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Physics Faculty Research & Creative Works

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Articles 1621 - 1650 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Note On The Van Der Waals Equation, Louis H. Lund Jan 1977

Note On The Van Der Waals Equation, Louis H. Lund

Physics Faculty Research & Creative Works

No abstract provided.

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Final-State Effects In Carbon Auger Spectra Of Transition-Metal Carbides, M. A. Smith, L. L. Levenson Jan 1977

Final-State Effects In Carbon Auger Spectra Of Transition-Metal Carbides, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The carbon Auger spectra of TiC, VC, and Cr3C2 are measured with a resolution of 1.2 eV. Background subtraction is performed, and a deconvolution technique is used to remove energy-dependent broadening from the spectra. An analysis of the data in terms of density-of-states calculations, x-ray emission work, and x-ray photoelectron data shows that final-state effects dominate the Auger spectra. For all of the carbides three peaks are identified as spectral terms resulting directly from final-state hole interactions. Other peaks appearing in the Auger spectra can be identified without final-state considerations. © 1977 The American Physical Society.

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Surface Electromagnetic Waves With Damping. Ii. Anisotropic Media, G. S. Kovener, Ralph William Alexander, I. L. Tyler, Robert John Bell Jan 1977

Surface Electromagnetic Waves With Damping. Ii. Anisotropic Media, G. S. Kovener, Ralph William Alexander, I. L. Tyler, Robert John Bell

Physics Faculty Research & Creative Works

The Technique of Plotting the Attenuated-Total-Reflection (ATR) Reflectance as a Function of Both Frequency and Incident Angle using a Three-Dimensional Plot is Applied to Surface Electromagnetic Waves (SEW) in a Uniaxial Material, MnF2. It is Shown that Dispersion Curves Calculated Without Absorption Do Not Completely Describe the ATR Reflectivity. Experimental Data Confirming the Reflectance Surface Features Are Presented. Also, Additional Minima in the Reflectance Surface Not Associated with SEW Are Discussed. © 1977 the American Physical Society.

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Heisenberg Theory Of Ferromagnetism: Constant Coupling Revisited, Harry A. Brown Jan 1977

Heisenberg Theory Of Ferromagnetism: Constant Coupling Revisited, Harry A. Brown

Physics Faculty Research & Creative Works

The Heinsenberg theory of ferromagnetism has been treated by many types of approximations; one of the more successful is known as constant coupling. The literature constants several different ways of arriving at results like those of the constant-coupling approximation, but proofs that they are indeed equivalent are lacking in some cases. It is shown that two of these methods are equivalent for spin 1/2 and explicitly demonstrated that both yield exactly the constant-coupling results, though simpler in use and concept than the latter. Finally, it is shown that one of the two methods yields the same Curie temperatures as constant …

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Valence-Band Information From The Auger Kvv Spectrum Of Graphite, M. A. Smith, L. L. Levenson Jan 1977

Valence-Band Information From The Auger Kvv Spectrum Of Graphite, M. A. Smith, L. L. Levenson

Physics Faculty Research & Creative Works

The Auger KVV and x-ray photoelectron valence-band spectra of atomically clean, well-ordered graphite are measured. After background subtraction is performed and a deconvolution technique is used to remove energy-dependent features from the Auger data, the transition density function is calculated for the graphite valence band. A comparison is made with other experimental work and with a density-of-states calculation. It is found that the transition density closely resembles the density of states if localized hole effects are considered. © 1977 The American Physical Society.

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Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale Dec 1976

Energy Dependence Of Amorphizing Implant Dose In Silicon, John R. Dennis, Edward Boyd Hale

Physics Faculty Research & Creative Works

The radiation-induced transformation from crystalline to amorphous silicon was studied using ion implantation. The ion energy was varied from 20 to 180 keV for Li+, N+, Ne+, Ar+, and Kr +. The energy dependence of the critical amorphizing dose was determined by electron spin resonance. Comparison of the data with theoretical calculations of the energy density deposited into atomic processes showed good agreement. This energy-dependent agreement gave evidence that energy density is important to the transformation at both low and high implantation temperatures.

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Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton Oct 1976

Excitation Of The N=2 State Of Atomic Hydrogen By Electron Impact In The Distorted-Wave Approximation, Ralph V. Calhoun, Don H. Madison, W. Neil Shelton

Physics Faculty Research & Creative Works

The differential cross sections for excitation of the n=2 state of atomic hydrogen by the impact of electrons with energies of 54, 100, 136, and 200 eV are calculated in the distorted-wave approximation with exchange included. Cross sections for excitation of the 2s1/2, 2p1/2, and 2p3/2 states are calculated and summed to give the n=2 differential cross sections. The results of this calculation are compared with previous theoretical calculations and with recent absolute experimental data.

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Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher Aug 1976

Cross Sections For Excitation Of Atomic Hydrogen To The N=2, 3, And 4 States By 15-200-Kev Protons, John T. Park, Judith E. Aldag, Jacob M. George, Jerry Peacher

Physics Faculty Research & Creative Works

Cross sections for the processes H++H(1 s)H++H*(n = 2, 3, 4) have been extracted from the energy-loss spectra of 15- to 200-keV protons by using a spectrum-fitting technique. Absolute cross sections have been obtained by normalization of the spectra to the theoretical cross section through the use of the Born approximation at 200 keV. The cross-section curves are very similar in shape with maxima at 60 keV. The results have been compared with available theoretical calculations. The n = 2 and n = 3 cross-section measurements are in very good agreement in curve shape with Glauber-approximation …

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Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison Jul 1976

Comparison Of Experimental And Theoretical Electron Ejection Cross Sections In Helium By Proton Impact From 5 To 100 Kev, M. Eugene Rudd, Don H. Madison

Physics Faculty Research & Creative Works

Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential …

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Thomson's Monopoles, I. Adawi Jan 1976

Thomson's Monopoles, I. Adawi

Physics Faculty Research & Creative Works

The angular momentum L of the electromagnetic field due to an electric point charge e, and a magnetic point charge (pole) g, is calculated by several methods to obtain J. J. Thomson's result that L = eg/c, and L is directed along the line joining the electric monopole to the magnetic monopole. The relation to Dirac's monopoles is discussed, and particle size is considered. © 1991, American Association of Physics Teachers. All rights reserved.

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Radiative Lifetimes And Alignment Depolarization Cross Sections For Ybi And Ii By The Hanle Effect In A Flowing Helium System, F. H.K. Rambow, Laird D. Schearer Jan 1976

Radiative Lifetimes And Alignment Depolarization Cross Sections For Ybi And Ii By The Hanle Effect In A Flowing Helium System, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

The radiative lifetimes of the 17992-,25068-,28857-, 37414-, 40564-, and 44017-cm-1 neutral levels and the 30392-cm-1 ion level of Yb have been measured by the Hanle method in a fast-flowing He system. The lifetimes (in units of 10-9 sec) were found to be 820(20), 5.12(0.12), 14.4(0.4), 77.4(6.0), 9.32(0.6), 39.1(3.5), and 5.8(0.6), respectively. In a flowing system with He as a buffer gas the alignment depolarization cross sections with Yb were obtained and are reported here for the first time. They are (in units of 10-15 cm2) 5.0(1.0), 5.9(1.0), 5.9(1.2), 17.9(2.0), 28.2(3.0), 5.16(4.0), and 7.2(2.5), respectively. © 1976 The American Physical Society.

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Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen Jan 1976

Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen

Physics Faculty Research & Creative Works

No abstract provided.

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Surface Electromagnetic Wave Mode And Field Analysis In A Metal-Metal-Oxide-Air System With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell Jan 1976

Surface Electromagnetic Wave Mode And Field Analysis In A Metal-Metal-Oxide-Air System With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

An Explanation is Provided for the Surface Electromagnetic Wave (SEW) Energy Ejection from a Thin Film at the Longitudinal and Transverse Optical-Phonon Frequencies of the Film Material. Field Ratio Calculations Identify Previously Discussed Metal-Metal-Oxide-Air SEW Modes as Those Expected from the Berreman Configuration, and It is Shown that Greenler Technique High-Incidence-Angle-Reflectance Data on the Same System May Be Similarly Interpreted. © 1976 the American Physical Society.

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The Magnification Factor For Sodium Chloride Liesegang Circles Established With An Aerosol Centrifuge, O. Preining, Josef Podzimek, P. Yue Jan 1976

The Magnification Factor For Sodium Chloride Liesegang Circles Established With An Aerosol Centrifuge, O. Preining, Josef Podzimek, P. Yue

Physics Faculty Research & Creative Works

Sodium chloride particles deposited on a gelatin film containing silver nitrate form in a humid environment clearly visible dark brown reaction spots (Liesegang circles) after development in u.v.-light. The size of these reaction spots depends on the mass of NaCl in the particles. To establish the spot size vs particle size relation, particles produced by nebulising NaCl-solutions and sea water were sampled in an aerosol centrifuge. The location of deposition yields the aerodynamic diameter of the particle, and the spot size is measured microscopically. In this way the spot size vs aerodynamic diameter relation is established experimentally in the so …

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Surface Electromagnetic Waves With Damping. I. Isotropic Media, G. S. Kovener, Ralph William Alexander, Robert John Bell Jan 1976

Surface Electromagnetic Waves With Damping. I. Isotropic Media, G. S. Kovener, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

Surface-Electromagnetic-Wave Dispersion Curves Are Usually Calculated using a Simple Equation Derived from Maxwell's Equations and Boundary Conditions. When Complex Dielectric Functions Are Used for the Two Media, the Component of the Propagation Vector Along the Surface, Kx, Becomes Infinite as the Frequency Approaches the Surface Polariton Frequency Ωs If Ω is Considered Complex and Kx is Real. on the Other Hand, If Kx is Considered Complex and Ω Real, the Dispersion Curves Bend Back Toward Smaller Kx as Ω Approaches Ωs. We Have Previously Demonstrated that Both Types of Behavior Can Be Obtained from Attenuated-Total-Reflection Measurements of Silver. We Now …

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Absorption In The Infrared Of Surface Electromagnetic Waves By Adsorbed Molecules On A Copper Surface, K. Bhasin, D. Bryan, Ralph William Alexander, Robert John Bell Jan 1976

Absorption In The Infrared Of Surface Electromagnetic Waves By Adsorbed Molecules On A Copper Surface, K. Bhasin, D. Bryan, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

Experimental Observations Have Been Made for the First Time that Surface Electromagnetic Wave (SEW) Spectroscopy Can Be Used to Measure the Infrared Spectra of Adsorbed Molecules and Very Thin Films on Metal Surfaces. using a Tunable CO2 Laser (9.2-10.8 Μm Wavelength), the 975 and the 1037 Cm-1 Resonances of 5-25 Å Thick Physiosorbed Benzene on Copper Were Observed. Broadening of These Resonances for the Thinnest Layers of Benzene Was Observed. Also SEW Spectroscopy and Ellipsometry Were Used to Study Thin Films of Cellulose Acetate (15-75 Å) on Copper. Further, It Was Shown that Film Thicknesses Determined by SEW Spectroscopy Are …

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Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer Jan 1976

Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

Radiative lifetimes of the first P322 state of Mgu, Cau, Znu, Sru, Cdu, and Bau are reported as measured by the Hanle effect in a fast-flowing helium afterglow. They are, respectively, 3.65(0.12), 6.61(0.30), 2.4(0.3), 6.64(0.10), 2.86(0.25), 6.78(0.40) in units of 10-9 sec. The ions in the afterglow are created by Penning ionization of the neutral metal atoms, thus providing a steady-state, field-free region for observation. Comparisons are made with measurements by other methods, and discrepancies are discussed. © 1976 The American Physical Society.

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Note On Amorphous Magnetic Materials, Louis H. Lund Jan 1976

Note On Amorphous Magnetic Materials, Louis H. Lund

Physics Faculty Research & Creative Works

No abstract provided.

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Saturation Effects In A Tunable Coherent Near-Infrared Source, Israel L. Tyler, R. (Ralph) W. Alexander, R. (Robert) J. (John) Bell Dec 1975

Saturation Effects In A Tunable Coherent Near-Infrared Source, Israel L. Tyler, R. (Ralph) W. Alexander, R. (Robert) J. (John) Bell

Physics Faculty Research & Creative Works

A Saturation Effect in a Tunable Infrared Source Utilizing Four-Wave Parametric Conversion in Potassium Vapor is Reported and is Shown to Be the Result of Parasitic Oscillations. a Hundredfold Increase over Previously Attained Power Levels Has Been Affected Via Elimination of These Oscillations.

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Radiative Lifetime Of The B ²Σˉ State Of Ch, Richard A. Anderson, Jerry Peacher, David M. Wilcox Dec 1975

Radiative Lifetime Of The B ²Σˉ State Of Ch, Richard A. Anderson, Jerry Peacher, David M. Wilcox

Physics Faculty Research & Creative Works

The radiative lifetimes of the N'=3 to 15 rotational states of the v'=0 level of the B 2Σ- state of CH were measured. Emission lines were observed to N'=15, but no lines above this rotational state were observed. This result agrees with previous studies. The lifetimes of all rotational states were between 300 and 400 ns. Previous measurements have indicated that the N'=15 level might have a lifetime as short as 100 ns.

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High-Frequency Dielectric Measurements On Electro-Optic Single Crystals, J. R. Teague, R. R. Rice, Robert Gerson Dec 1975

High-Frequency Dielectric Measurements On Electro-Optic Single Crystals, J. R. Teague, R. R. Rice, Robert Gerson

Physics Faculty Research & Creative Works

A slotted line was used to measure the high-frequency dielectric constant and loss tangent of several electro-optic crystals useful for wide-band laser modulator applications. Dielectric measurements were made at 0.1, 0.3, 1.0, and 2.0 GHz.

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Intrinsic Viscosity Of Stiff Dumbbells From Time Correlation Functions, Gerald Wilemski Sep 1975

Intrinsic Viscosity Of Stiff Dumbbells From Time Correlation Functions, Gerald Wilemski

Physics Faculty Research & Creative Works

The intrinsic viscosity of a suspension of stiff dumbbells is evaluated by a time correlation function method. The required moments of the internal coordinates are calculated directly from the diffusion equation, without explicit evaluation of the Green's function. For the rigid dumbbell, the correct high frequency limit is obtained, disposing of recent doubts over this possibility. The interplay of dumbbell stiffness and shearing frequency is also illustrated.

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Energy And Angular Distribution Of Electrons Ejected From Helium By Fast Protons And Electrons: Theory And Experiment, Steven Trent Manson, Larry H. Toburen, Don H. Madison, Nikolaus Stolterfoht Jul 1975

Energy And Angular Distribution Of Electrons Ejected From Helium By Fast Protons And Electrons: Theory And Experiment, Steven Trent Manson, Larry H. Toburen, Don H. Madison, Nikolaus Stolterfoht

Physics Faculty Research & Creative Works

A comprehensive study of the angular and energy distributions of electrons ejected in collisions of fast electrons and protons with He is presented. New experimental results for 300-keV, 1-MeV, and 5-MeV proton impact are reported along with theoretical results for 2-keV electron impact and 100-keV, 300-keV, 1-MeV, and 5-MeV proton impact. The theoretical results, based upon Born approximation with Hartree-Slater initial discrete and final continuum wave functions, show excellent agreement with experimental electron-impact results. Serious discrepancies are found between theory and experiment in the angular distribution of ejected electrons for forward angles for 100- and 300-keV proton impact; the discrepancies …

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Some Comments On Correlation-Function Formulas For Polymer Intrinsic Viscosity, Walter H. Stockmayer, Gerald Wilemski, Hiromi Yamakawa, Genzo Tanaka Jul 1975

Some Comments On Correlation-Function Formulas For Polymer Intrinsic Viscosity, Walter H. Stockmayer, Gerald Wilemski, Hiromi Yamakawa, Genzo Tanaka

Physics Faculty Research & Creative Works

No abstract provided.

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Binary Nucleation. Ii. Time Lags, Gerald Wilemski May 1975

Binary Nucleation. Ii. Time Lags, Gerald Wilemski

Physics Faculty Research & Creative Works

The role of the time lag needed to attain steady state nucleation in binary vapors is discussed. Under appropriate conditions it is possible to obtain both a large predicted rate of binary nucleation and a large time lag. In this circumstance, homogeneous nucleation of the more concentrated component may be the predominant process. It is of obvious importance to the experimentalist to differentiate between these possibilities. Approximate formulas for the time lags are developed, and representative calculations for the ethanol-water system are reported.

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Binary Nucleation. I. Theory Applied To Water-Ethanol Vapors, Gerald Wilemski May 1975

Binary Nucleation. I. Theory Applied To Water-Ethanol Vapors, Gerald Wilemski

Physics Faculty Research & Creative Works

A quantitative study of nucleation in vapor mixtures of ethanol and water near 273°C is presented. First, Reiss' theory of binary nucleation is reexamined. The theory is modified slightly in order to yield the proper limit for homogeneous nucleation in a one-component system. Moreover, a corrected expression for the equilibrium concentration of mixed clusters is derived. Calculations of the critical vapor activities needed to produce a visible condensate are presented and compared with the results of Flood's cloud chamber experiments. The agreement is only fair, but qualitative accord is found.

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Differential Cross Sections For Elastic And Inelastic Scattering Of 15-100-Kev Li⁺ By He, John T. Park, Victor Pol, James E. Lawler, Jacob M. George, Judith E. Aldag, John W. Parker, Jerry Peacher Mar 1975

Differential Cross Sections For Elastic And Inelastic Scattering Of 15-100-Kev Li⁺ By He, John T. Park, Victor Pol, James E. Lawler, Jacob M. George, Judith E. Aldag, John W. Parker, Jerry Peacher

Physics Faculty Research & Creative Works

Sets of energy-loss spectra for Li+ incident on He that were taken at a series of scattering angles were used to calculate differential cross sections. Differential cross sections are given for elastic scattering and for excitation of the He (n=2) states. The differential cross section is also given for excitation of states corresponding to a 60-eV energy loss. These inelastic differential cross sections exhibit maxima at scattering angles greater than zero. The velocity dependence of the cross sections can be compensated by displaying the elastic data in ρ-vs-τ plots and the inelastic data in ρ-vs-E3/2θ plots. When …

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Electron Impact Autoionization In Heavy Alkali Metals, Kaare J. Nygaard Jan 1975

Electron Impact Autoionization In Heavy Alkali Metals, Kaare J. Nygaard

Physics Faculty Research & Creative Works

Autoionizing levels in cesium, rubidium, and potassium have been studied by electron impact in a crossed-beam apparatus. Comparisons are made with the binary-encounter calculations of Roy and Rai. The effects of autoionization and inner-shell ionization have been overestimated in the theory. © 1975 The American Physical Society.

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Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin Jan 1975

Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin

Physics Faculty Research & Creative Works

The relative photoionization cross sections for cesium atoms selectively excited to the 6P32,122 states have been measured in a triple-crossed-beam experiment. A cesium discharge lamp produced resonant wavelengths of 8521 and 8944 for the excitation process. A Hg-Xe lamp combined with a grating monochromator was used for the actual ionization in the wavelength region from 2500 to 5000. Background counts due to photoionization of ground-state cesium atoms and dimers as well as various surface effects were discriminated against by chopping the excitation light source. The data are compared with results from radiative-recombination measurements in which the fine-structure levels are not …

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Strain Effects On The Esr Spectrum From Antimony Donors In Germanium, Edward Boyd Hale, John R. Dennis, Shih Hua Pan Jan 1975

Strain Effects On The Esr Spectrum From Antimony Donors In Germanium, Edward Boyd Hale, John R. Dennis, Shih Hua Pan

Physics Faculty Research & Creative Works

The electron-spin-resonance spectra from surface-strained (but not externally stressed) antimony-doped germanium are investigated in detail. Experimental data are given for the linewidth, line asymmetry, and line-shape reversal feature as well as for the changes in donor concentration, temperature, and surface conditions. The donors of interest occur in a surface layer several microns thick. A theoretical analysis is based on the Kohn-Luttinger formulation for a shallow donor electron, which is forced by surface strain to predominately occupy a [111] conduction-band valley minimum. A substantial distribution in strain among the donor sites is necessary to account for the line-structure features. These features …

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