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Displaying 126 - 150 of 275

Insulator-quantum Hall transition in monolayer epitaxial graphene

July 22, 2016
Author(s)
Lung-I Huang, Yanfei Yang, Randolph Elmquist, Shun-Tsung Lo, Fan-Hung H. Liu, Chi-Te Laing
We report on magneto-transport measurements on low-density, large-area monolayer epitaxial graphene devices grown on SiC. We observe temperature (T)-independent crossing points in the longitudinal resistivity (rho)sub(xx), which are signatures of the

Quantum Hall Resistance Traceability for the NIST-4 Watt Balance

July 10, 2016
Author(s)
Dean G. Jarrett, Randolph Elmquist, Marlin E. Kraft, George R. Jones Jr., Shamith Payagala, Frank Seifert, Stephan Schlamminger, Darine El Haddad
Scaling from the quantum Hall resistance to 100 Ω standard resistors used by the NIST-4 Watt Balance involves multiple resistance standards and bridges to provide the lowest possible uncertainty. Described here is the infrastructure and procedures

Surface conductance of graphene from non-contact resonant cavity

March 15, 2016
Author(s)
Jan Obrzut, Caglar Dogu Emiroglu, Oleg A. Kirillov, Yanfei Yang, Randolph E. Elmquist
A method is established to reliably determine surface conductance of single-layer or multi-layer atomically thin nano-carbon graphene structures. These can be synthesized by chemical vapor deposition (CVD), epitaxial growth on silicon carbide (SiC)

Low-Ohmic Resistance Comparison: Measurement Capabilities and Resistor Traveling Behavior

March 1, 2016
Author(s)
Marlin E. Kraft, Randolph E. Elmquist, Gert Rietveld, Jan van der Beek, Alessandro Mortara, Beat Jeckelmann
The low-ohmic resistance measurement capabilities of the Van Swinden Laboratorium, National Institute of Standards and Technology, and the Federal Office of Metrology (METAS) were compared using a set of resistors with values 100 mΩ, 10 mΩ, 1 mΩ, and 100

Reference Module in Materials Science and Materials Engineering MATS 01908

February 1, 2016
Author(s)
Randolph E. Elmquist, Anthony Hartland
The cryogenic current comparator is used to maintain national representations of the ohm based on the quantized Hall resistance standard. The measurement technique utilizes the Meissner effect to establish accurate resistance ratios with specialized

Quantized Hall resistance in large-scale monolayer graphene

November 28, 2015
Author(s)
Yanfei Yang, Chiashain Chuang, Chieh W. Liu, Randolph Elmquist
Abstract: Graphene is an atomic-thickness carbon lattice that can be exfoliated from solid graphite or grown using high temperature processing methods on a variety of substrates. Many practical applications of large-area graphene, however, are limited by

Transportation Effect and Basic Characteristics of Ni-Cr Based Metal-Foil Standard Resistors Examined in a Trilateral Comparison Pilot Study between KRISS, NIST and NMIJ

June 1, 2015
Author(s)
Marlin E. Kraft, Randolph E. Elmquist, Nobu-hisa Kaneko, Wan-Seop Kim, Dong Hun Chae, Takehiko Oe
The transportation effect and other important characteristics of 100-Ω standard resistors of a new construction have been studied. For transportation effect, four resistors have been transported by air between three national metrology institutes: the Korea

Development of Low Carrier Density Graphene Devices

August 1, 2014
Author(s)
Yanfei Yang, Lung-I Huang, David B. Newell, Yasuhiro Fukuyama, Mariano A. Real, Randolph Elmquist
Epitaxial graphene on SiC(0001) is used to fabricate Hall bar structures for metrological applications with a fabrication process that has been developed to eliminate organic chemical contamination of the graphene. Before any lithographic patterning a

Transportation Effect of the Ni-Cr Based Metal-Foil Standard Resistors in the Trilateral Comparison Pilot Study between KRISS, NIST and NMIJ

August 1, 2014
Author(s)
Randolph E. Elmquist, Nobu-hisa Kaneko, Takehiko Oe, Wan-Seop Kim, Dong Hun Chae, Marlin E. Kraft
This paper describes a study on the transportation effect using four 100 Ω standard resistors of a new construction. All resistors have been transported by air: two of the resistors in hand-carried luggage and the other two by normal air freight. The

Low carrier density epitaxial graphene devices on SiC

June 1, 2014
Author(s)
Yanfei Yang, Lung-I Huang, Yasuhiro Fukuyama, Fan-Hung Liu, Mariano Real, Paola Barbara, Chi-Te Liang, David B. Newell, Randolph Elmquist
Monolayer epitaxial graphene grown on a hexagonal silicon carbide (SiC) substrate is typically found to be heavily n-doped (10e13 cm-2) and in most devices made with the as-grown epitaxial graphene the quantized Hall resistance plateau with Landau level

Localization and electron-electron interactions in few-layer epitaxial graphene

May 28, 2014
Author(s)
Randolph E. Elmquist, Fan-Hung Liu, Lung-I Huang, Yasuhiro Fukuyama, Chi-Te Liang, Yanfei Yang
We study the quantum corrections caused by electron-electron (e-e) interactions and localization to the conductivity in few-layer epitaxial graphene, in which the carriers responsible for transport are massive. Our results demonstrate that the diffusive

Precision high-value resistance scaling with a two-terminal cryogenic current comparator

March 1, 2014
Author(s)
Randolph E. Elmquist, George R. Jones, Felipe L. Hernandez-Marquez, Marcos Bierzychudek
We describe a cryogenic two-terminal high-resistance bridge and its application in precision resistance scaling from the quantized Hall resistance (QHR) at RH = RK/2 = 12 906.4035 _ to decade resistance standards with values between 1 M_ and 1 G_. The