U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by: Randolph Elmquist (Fed)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 26 - 50 of 137

Graphene quantum Hall effect devices for AC and DC resistance metrology

August 28, 2020
Author(s)
Mattias Kruskopf, Dinesh K. Patel, Chieh-I Liu, Albert Rigosi, Randolph Elmquist, Yicheng Wang, Stefan Bauer, Yefei Yin, Klaus Pierz, Eckard Pesel, Martin Goetz, Jurgen Schurr
The frequency dependence of the quantized Hall resistance at alternating current results from capacitive losses inside the sample as well as between the sample and external parts. In this joint effort we report on ac quantum Hall measurements of a graphene

Elucidating Charge Transport Mechanisms in Graphene Inks

August 7, 2020
Author(s)
Ana C. de Moraes1, Jan Obrzut, Vinod K. Sangwan, Julia R. Downing, Lindsay E. Chaney, Dinesh K. Patel, Randolph Elmquist, Mark C. Hersam
Solution-processed graphene inks using ethyl cellulose polymer as a binder/stabilizer were blade-coated into large area films. Systematic charge transport characterization showed graphene patterns with high mobility ( 160 cm2 V-1 s-1), low energy gap

A self-assembled graphene ribbon grown on SiC

January 2, 2020
Author(s)
Bi Y. Wu, Yanfei Yang, Albert Rigosi, Jiuning Hu, Hsin Y. Lee, Guangjun Cheng, Vishal Panchal, Mattias Kruskopf, Hanbyul Jin, Kenji Watanabe, Takashi Taniguchi, David B. Newell, Randolph Elmquist, Chi-Te Liang

Designing new structures in epitaxial graphene on SiC: transport and quantum effects

May 13, 2019
Author(s)
Randolph E. Elmquist, Hanbyul Jin, Mattias Kruskopf, Martina Marzano, Dinesh K. Patel, Alireza R. Panna, Albert F. Rigosi
When epitaxial graphene (EG) grows on hexagonal SiC(0001), chemical doping is produced by bonds at the epitaxial interface, or buffer layer. Robust quantum Hall effect (QHE) plateaus are observed at RK/2 = h/2e2, where RK is a constant of electrical

Characterization of graphene conductance using a microwave cavity

January 9, 2019
Author(s)
Jan Obrzut, Keith White, Yanfei Yang, Randolph Elmquist
Surface conductance of graphene films is investigated in a non-contact microwave cavity operating at 7.4543 GHz. This cavity technique characterizes specimens with high accuracy, without disruption of morphological integrity and without the processing

Utilizing confocal laser scanning microscopy for rapid optical characterization of graphene

November 20, 2018
Author(s)
Vishal Panchal, Yanfei Yang, Guangjun Cheng, Jiuning Hu, Mattias Kruskopf, Chieh-I Liu, Albert Rigosi, Christos Melios, Angela R. Hight Walker, David B. Newell, Olga Kazakova, Randolph Elmquist
Confocal laser scanning microscopy (CLSM) is a non-destructive, highly-efficient optical characterization method for large-area analysis of graphene on different substrates, which can be applied in ambient air, does not require additional sample

Part-per-million quantization and current-induced breakdown of the quantum anomalous Hall effect

August 27, 2018
Author(s)
Eli J. Fox, Ilan T. Rosen, Yanfei Yang, George R. Jones Jr., Randolph Elmquist, Xufeng Kou, Lei Pan, Kang L. Wang, D. Goldhaber-Gordon
In the quantum anomalous Hall effect, quantized Hall resistance and vanishing longitudinal resistivity are predicted to result from the presence of dissipationless, chiral edge states and an insulating two-dimensional bulk, without requiring an external

Epitaxial graphene for quantum resistance metrology

July 20, 2018
Author(s)
Mattias Kruskopf, Randolph Elmquist
A new generation of graphene-based quantum Hall resistance standards promises high precision for the unit ohm under relaxed measurement conditions, enabling the use of compact measurement systems. To meet the requirements of metrological applications

Quantum transport in graphene p-n junctions with Moire superlattice modulation

July 12, 2018
Author(s)
Jiuning Hu, Albert Rigosi, Ji Ung Lee, Hsin Y. Lee, Yanfei Yang, Chieh-I Liu, Randolph Elmquist, David B. Newell
This work presents simulations of quantum transport in graphene p-n junctions (pnJs) in which Moire superlattice potentials are incorporated to demonstrate the interplay of the effect of pnJs and Moire superlattice potentials. It is shown that the

Epitaxial Graphene for High-Current QHE Resistance Standards

July 9, 2018
Author(s)
Mattias Kruskopf, Jiuning Hu, Bi Y. Wu, Yanfei Yang, Hsin Y. Lee, Albert F. Rigosi, David B. Newell, Randolph E. Elmquist
We report the growth of large-area monolayer graphene on the centimeter scale using an optimized growth process allowing for reproducibility and morphology improvements. Magneto-transport measurements on graphene quantum Hall effect devices demonstrate the

Epitaxial Graphene p-n Junctions

July 9, 2018
Author(s)
Jiuning Hu, Mattias Kruskopf, Yanfei Yang, Bi Y. Wu, Jifa Tian, Alireza R. Panna, Albert F. Rigosi, Hsin Y. Lee, George R. Jones Jr., Marlin E. Kraft, Dean G. Jarrett, Kenji Watanabe, Takashi Taniguchi, Randolph E. Elmquist, David B. Newell
We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexgonal boron nitride (hBN) is used as the gate dielectric. The four terminal longitudinal resistance across a single junction is well quantized at R_