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84 results on '"Perz, J. M."'

1. Modeling of disordered materials: radial distribution function vs. vibrational spectra as a protocol for validation

Author

Gaspari, F., Kupchak, I. M., Shkrebtii, A. I., and Perz, J. M.

Subjects
Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Materials Science
Abstract

As molecular dynamics is increasingly used to characterize non-crystalline materials, it is crucial to verify that the numerical model is accurate enough, consistent with experimental data and can be used to extract various characteristics of disordered systems. In most cases the only derived property used to test the "realism" of the models has been the radial distribution function. We report extensive ab-initio simulation of hydrogenated amorphous silicon that demonstrates that although agreement with the RDF is a necessary requirement, this protocol is insufficient for the validation of a model. We prove that the derivation of vibrational spectra is a more efficient and valid protocol to ensure the reproducibility of macroscopic experimental features., Comment: 9 pages, 7 figures

Published
2008

2. Elastic Tensor of Sr$_2$RuO$_4$

Author

Paglione, Johnpierre, Lupien, C., MacFarlane, W. A., Perz, J. M., Taillefer, Louis, Mao, Z. Q., and Maeno, Y.

Subjects
Condensed Matter - Superconductivity
Abstract

The six independent elastic constants of Sr$_2$RuO$_4$ were determined using resonant ultrasound spectroscopy on a high-quality single-crystal specimen. The constants are in excellent agreement with those obtained from pulse-echo experiments performed on a sample cut from the same ingot. A calculation of the Debye temperature using the measured constants agrees well with values obtained from both specific heat and M\"{o}ssbauer measurements., Comment: 4 pages, 2 figures, 2 tables, submitted to PRB

Published
2002
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6. Temperature dependent vibrational spectra and bond dynamics in hydrogenated amorphous silicon.

Author

Kupchak, I. M., Gaspari, F., Shkrebtii, A. I., and Perz, J. M.

Subjects
SILICON, MOLECULAR dynamics, VIBRATIONAL spectra, SPECTRUM analysis, SIGNAL processing, STRUCTURAL stability
Abstract

We present the results of extensive modeling of hydrogenated amorphous silicon (a-Si:H) by combined ab initio molecular dynamics, an improved signal processing technique, and computer visualization, focusing on vibrational properties of a-Si:H. By comparing the theoretical and experimental vibrational spectra we correlate the hydrogen and silicon dynamics with the structural stability, bonding geometry, and diffusion in the a-Si:H material. Microscopic characteristics that cannot be obtained by other techniques, namely, hydrogen migration, bond switching, and silicon dangling bond passivation, are extracted from the atomic dynamics. We also demonstrate that this method offers the possibility of accessing other important macroscopic characteristics of a-Si:H and its stability in general. The approach we have developed can be used as well to model all aspects of a-Si:H dynamics, including the detrimental Staebler–Wronski effect. [ABSTRACT FROM AUTHOR]

Published
2008
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7. Spatially resolved space-charge density in the hydrogenated amorphous silicon Schottky barrier from surface photovoltage measurements.

Author

Ukah, C. I., Perz, J. M., and Zukotynski, S.

Subjects
*ELECTRIC capacity, *AMORPHOUS substances, *SCHOTTKY barrier diodes, *SEMICONDUCTOR junctions
Abstract

Describes a procedure for the derivation of the differential capacitance of the hydrogenated amorphous silicon Schottky barrier (SB) from surface photovoltage measurements. Result of the illumination of amorphous silicon SB with light of appropriate wavelength; Explanation for the variation in junction capacitance in amorphous silicon; Details of experimental techniques used.

Published
1990
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8. Surface photovoltage spectroscopy in hydrogenated amorphous silicon.

Author

Ukah, C. I., Perz, J. M., and Zukotynski, S.

Subjects
*SCHOTTKY barrier diodes, *SILICON, *AMORPHOUS semiconductors, *SPECTRUM analysis
Abstract

Presents information on a study which investigated the properties of the amorphous silicon schottky barrier by surface photovoltage spectroscopy. Methodology of the study; Results and discussion.

Published
1989
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16. Elastic tensor ofSr2RuO4

Author

Paglione, Johnpierre, primary, Lupien, C., additional, MacFarlane, W. A., additional, Perz, J. M., additional, Taillefer, Louis, additional, Mao, Z. Q., additional, and Maeno, Y., additional

Published
2002
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17. De Haas-van Alphen effect in the band antiferromagnet FeGe2: Development of spin splitting.

Author

Grechnev, G. E., Lyogenkaya, A. A., Pluzhnikov, V. B., Svechkarev, I. V., Fedorchenko, A. V., and Perz, J. M.

Subjects
DE Haas-van Alphen effect, ANTIFERROMAGNETIC materials, FERMI surfaces, OSCILLATIONS, ELECTRONIC band structure, CONDUCTION electrons, SPIN-polarized currents
Abstract

The de Haas-van Alphen (dHvA) effect in the antiferromagnetic compound FeGe2 is studied experimentally. A sharp suppression of the amplitude of the first harmonic of the dHvA oscillations is observed for a number of orbits on the Fermi surface of FeGe2. The change in the conditions for suppression of the amplitude ("spin zeroes") when FeGe2 is doped with cobalt is determined. A method for analyzing the experimental data is proposed in which the g-factors of the conduction electrons are computed on the basis of calculations of the spin-polarized electron structure of the band antiferromagnet taking spin-orbital interactions into account. The exchange enhancement factor for spin paramagnetism in FeGe2 is also calculated. [ABSTRACT FROM AUTHOR]

Published
2014
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26. Superconductivity of barium-doped Bi2Sr2CaCu2Oy

Author

Yang, Beifang, Martin, Airton, Lee, M. J. G., and Perz, J. M.

Abstract

Sintered ceramic samples of Bi2Sr2-xBaxCaCu2Oy with nominal barium fraction 0=x=0.3 have been prepared by the solid-state reaction method. WDS studies verified that barium enters the superconducting phase. For slowly cooled samples, the midpointTc of the superconducting transition is significantly increased by barium doping, whereas for quenched samplesTc is little affected. The increase ofTc with increasing barium fraction is consistent with a decrease in the hole concentration in the superconducting layers.

Published
1996
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