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.
Summary
Graphene, the two-dimensional honeycomb carbon lattice isolated in 2004, has enabled significant advancement in a variety of subfields in physics due to its extraordinary electronic properties. Among those properties is the ability to sustain the quantum Hall effect with more relaxed experimental conditions that traditional semiconductors. Our role within NIST’s core mission is to develop cutting-edge quantum electrical devices that become definitive U.S. standards as well as to disseminate those end-user-friendly standards throughout the nation. Our wide-ranging efforts include: basic research to expand device functionality, applied innovations to solidify foundations of our calibration services, and executive plans to transfer knowledge, intellectual property, and technology to partners within the U.S. Government, academia, and private industry. We have utilized graphene to dramatically improve metrology based on the fundamental constants, becoming the first nation to use it for the dissemination of an electrical unit (ohm).
Description
Inset: Example of an array device design. (a) An illustration of the graphene quantized Hall array resistance device with NbTiN interconnections (dark grey) between individual QHR elements (light grey) and the positions of the bonding wires that were used for the measurement (blue). The red inset box marks the region shown in (b). (b) Confocal laser scanning microscope (CLSM) image of a graphene Hall bar device in the source/drain contact region using a multiple connection and superconducting split contacts (white). (c) CLSM image in the region of the graphene/NbTiN split contact shows the design used to realize negligible contact resistances. (d) The photo shows the contacted device (7.6 mm × 7.6 mm) mounted on a 32-pin chip carrier. (e) The scatter plot of Raman graphene 2D (G′) peak characteristics was evaluated from 50 μm × 50 μm area maps. (f) The graph shows the vanishing resistance across a superconducting element of the device for different temperatures and magnetic flux densities.
The quantum Hall effect (QHE), and devices that exhibit it, will continue to serve as the foundation of the ohm while also expanding its territory into other SI derived units. The world adopted the quantum SI in 2019, and it remains essential that the global metrology community pushes forth and continues to innovate and produce new technologies for disseminating the ohm and other electrical units.
For electrical standards, considerations must be made regarding two important factors in metrology: simplicity of operation and total accessible parameter space. In the case of GaAs, the required infrastructure to achieve well-quantized resistances is demanding compared to using epitaxially grown graphene on SiC. It has been established that graphene-based QHE devices can exhibit a distinct advantage over GaAs-based devices when attempting to use low magnetic fields, higher temperatures, and larger currents. Improvement of devices to expand accessibility is expected to correlate with the reduction in cost and complexity of quantized Hall resistance (QHR) standards for metrology as well as any associated laboratory measurement apparatus.
For a few years, epitaxial graphene has been used as part of the electrical resistance dissemination service in the United States. The preceding years were primarily dedicated to optimizing the technology and fabrication processes so that graphene-based QHR devices could be deployed into U.S. and global industries. We at NIST are presently collaborating with partners in academia, industry, and other U.S. government agencies to improve such devices even further and to build a detailed understanding of their functional principles. More specifically, we hope to expand SI traceability beyond the usual single value obtained with the QHE by developing graphene array devices. These devices would reduce dependency on artifact standards that are prone to time-dependent changes.
Enhanced and straightforward traceability to the QHR is one of the goals of the project, especially to assist customers who use room-temperature measurement systems. Another major goal of the project is to expand accessibility to more orders of magnitude of the ohm using graphene-based array devices, which provide multiple quantized resistance values. Looking forward, this project will explore the QHE in systems that may only require small permanent magnets, with topological insulators as the prime example. Furthermore, it looks to expand the utility of graphene-based devices in efforts to create a quantized current source.
Interested in Reading More About Graphene?
Major Accomplishments
- Epitaxial growth for homogeneous graphene achieved at the centimeter scale
- Successful process developed for controlling the carrier density of graphene on the millimeter scale without electrostatic gating
- Device technologies have been filed as patents and are undergoing technology transfer to industry partners
- Gold Medal received by the U.S. Department of Commerce in 2018 (along with the Metrology of the Ohm project) for this pioneering work
REFERENCES of recent Major Accomplishments
“Graphene quantum Hall effect parallel resistance arrays,” Alireza R. Panna et al., Phys. Rev. B, 103:075408, Feb 2021
https://doi.org/10.1103/PhysRevB.103.075408
“Magnetotransport in hybrid InSe/monolayer graphene on SiC,” Chih-Yuan Wang et al., Nanotechnology, 32(15):155704, jan 2021
https://doi.org/10.1088/1361-6528/abd726
“Thermoelectric transport in coupled double layers with interlayer excitons and exciton condensation,” Jiuning Hu et al., PHYSICAL REVIEW B 102, 235304, dec 2020
https://doi.org/10.1103/PhysRevB.102.235304
“Development of gateless quantum Hall checkerboard p-n junction devices,” Dinesh K Patel et al., Journal of Physics D: Applied Physics, 53(34):345302, jun 2020
https://doi.org/10.1088/1361-6463/ab8d6f
“Nanostructured graphene for nanoscale electron paramagnetic resonance spectroscopy,” Luke St Marie et al., Journal of Physics: Materials, 3(1):014013, jan 2020
https://doi.org/10.1088/2515-7639/ab6af8
“Implementation of a graphene quantum Hall Kelvin bridge-on-a-chip for resistance calibrations,” Martina Marzano et al., Metrologia, 57(1):015007, jan 2020
https://doi.org/10.1088/1681-7575/ab581e
“A four-terminal-pair Josephson impedance bridge combined with a graphene quantized Hall resistance,” Stephan Bauer et al., Measurement Science and Technology, 2020
https://doi.org/10.1088/1361-6501/abcff3
“Elucidating charge transport mechanisms in cellulose-stabilized graphene inks,” Ana C. M. de Moraes et al., J. Mater. Chem.C, 8:15086-15091, 2020
https://doi.org/10.1039/D0TC03309J
“Accessing ratios of quantized resistances in graphene p{n junction devices using multiple terminals,” Dinesh Patel et al., AIP Advances, 10(2):025112, 2020
https://doi.org/10.1063/1.5138901
“Analytical determination of atypical quantized resistances in graphene p-n junctions,” Albert F. Rigosi et al., Physica B: Condensed Matter, 582:411971, 2020
https://doi.org/10.1016/j.physb.2019.411971
“A self assembled graphene ribbon device on SiC,” Bi-Yi Wu et al., ACS Applied Electronic Materials, 2(1):204-212, 2020
https://doi.org/10.1021/acsaelm.9b00696
“Next-generation crossover-free quantum Hall arrays with superconducting interconnections,” Mattias Kruskopf et al., Metrologia, 56(6):065002, oct 2019
https://doi.org/10.1088/1681-7575/ab3ba3
”The quantum Hall effect in the era of the new SI,” Albert F Rigosi and Randolph E Elmquist, Semiconductor Science and Technology, 34(9):093004, aug 2019
https://doi.org/10.1088/1361-6641/ab37d3
“Graphene devices for tabletop and high-current quantized Hall resistance standards,” A. F. Rigosi et al., IEEE Transactions on Instrumentation and Measurement, 68(6):1870-1878, 2019
https://doi.org/10.1109/TIM.2018.2882958