Open Access. Powered by Scholars. Published by Universities.®

Physics Commons™

Open Access. Powered by Scholars. Published by Universities.®

PDF

1990

Discipline
Institution
Keyword
Publication
Publication Type

Articles 31 - 60 of 193

Full-Text Articles in Physics

Laser-Induced Detachment Processes In An Electric Field, Bo Gao, Anthony F. Starace Nov 1990

Laser-Induced Detachment Processes In An Electric Field, Bo Gao, Anthony F. Starace

Anthony F. Starace Publications

An analytic momentum-space wave function for an electron in both laser and static uniform electric fields is presented. It is used to obtain analytic multiphoton detachment cross sections in a static, uniform electric field which include effects of static-field-induced electron-photon interactions. These general results are not restricted to weak laser intensities or to weak static-field strengths and depend only on (a) the electric dipole approximation and (b) the approximation that final-state electron-atom interactions are ignored. Four specific predictions of our general formulas for the most interesting case of linearly polarized light polarized along the static-field direction are presented for weakly …

Go to article

Using Refraction Caustics To Monitor Evaporation Of Liquid Drop Lenses, James A. Lock, Jearl D. Walker, James H. Andrews Nov 1990

Using Refraction Caustics To Monitor Evaporation Of Liquid Drop Lenses, James A. Lock, Jearl D. Walker, James H. Andrews

Physics Faculty Publications

Irregularities in the perimeter of a water droplet adhering to a vertical pane of glass cause perturbations in the curvature of the droplet surface. When laser light passes through such a droplet, the perturbations produce a far field refraction caustic, which is a section of the caustic known as the parabolic umbilic in the catastrophe theory classification. As the water evaporates and the droplet surface curvature changes, the section of the parabolic umbilic caustic on the viewing screen also changes. We determine the evolution of curvature of the droplet surface by observing the evolution of the far field caustic and …

Go to article

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz Oct 1990

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz

Peer Reviewed Articles

Vibrational and rotational distributions of CO excited by collisions with 2.3 eV H atoms have been obtained by monitoring the products with vacuum ultraviolet (VUV) laser induced fluorescence. Translational-to-vibrational (T→V) transfer is dominated by the dynamics of collisions occurring in the two wells on the H+CO potential energy surface, one characterizing the HCO radical and the other characterizing COH. The measured vibrational distributions agree well with the results of trajectory calculations performed on the ab initio potential energy surface of Bowman, Bittman, and Harding (BBH). The measured rotational distributions show two significant differences from the calculated ones. First, for v …

Go to article

Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang Oct 1990

Heterotic Conformal Field Theory And Gepner’S Construction, Darwin Chang, Asim Gangopadhyaya, Alok Kumar, Jin Wang

Physics: Faculty Publications and Other Works

We discuss some general properties of heterotic conformal field theory in which conformal anomalies c are different for the left-moving and right-moving sectors. It is precisely this type of theory that can be applied immediately to the construction of heterotic string theory. We discuss a general way of constructing such a theory using free fermions. The construction is then applied to generalize Gepner's construction of superstring solutions using the tensor products of N=2 superconformal field theories.

Go to article

Theoretical Description Of The Binary Peak In Clothed Ion-Atom Collisions, C. O. Reinhold, Ronald E. Olson Oct 1990

Theoretical Description Of The Binary Peak In Clothed Ion-Atom Collisions, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

The impulse or binary encounter approximation for ion-atom collisions is extended to treat the non-Coulomb interaction between a clothed projectile ion and the target electrons. This model is shown to reproduce the unexplained enhancement of the zero-degree binary peak for partially stripped ions over that for Equi velocity fully stripped ions that has recently been observed experimentally in Fq++H2, He collisions. Very good agreement is obtained between theory and experiment and, furthermore, this model is used to illuminate the underlying dynamics which leads to the observed enhancement. © 1990 IOP Publishing Ltd.

Go to article

A Loading Device For Fracture Testing Of Compact Tension Specimens In The Scanning Electron Microscope, Jügen Rödel, James F. Kelly, Mark R. Stoudt, Stephen J. Bennison Oct 1990

A Loading Device For Fracture Testing Of Compact Tension Specimens In The Scanning Electron Microscope, Jügen Rödel, James F. Kelly, Mark R. Stoudt, Stephen J. Bennison

Scanning Microscopy

A loading device for performing fracture experiments on compact tension specimens in the SEM has been designed. Its key elements are a piezoelectric translator for applying controlled displacements to the loading points on the specimen and a load cell to measure applied loads. The effective transmission of displacement from the piezoelectric driver to the specimen was found to be the major mechanical design problem. The peripheral equipment includes a function generator and a high voltage amplifier that drives the piezoelectric translator as well as a video overlay and standard video equipment to record the image continuously during the course of …

Go to article

Angular Distribution Of Auger Electrons Emitted Through The Resonant Transfer And Excitation Process Following O⁵⁺+He Collisions, Malika Benhenni, Stephen M. Shafroth, J. K. Swenson, Michael Schulz, J. P. Giese, Harald Schone, Charles Randy Vane, Peter F. Dittner, Sheldon Datz Oct 1990

Angular Distribution Of Auger Electrons Emitted Through The Resonant Transfer And Excitation Process Following O⁵⁺+He Collisions, Malika Benhenni, Stephen M. Shafroth, J. K. Swenson, Michael Schulz, J. P. Giese, Harald Schone, Charles Randy Vane, Peter F. Dittner, Sheldon Datz

Physics Faculty Research & Creative Works

This Letter reports the first measurements of the angular distribution of Auger electrons emitted from the decay of the (1s2s2p2)3D O4+** doubly excited state formed predominantly through resonant transfer and excitation (RTE) in collisions of 13-MeV O5+ projectiles with He. The (1s2s2p2)3D angular distribution is strongly peaked along the beam direction, in agreement with recent calculations of the RTE angle-dependent impulse approximation. Furthermore, interference effects between the RTE and the elastic target direct-ionization channels are observed.

Go to article

Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou Oct 1990

Mossbauer Spectroscopy Of Fe2+ Binding To Apo And Holo Mammalian Ferritin, Richard B. Frankel, Gerald D. Watt, Georgia C. Papaefthymiou

Physics

The anaerobic binding of Fe2+ to apo and holo Mammalian ferritin has been studied in the pH range from 6.0 to 10.0. Mossbauer spectroscopy of samples in which the added Fe 2+ is enriched in Fe-57 shows that the Fe2+ ions bind to the ferritin core and exchange electrons with Fe3+ ions in the core.

Go to article

Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii Oct 1990

Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii

Physics

The rapid rise in resistance occurring in barely conducting quench-condensed Pb films cooled through temperatures characteristic of the bulk superconducting transition is found to be strongly current dependent, the resistance increasing rapidly with decreasing current and temperature. Annealing the same film at temperatures below 40 K changes the behavior to that of a conventional superconductor with resistance that drops as the film current and temperature decrease. Experimental evidence suggests this results from a transition from quasiparticle-dominated to Josephson-dominated tunneling.

Go to article

Nonalloyed Ohmic Contacts On Low-Temperature Molecular-Beam Epitaxial Gaas: Influence Of Deep Donor Band, H. Yamamoto, Z-Q. Fang, David C. Look Oct 1990

Nonalloyed Ohmic Contacts On Low-Temperature Molecular-Beam Epitaxial Gaas: Influence Of Deep Donor Band, H. Yamamoto, Z-Q. Fang, David C. Look

Physics Faculty Publications

The Ohmic nature of the nonalloyed metal contact on molecular beam epitaxial GaAs grown at 200 °C was studied. The specific contact resistances at room temperature and 120 K were 1.5×10−3 and 7.0×10−1 Ω cm2, respectively. These values are anomalously low considering that the conduction‐band electron concentration in this material is less than 1011 cm−3 at room temperature. The experimental results indicate that the carrier transport at the metal/semiconductor interface is dominated by a dense (∼3×1019 cm−3) EL2‐like deep donor band, rather than the usual conduction band.

Go to article

Quantum-Mechanical Harmonic Chain Attached To Heat Baths Ii: Nonequilibrium Properties, Ulrich Zürcher, Peter Talkner Oct 1990

Quantum-Mechanical Harmonic Chain Attached To Heat Baths Ii: Nonequilibrium Properties, Ulrich Zürcher, Peter Talkner

Physics Faculty Publications

We study nonequilibrium properties of a one-dimensional harmonic chain to whose ends independent heat baths are attached which are kept at different temperatures. Using the quantum Langevin equation approach, we determine the stationary nonequilibrium state for arbitrary temperatures and coupling strength to the heat baths. This allows us to discuss several typical nonequilibrium properties. We find that the heat flux through the chain is finite as the length of the chain goes to infinity, i.e., we recover the well-known fact that the lattice thermal conductivity of the perfect harmonic chain is infinite. In the quantal case, the heat flux jqm …

Go to article

Gravitational Synchrotron Radiation From Cosmic Strings, Alan Cresswell, Robert L. Zimmerman Oct 1990

Gravitational Synchrotron Radiation From Cosmic Strings, Alan Cresswell, Robert L. Zimmerman

Physics Faculty Publications and Presentations

This work studies the gravitational synchrotron radiation emitted from arbitrary cusps of cosmic strings. The results are expressed in terms of four parameters describing the motion of such a cusp. The power spectrum is derived for cusps moving at unit velocity. By using a phenomenological approach the authors also derive the power emitted when the radiation reaction on the cusps is taken into account. In both cases, the synchrotron nature of the radiation produces a power spectrum emitted in a narrow forward cone. If cosmic strings do exist, the radiation emitted by their cusps would seem to be a potential …

Go to article

The Effect Of Externally Applied Oscillating Electric Fields On The L=1 And L=2 Diocotron Modes In Non-Neutral Plasmas, Ross L. Spencer Oct 1990

The Effect Of Externally Applied Oscillating Electric Fields On The L=1 And L=2 Diocotron Modes In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

A high-frequency oscillating electric field can change the properties of diocotron modes in non-neutral plasmas. The effect depends crucially on the azimuthal mode number, m, of the applied field. For m=0, plus or minus 1 there is no effect, and for applied standing waves there is also no effect. But if the applied field has the form of a traveling wave with the norm of m greater than or equal to 2, the frequency of stable diocotron modes can be modified and for the norm of m greater than or equal to 3, the l=2 instability of hollow density profiles …

Go to article

Deposition Of Boron-Containing Films From Decaborane, James T. Spencer, Peter A. Dowben, Yoon G. Kim Sep 1990

Deposition Of Boron-Containing Films From Decaborane, James T. Spencer, Peter A. Dowben, Yoon G. Kim

Peter Dowben Publications

Depopsition of a boron nitride film is carried out by introducing decaborane and dry nitrogen or ammonia into a plasma-assisted chemical vapor deposition chamber. The nitrogen or ammonia partial pressure should provide an excess over the decarborane pressures for example 200 milliTorr of N2 or NH3 and 50 MilliTorr of B10H14. Other film layers can also be produced starting from decaborane.

Go to article

Computer Simulation Study Of Conductivity In A 2-Dimensional Binary Fluid Mixture, Ras B. Pandey Sep 1990

Computer Simulation Study Of Conductivity In A 2-Dimensional Binary Fluid Mixture, Ras B. Pandey

Faculty Publications

A computer-simulation model is introduced to study the transport properties of a binary fluid mixture in which the constituents of one fluid (the tracer particles) carry charges in a linear charge-density gradient in the background charge of the second fluid. In the steady-state equilibrium, an effective conductivity σc(p,r) is estimated as a function of the carrier concentration p and the range of interactions r. The conductivity is observed to vary nonmonotonically with the concentration p, and it exhibits a maximum at a characteristic value pc. The conductivity decreases when the …

Go to article

The Long-Period Field Rr Lyrae Stars, Edward G. Schmidt, Charles G. Loomis, Andrew T. Groebner, Chris T. Potter Sep 1990

The Long-Period Field Rr Lyrae Stars, Edward G. Schmidt, Charles G. Loomis, Andrew T. Groebner, Chris T. Potter

Edward Schmidt Publications

VR light curve3 have been obtained for 16 faint variable stars with periods shorter than 1 day. Although, as expected, most of the light curves are typical of Bailey-type ab RR Lyrae stars, some have slower rises to maximum and flatter tops. Fourier decomposition was performed to further explore these trends. Combining these data with previously published Fourier decompositions of RR Lyrae light curves, we find that the Fourier coefficients are essentially constant for periods shorter than three-quarters of a day for Bailey-type ab RR Lyrae stars but that the amplitude ratios, R (12), R (13), and R (14), decrease …

Go to article

Theory Of Compositional And Magnetic Correlations In Alloys: Interpretation Of A Diffuse Neutron-Scattering Experiment On An Iron-Vanadium Single Crystal, J. B. Staunton, Duane D. Johnson, F. J. Pinski Sep 1990

Theory Of Compositional And Magnetic Correlations In Alloys: Interpretation Of A Diffuse Neutron-Scattering Experiment On An Iron-Vanadium Single Crystal, J. B. Staunton, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

We describe a first-principles theory for compositional and magnetic correlations in alloys and compare the results of the theory with recent diffuse, unpolarized, neutron-scattering measurements on a single crystal of ferromagnetic Fe0.865V0.135. The nuclear cross section is described very well by the theory and we are able to connect the q-dependent structure to the underlying electronic structure of the alloy. The magnetocompositional and magnetic correlations also may be obtained for comparison to polarized measurements.

Go to article

Review Of Verification And Compliance: A Problem Solving Approach By Michael Krepon & Mary Umberger, Toward A Comprehensive Test Ban By Steve Fetter, And Making Space Defense Work: Must The Superpowers Cooperate? By A. Fenner Milton, M. Scott Davis, & John Parmentola, David W. Hafemeister Sep 1990

Review Of Verification And Compliance: A Problem Solving Approach By Michael Krepon & Mary Umberger, Toward A Comprehensive Test Ban By Steve Fetter, And Making Space Defense Work: Must The Superpowers Cooperate? By A. Fenner Milton, M. Scott Davis, & John Parmentola, David W. Hafemeister

Physics

No abstract provided.

Go to article

Radiosensitivity Parameters For Cell Survival In Tradescantia And For Chromosome Aberrations In Chinese Hamster Cells, Robert Katz, G. Huang Sep 1990

Radiosensitivity Parameters For Cell Survival In Tradescantia And For Chromosome Aberrations In Chinese Hamster Cells, Robert Katz, G. Huang

Robert Katz Publications

Data for the loss of reproductive integrity of Tradescantia stamen hairs irradiated with 250 keV X rays and 0.43 and 5.6 MeV neutrons are fitted with radiosensitivity parameters from track theory, with E0 and m from X-ray data while σ0 and κ are then found from neutron irradiations. The X-ray data display a clear shoulder with 100% survival below 0.18 Gy and a “linear tail.” Data for abnormal metaphases and chromatid exchanges in Chinese Hamster cells have also been fitted with parameters. Parameters for abnormal metaphases are nearly identical with those obtained years ago for cell killing from …

Go to article

High-Velocity Molecular Gas Associated With Cold Iras Sources, Bruce Wilking, James Blackwell, Lee Mundy Sep 1990

High-Velocity Molecular Gas Associated With Cold Iras Sources, Bruce Wilking, James Blackwell, Lee Mundy

Physics Faculty Works

Maps are presented in the J = 2-1 transition of CO for five molecular outflows associated with deeply embedded far-infrared sources. All of the outflows display lobes of both red- and blue-shifted gas with full velocity extents ranging from 37 to 63 km/s. At least two of the outflows are bipolar but neither is well-collimated. High-velocity C-13O emission is detected in all sources. The data are used to estimate the optical depths, excitation temperatures, masses, momentum supply rates, and energy supply rates for the outflows. A comparison between the properties of IRAS-selected and optically selected molecular outflows is made. The …

Go to article

Doubly Differential Detachment Cross Sections For Fast H-–Rare-Gas Collisions, Chih-Ray Liu, Anthony F. Starace Sep 1990

Doubly Differential Detachment Cross Sections For Fast H-–Rare-Gas Collisions, Chih-Ray Liu, Anthony F. Starace

Anthony F. Starace Publications

Detailed theoretical analyses are presented of the projectile-energy dependence as well as the target dependence of the electron-detachment collision processes, H-+T→H(n=2)+T*+e-. These analyses are illustrated by calculations of both projectile-frame and laboratory-frame doubly differential cross sections (DDCS’s) for 0.5-, 1.0-, and 1.5-MeV H- collisions with He targets and for 0.5-MeV H- collisions with Ne, Ar, Kr, and Xe targets; in addition, we present laboratory frame DDCS’s for 0.1-MeV H- collisions with Xe targets. Comparisons with available experimental data are given.

Go to article

Two New Short-Period Cepheids, Edward G. Schmidt, Bradley A. Gross Sep 1990

Two New Short-Period Cepheids, Edward G. Schmidt, Bradley A. Gross

Edward Schmidt Publications

The General Catalogue of Variable Stars gives periods of slightly less than three-quarters of a day for the stars NO Cas and CN Tau. However, new photometry demonstrates that their periods are actually 2.6 and 1.8 days, respectively, and they are thus classical Cepheids. Fourier decompositions of their light curves are performed, and they are found to be members of a class of Cepheids with periods less than three days which may be related to the s-Cepheids. These two stars represent the shortest and longest known members of this class and thus are very useful in defining its properties in …

Go to article

Quantum-Mechanical Harmonic Chain Attached To Heat Baths I: Equilibrium Properties, Ulrich Zürcher, Peter Talkner Sep 1990

Quantum-Mechanical Harmonic Chain Attached To Heat Baths I: Equilibrium Properties, Ulrich Zürcher, Peter Talkner

Physics Faculty Publications

Starting from quantum Langevin equations for operators we study thermal properties of a one-dimensional harmonic chain to whose ends independent heat baths are attached. In this paper, we mainly discuss the thermal equilibrium state that the chain eventually approaches if the heat baths are at equal temperatures. In the classical limit, this state is determined by the Gibbs ensemble of the free chain, whereas in the quantal case, this is only true if the strength of coupling between chain and heat baths is made infinitely small. We find that corrections for finite coupling strength are appreciable only in boundary layers …

Go to article

Evidence For A Crossover From Multiple Trapping To Percolation In The High-Temperature Electrical Conductivity Of Mn-Doped Lacroo₃, Ryne P. Raffaelle, Harlan U. Anderson, Don M. Sparlin, Paul Ernest Parris Sep 1990

Evidence For A Crossover From Multiple Trapping To Percolation In The High-Temperature Electrical Conductivity Of Mn-Doped Lacroo₃, Ryne P. Raffaelle, Harlan U. Anderson, Don M. Sparlin, Paul Ernest Parris

Materials Science and Engineering Faculty Research & Creative Works

We explain the deep electrical conductivity minimum near x=0.05 in the perovskite-type ceramic LaCr1-xMnxO3 as a crossover between two different regimes of hopping conduction. At low Mn concentrations the diffusion of small polarons among Cr ions is limited by multiple trapping at energetically lower Mn sites. At higher concentrations a percolating path of Mn sites forms and direct transport between Mn ions dominates the conduction process.

Go to article

Theory Of Light Scattering By A Nonequilibrium Binary Mixture, J.C. Nieuwoudt, B.M. Law Aug 1990

Theory Of Light Scattering By A Nonequilibrium Binary Mixture, J.C. Nieuwoudt, B.M. Law

Faculty Publications

A binary mixture subject to a large temperature gradient is studied. Solutions of the evolution equations for the time-dependent fluctuation correlations are obtained using mode-coupling theory subject to the assumption that the mixture is not close to a critical point. From these results predictions for the light-scattering spectrum at the Rayleigh and Brillouin lines are made. The temperature gradient is shown to cause a large enhancement of the scattering amplitude at the Rayleigh line, whereas the effect at the Brillouin line is found to be small.

Go to article

Possible Conserved Quantity For The Henon-Heiles Problem, Paul Finkler, C. Edward Jones, Glenn A. Sowell Aug 1990

Possible Conserved Quantity For The Henon-Heiles Problem, Paul Finkler, C. Edward Jones, Glenn A. Sowell

Paul Finkler Papers

We study a power-series expansion for a conserved quantity K in the case of the two-dimensional Henon-Heiles potential. An alternative technique to that of Gustavson [Astron. J. 71, 670 (1966)] is applied to find the coefficients in the expansion for K. The technique is used to determine twelve orders for the conserved quantity K, more than twice as many as that calculated by Gustavson. We investigate the degree of constancy of our truncated K in regions where the motion is known to be chaotic and also where it is nonchaotic.

Go to article

Intracavity Frequency Doubling Of A Nd:Yag Laser With An Organic Nonlinear Optical Crystal, Stephen Ducharme, W.P. Risk, W.E. Moerner, Victor Y. Lee, R.J. Twieg, G.C. Bjorklund Aug 1990

Intracavity Frequency Doubling Of A Nd:Yag Laser With An Organic Nonlinear Optical Crystal, Stephen Ducharme, W.P. Risk, W.E. Moerner, Victor Y. Lee, R.J. Twieg, G.C. Bjorklund

Stephen Ducharme Publications

Your access to Appl. Phys. Lett. is provided through the subscription of Univ Nebraska-Lincoln Lib. What is this? Scitation Citing Articles | CrossRef Citing Articles | All Citing Articles [ Previous / Next Abstract | Issue Table of Contents | Bottom of Page ] Applied Physics Letters -- August 6, 1990 -- Volume 57, Issue 6, pp. 537-539 Full Text: [ PDF (639 kB) ] Order Rightslink Permissions for Reuse About Rightslink view MyArticles What is this? Select up to 20 articles at a time. Intracavity frequency doubling of a Nd:YAG laser with an organic nonlinear optical crystal Stephen Ducharme, …

Go to article

Magnetic Polarity Fractions In Magnetotactic Bacterial Populations Near The Geomagnetic Equator, F. F. Torres De Araujo, F. A. Germano, L. L. Goncalves, M. A. Pires, Richard B. Frankel Aug 1990

Magnetic Polarity Fractions In Magnetotactic Bacterial Populations Near The Geomagnetic Equator, F. F. Torres De Araujo, F. A. Germano, L. L. Goncalves, M. A. Pires, Richard B. Frankel

Physics

The relative numbers of North-seeking and South-seeking polarity types in natural populations of magnetotactic bacteria were determined at sites on the coast of Brazil. These sites were South of the geomagnetic equator and had upward geomagnetic inclinations of 1–12°. For upward inclinations >6°, South-seeking cells predominated over North-seeking cells by more than a factor of 10. For upward inclinations

Go to article

Analytic Solutions For Three-State Systems With Overlapping Pulses, C. E. Carroll, Foek T. Hioe Aug 1990

Analytic Solutions For Three-State Systems With Overlapping Pulses, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

Two classes of analytic solutions for three-state systems involving two overlapping laser pulses of different shapes, or of similar shapes but with their centers displaced, are presented. We find a remarkable connection between the order of arrival of the two overlapping pulses and the effectiveness of transfer from the ground state to the third state, and we find remarkable results for the maximum occupation probability of the intermediate state. The approach of these analytic solutions to the adiabatic-following process is also demonstrated.

Go to article

Anomalous Hall-Effect Results In Low-Temperature Molecular-Beam-Epitaxial Gaas - Hopping In A Dense El2-Like Band, David C. Look, D. C. Walters, M. O. Manasreh, J. R. Sizelove, C. E. Stutz, K. R. Evans Aug 1990

Anomalous Hall-Effect Results In Low-Temperature Molecular-Beam-Epitaxial Gaas - Hopping In A Dense El2-Like Band, David C. Look, D. C. Walters, M. O. Manasreh, J. R. Sizelove, C. E. Stutz, K. R. Evans

Physics Faculty Publications

Molecular-beam-epitaxial GaAs grown at very low temperatures (∼200 °C) exhibits anomalous Hall-effect properties. Here we show conclusively that the room-temperature conduction is due to activated (nearest-neighbor) hopping in a deep defect band of concentration 3×1019 cm-3, and energy Ec-0.75 eV, along with conduction due to free carriers thermally excited from this band. At low measurement temperatures, variable-range hopping [σ∝exp(-T0/T)1/4] prevails. The conduction-band mobility can be well explained by neutral-deep-donor scattering in parallel with lattice scattering.

Go to article

First Prev Next Last