Christ, Antonio Cordoba, Javier Duoandikoetxea, Jose L. Rudio De Francia, Jim Vance, Stephen Wainger, David Weinberg
L(P) Estimates For Maximal Functions And Hilbert-Transforms Along Flat Convex Curves In R(2), Hasse Carlsson, Michael Christ, Antonio Cordoba, Javier Duoandikoetxea, Jose L. Rudio De Francia, Jim Vance, Stephen Wainger, David Weinberg
Mathematics and Statistics Faculty Publications
No abstract provided.
Summary Abstract - Theoretical And Experimental Capacitance-Voltage Behavior Of Modulation-Doped Al(0.3)Ga(0.7)As/Gaas Heterojunctions, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç
Summary Abstract - Theoretical And Experimental Capacitance-Voltage Behavior Of Modulation-Doped Al(0.3)Ga(0.7)As/Gaas Heterojunctions, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç
Physics Faculty Publications
No abstract provided.
Ar+ In The Terrestrial Ionosphere, Jane L. Fox
Ar+ In The Terrestrial Ionosphere, Jane L. Fox
Physics Faculty Publications
The Ar+ densities in the terrestrial ionosphere are computed for both low and high solar activity models. The reaction N2+(υ > 0) + Ar → N2+ Ar+ is found to be a significant source of Ar+, nearly equal to photoionization and electron impact ionization in the high solar activity model. Peak densities of Ar+ of 11 cm−3 near 190 km and 22 cm−3 near 220 km are predicted for the low and high solar activity models. It is suggested that a simultaneous measurement of Ar+ and Ar densities …
Student Profile, Fall 1985, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Student Profile, Fall 1985, Division Of Student Affairs, Wright State University, Dayton, Ohio, Office Of Student Information Systems, Wright State University
Wright State University Student Fact Books
The student profile fact book has general demographic information on all students enrolled at Wright State University for Fall Quarter, 1985.
Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç
Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç
Physics Faculty Publications
For the first time, we show that the capacitance-voltage behavior of modulation-doped heterojunctions may be accurately described by a first-principles theory that includes selfconsistent quantum two-dimensional (2-D) electron subbands in the GaAs, numerical solution of Poisson's equation for band bending and space charge in the (Al,Ga) As, and series resistance in the 2-D channel and heterointerface. The excellent agreement found between the theory and measurements on selected high-quality Al0.3Ga0.7 As/GaAs heterojunctions allows accurate determination of the maximum 2-D carrier concentration. From this, we find a strong relationship between the conduction-band discontinuity and donor binding energy, giving offsets. …
Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç
Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç
Physics Faculty Publications
Charge carrier mobilities are conveniently measured in simple, homostructure field-effect transistors (FET's) by means of the geometric magnetoresistance (GMR) technique. Heterostructure FET's, however, are more complicated because of multiple conducting regions, as well as multiple conducting bands within a given region. We apply a multilayer GMR mobility model to a frequently used heterostructure FET design, namely, the Al0.3Ga0.7As conduction band. In the particular MODFET structure studied here, the lowest GaAs subband mobility ranges from 5.7X103 cm2/Vs at threshold to 6.9X103 cm2/Vs at saturation while Al0.3Ga0.7As mobility …
Determining The Temperature-Dependent Characteristic Temperature Of Beryllium From Electrical Resistance Measurements, Thomas W. Listerman, Xiao-Li Zhou
Determining The Temperature-Dependent Characteristic Temperature Of Beryllium From Electrical Resistance Measurements, Thomas W. Listerman, Xiao-Li Zhou
Thomas Listerman
We have developed an intermediate-level laboratory experiment to determine the temperature- dependent characteristic temperature of beryllium. The apparatus used to measure the resistance of a beryllium wire sample between liquid nitrogen and room temperatures was simple. The characteristic temperatures obtained from these data using the Block-Grüneisen model are in reasonable agreement with literature values obtained from resistivity and heat capacity experiments. The experiment introduced students to cryogenic and computer data analysis techniques and forced them to extend their knowledge of the theory of electrical resistance and of characteristic temperatures.
Summary Abstract: Capacitance-Voltage Characteristics In Modulation Doped Heterojunction Fets, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç
Summary Abstract: Capacitance-Voltage Characteristics In Modulation Doped Heterojunction Fets, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç
Physics Faculty Publications
No abstract provided.
Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look
Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look
Physics Faculty Publications
The theory for obtaining mobility and carrier concentration profiles by the Hall-effect, magnetoresistance, and capacitance-conductance methods is developed in the relaxation-time approximation. This theory is then applied to semiconductors in which a Schottky barrier is used to control a depletion region. Particular emphasis is given to field-effect transistor structures which are ideally suited for geometric magnetoresistance measurements. A unique feature of the present model is the correction for finite gate (Schottky-barrier) current, which can be very important under forward-gate-bias conditions. The ability to use forward-bias makes the near-surface region more accessible. Also, parasitic resistance effects are treated. We apply these …