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Physics

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Displaying 2376 - 2400 of 2574

X-ray diffraction, photoluminescence and composition standards of compound semiconductors

January 1, 2003
Author(s)
Alexana Roshko, Kristine A. Bertness, J T. Armstrong, Ryna B. Marinenko, Marc L. Salit, Lawrence H. Robins, Albert J. Paul, R J. Matyi
Work is underway to develop composition standards and standardized assessment procedures for compound semiconductors. An AlGaAs composition standard with less than 2% uncertainty is being developed. The improved accuracy of this standard is being achieved

Composition standards for III-V semiconductor epitaxial films

November 11, 2002
Author(s)
Kristine A. Bertness, Lawrence H. Robins, J T. Armstrong, Ryna B. Marinenko, Albert J. Paul, Marc L. Salit
A program is underway at NIST to establish standard reference materials (SRMs) for the calibration of instruments used to measure the chemical composition of epitaxially grown III-V semiconductor thin films. These SRMs are designed for the calibration of

Trace water detection in semiconductor-grade phosphine gas

November 11, 2002
Author(s)
Kristine A. Bertness, Susan Y. Lehman, Joseph T. Hodges, H. H. Funke, Mark W. Raynor
We are applying cavity ring-down spectroscopy (CRDS) to measure water concentrations in nitrogen and, for the first time to our knowledge, in phosphine. Semiconductor-grade phosphine cylinders from different suppliers contained water in the several ppm

Four-state measurement method for polarization dependent wavelength shift

September 1, 2002
Author(s)
William C. Swann, Shellee D. Dyer, Rex M. Craig
We present a novel four-state method for measuring the polarization dependent wavelength shift (PDW) of a fiber Bragg grating. We show that measurement of the grating's wavelength for only four different polarization states is sufficient to completely

Threshold Resonance Spectroscopy: A Key to Cold Collision Physics

September 1, 2002
Author(s)
Paul S. Julienne
Threshold scattering resonances play a crucial role in cold collision physics and cold molecule formation from cold atoms. We describe several examples involving magnetic Feshbach spectroscopy of Cs atoms, photoassociation of Na atoms in a Bose-Einstein

Formation of InAs/GaAs quantum dots by dewetting during cooling

July 1, 2002
Author(s)
Richard P. Mirin, Alexana Roshko, M. van der Puijl, Andrew G. Norman
We describe a method to form InAs quantum dots on GaAs by cooling an InAs film that is deposited at high substrate temperatures. The reflection high-energy electron diffraction pattern taken after deposition of 1.9 monolayers of InAs on (100) GaAs at 540

Wavelength references for 1300-nm wavelength division multiplexing

May 1, 2002
Author(s)
Tasshi Dennis, E. A. Curtis, C. W. Oates, Leo W. Hollberg, Sarah L. Gilbert
We have conducted a study of potential wavelength calibration references for use as both moderate-accuracy transfer standards and high-accuracy National Institute of Standards and Technology (NIST) internal references in the 1280-1320 nm wavelength

Wavenumber Standards for Mid-Infrared Spectrometry

February 1, 2002
Author(s)
Leonard M. Hanssen, C. J. Zhu
Accuracy of the wavenumber scale of spectroscopic instrumentation is fundamentally important for most applications. Most modern Fourier transform spectrophotometers (FTS) incorporate HeNe lasers that are used to set the wavenumber scale for the instrument

Mass Absorption Coefficient of Tungsten, 1600 eV to 2100 eV

January 24, 2002
Author(s)
Zachary H. Levine, S Grantham, I McNulty
The transmission of soft x-rays with photon energies from 1606 eV to 2106 eV was measured for tungsten using thin film samples and a synchrotron source. This region includes the M IV and M V edges. The two tungsten films had thicknesses of 107.7 10 nm and

Calibration of a Heat Flux Sensor Up to 200 kW/m 2 in a Spherical Blackbody Cavity

January 1, 2002
Author(s)
A V. Murthy, Benjamin K. Tsai, Robert D. Saunders
This paper presents the results of a comparative study of narrow view-angle and wide view-angle calibrations of a water-cooled Schmidt-Boelter heat-flux sensor. The narrow view-angle calibration, up to a heat flux level of 50 kW/m2, was conducted using the

Comparison of AlGaAs oxidation in MBE and MOCVD grown samples

January 1, 2002
Author(s)
Y Chen, Alexana Roshko, Kristine A. Bertness, Dennis W. Readey, Marc A. Mansfield, M. Tan, A. Tandon
Simultaneous wet thermal oxidation of MBE and MOCVD grown Al xGa 1-xAs layers showed that the epitaxial growth method does not influence the oxidation rate. Nearly identical oxidation depths were measured for samples grown by both techniques. It was found
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