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Displaying 51 - 75 of 82

Accuracy of AlGaAs Growth Rates and Composition Determination Using RHEED Oscillations

January 1, 2003
Author(s)
Todd E. Harvey, Kristine A. Bertness, Robert K. Hickernell, C. M. Wang, Jolene Splett
We investigate the sources of uncertainty in the measurement of the reflection high-energy electron diffraction (RHEED) intensity oscillations during growth of AlAs, GaAs, and AlGaAs on GaAs substrates, and the resulting effects on predicted growth rates

Accuracy of AlGaAs Rates and Composition Determination Using RHEED Oscillations

September 1, 2002
Author(s)
Todd E. Harvey, Kristine A. Bertness, Chih-Ming Wang, Jolene Splett
Reflection high-energy electron diffraction (RHEED) oscillations are widely used in molecular beam epitaxy (MBE) as a technique to calibrate material growth rates. The growth rates are used to predict the composition of the following growth run. For many

Controlled Barrier Modification in Nb/NbOx/Ag Metal Insulator Metal Tunnel Diodes

June 15, 2002
Author(s)
Erich N. Grossman, Todd E. Harvey, Carl D. Reintsema
The nonlinear electrical transport properties of metal-insulator-metal (MIM) tunnel diodes based on a barrier of naturally grown niobium oxide have been measured at room temperature and analyzed. In most cases excellent agreement is found between the

Properties of Cavity-Backed Slot-Ring Antennas at 95 GHZ

August 1, 2001
Author(s)
Shalva Nolen, Todd E. Harvey, Carl D. Reintsema, Erich N. Grossman
Slot-ring antennas with planar backshorts, designed for operation at 95 GHz, have been fabricated and their properties measured. Using optical lithography, we fabricated the slot-ring antennas, along with integrated niobium thin-film biolometers, on

1 Volt Josephson Fast Reversed DC Source

May 1, 2000
Author(s)
Charles J. Burroughs, Samuel Benz, Todd E. Harvey, H. Sasaki
We have made several improvements to the NIST Josephson FRDC (fast reversed dc) source so that it now operates at 1 Volt. We have made a precision comparison to a conventional semiconductor FRDC source by measuring the thermoelectric transfer difference of

1 Volt DC Programmable Josephson Voltage Standard System

June 1, 1999
Author(s)
Charles J. Burroughs, Samuel Benz, Todd E. Harvey, Clark A. Hamilton
NIST has developed a programmable Josephson voltage standard (JVS) that produces intrinsically stable voltages that are programmable from -1.1 V to +1.1 V.

Operating Conditions for a Pulse-Quantized AC and DC Bipolar Voltage Source

June 1, 1999
Author(s)
Samuel Benz, Charles J. Burroughs, Todd E. Harvey, Clark A. Hamilton
We have developed an accurate ac and dc bipolar voltage source based on the quantized pulses of Josephson junctions. A factor-of-6 increase in output voltage over previous unipolar waveforms is achieved by generating bipolar waveforms where arrays of

Superconducting Thin-Film Transformers at Microwave Frequencies

June 1, 1999
Author(s)
A. H. Miklich, J. X. Przybysz, T. J. Smith, Samuel Benz, Todd E. Harvey
We describe the use of thin-film superconducting transformers at frequencies up to 20 GHz. Transformers with turns ratios of 2,3, and 7 were fabricated out of Nb and tested in a liquid-He Dewar. The measured S-parameters showed considerably less bandwidth

Programmable 1 V DC Voltage Standard

April 1, 1999
Author(s)
Charles J. Burroughs, Samuel Benz, Clark A. Hamilton, Todd E. Harvey
We have developed a Josephson voltage standard that produces intrinsically stable voltages that are programmable of 32 768 SNS (superconductor-normal-superconductor) Josephson junctions. The output can source or sink up to 2 mA and thus has high noise

Pulse-Driven Josephson Digital/Analog Converter

June 1, 1998
Author(s)
Samuel Benz, Clark A. Hamilton, Charles J. Burroughs, Todd E. Harvey, Laurie Christian, J. X. Przybysz
We have designed and demonstrated a pulse-driven Josephson digital/analog converter. When used as a programmable voltage standard, this device can synthesize metrologically accurate ac waveforms as well as stable dc voltages. We show through simulations