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Full-Text Articles in Physics

Model For Chaotic Dynamics Of The Perpendicular-Pumping Spin-Wave Instability, S. M. Rezende, O. F. De Alcantara Bonfim, F. M. De Aguiar Apr 1986

Model For Chaotic Dynamics Of The Perpendicular-Pumping Spin-Wave Instability, S. M. Rezende, O. F. De Alcantara Bonfim, F. M. De Aguiar

Physics Faculty Publications and Presentations

We propose a model for the dynamics of spin-wave instabilities driven by a rf field perpendicular to the dc magnetic field in the second- order Suhl process. We show that a self-oscillation arises from the dynamic nonlinear interaction between the k=0 mode driven by the pumping field and a degenerate k≠0 magnon, with frequency that depends on the dissipation rates and the nonlinear interaction parameters and not on the sample dimensions. For certain parameter values, as the driving field increases we find a period-doubling route to chaos and odd-period bifurcation windows consistent with recent experiments in yttrium iron ...


Shell Correction For The Stopping Power Of K Electrons, P.T. Leung, M. L. Rustgi, S. A. Long Apr 1986

Shell Correction For The Stopping Power Of K Electrons, P.T. Leung, M. L. Rustgi, S. A. Long

Physics Faculty Publications and Presentations

In view of the inapplicability of the asymptotic expressions for the stopping number available in the literature at high energies, an alternative approach is taken to compute the shell correction to the stopping number of K electrons. Anholt's formula (1979) for the K-shell ionization has been used to calculate the excitation function for longitudinal interaction and numerical integration over energy has been carried out to evaluate the shell correction. Comparison with other theoretical calculations is made. It is proposed that, with the inclusion of relativistic effects, an asymptotic expansion of the stopping number with a leading-term logarithmic in the ...


Relativistic Corrections To The Bethe Sum Rule, P.T. Leung, M. L. Rustgi, S. A. Long Apr 1986

Relativistic Corrections To The Bethe Sum Rule, P.T. Leung, M. L. Rustgi, S. A. Long

Physics Faculty Publications and Presentations

Relativistic corrections to order alpha² to the Bethe sum rule have been obtained for a one-electron system employing the Foldy-Wouthuysen transformation. The results have wide applications in high-Z systems at large momentum transfers.


Fabrication Of Bipolar Transistors By Maskless Ion Implantation, Robert H. Reuss, Damon Morgan, Ann Goldenetz, William M. Clark, David B. Rensch, Mark Utlaut Jan 1986

Fabrication Of Bipolar Transistors By Maskless Ion Implantation, Robert H. Reuss, Damon Morgan, Ann Goldenetz, William M. Clark, David B. Rensch, Mark Utlaut

Physics Faculty Publications and Presentations

The first focused ion beam (FIB) arsenic ion implants are reported. A shallow junction, vertical npn bipolar transistor fabricated by maskless implantation of B and As is described. For comparison, devices on the same wafer were also processed with conventional, broad‐beam B and/or As implants. Good transistor performance is obtained for each type of implanted transistor. Device characteristics for FIB and conventional implants are generally the same. However, initial results indicate that diode quality and junction leakage appear somewhat degraded (excess generation–recombination) for FIB arsenic implanted devices. Characteristics of FIB boron implanted devices obtained over an extended ...


The Focused Ion Beam As An Integrated Circuit Restructuring Tool, J. Melngailis, C. R. Musil, E. H. Stevens, Mark Utlaut, E. M. Kellogg, R. T. Post, M. W. Geis, R. W. Mountain Jan 1986

The Focused Ion Beam As An Integrated Circuit Restructuring Tool, J. Melngailis, C. R. Musil, E. H. Stevens, Mark Utlaut, E. M. Kellogg, R. T. Post, M. W. Geis, R. W. Mountain

Physics Faculty Publications and Presentations

One of the capabilities of focused ion beam systems is ion milling. The purpose of this work is to explore this capability as a tool for integrated circuit restructuring. Methods for cutting and joining conductors are needed. Two methods for joining conductors are demonstrated. The first consists of spinning nitrocellulose (a self‐developing resist) on the circuit, ion exposing an area, say, 7×7 μm, then milling a smaller via with sloping sidewalls through the first metal layer down to the second, e‐beam evaporating metal, and then dissolving the nitrocellulose to achieve liftoff. The resistance of these links between ...


Fock-Tani Transformation And A First-Order Theory Of Charge Transfer, P. C. Ojha, M. D. Girardeau, J. D. Gilbert, Jack C. Straton Jan 1986

Fock-Tani Transformation And A First-Order Theory Of Charge Transfer, P. C. Ojha, M. D. Girardeau, J. D. Gilbert, Jack C. Straton

Physics Faculty Publications and Presentations

A unitary (Fock-Tani) transformation of the second-quantized Hamiltonian breaks the interaction into its component parts, e.g., elastic scattering, inelastic scattering, rearrangement interaction, etc. The interaction for a particular process is ‘‘weaker’’ than the overall interaction; this is reflected in certain orthogonality corrections which appear in a perturbation expansion of the T-matrix element. As a result, the internuclear potential makes a negligible contribution of order me/mp to the first-order amplitude for charge transfer. We find very good agreement with experimental and the best available theoretical results for the total cross section for the reaction p+H ...


An Approximate Variational Method For Improved Thermodynamics Of Molecular Fluids, M. S. Shaw, J. D. Johnson, John D. Ramshaw Jan 1986

An Approximate Variational Method For Improved Thermodynamics Of Molecular Fluids, M. S. Shaw, J. D. Johnson, John D. Ramshaw

Physics Faculty Publications and Presentations

For a certain class of thermodynamic perturbation theories, a generalization of the Gibbs-Bogoliubov inequality holds through second order of perturbation theory and for a subset of terms the inequality is true to infinite order. Using this approximate variational principle, a perturbation theory is chosen for which the Helmholtz free energy of the reference system is minimized under the constraint that the first order term is identically zero. We apply these ideas to the determination of effective spherical potentials that accurately reproduce the thermodynamics of nonspherical molecular potentials. For a diatomic-Lennard-Jones (DLJ) potential with l ∕σ = 0.793, the resulting spherical ...