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Search Publications by

Randolph Elmquist (Fed)

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Displaying 1 - 25 of 120

Graphene Quantum Hall Effect Parallel Resistance Arrays

February 2, 2021
Alireza Panna, I Fan Hu, Mattias Kruskopf, Dinesh K. Patel, Dean G. Jarrett, Chieh-I Liu, Shamith Payagala, Dipanjan Saha, David B. Newell, Chi-Te Liang, Randolph Elmquist, Albert Rigosi
As first recognized in 2010, epitaxial graphene on SiC(0001) provides a platform for quantized Hall resistance (QHR) metrology unmatched by other 2D structures and materials. Here we report graphene parallel QHR arrays, with metrologically precise

AC and DC Quantized Hall Array Resistance Standards

August 28, 2020
Randolph E. Elmquist, Mattias Kruskopf, Dinesh K. Patel, I Fan Hu, Chieh-I Liu, Albert F. Rigosi, Alireza R. Panna, Shamith U. Payagala, Dean G. Jarrett
Quantized Hall array resistance standards (QHARS) span values from 100 (ohm) to 1 M(ohm) and demonstrate precision approaching that of single devices. This paper focuses on QHARS having values near 1 k(ohm) for increased sensitivity using room-temperature

Graphene quantum Hall effect devices for AC and DC resistance metrology

August 28, 2020
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
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
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
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 10, 2019
Jan Obrzut, Keith White, Yanfei Yang, Randolph E. 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