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Verbiest GJ, Janssen H, Xu D, Ge X, Goldsche M, Sonntag J, Khodkov T, Banszerus L, von den Driesch N, Buca D, Watanabe K, Taniguchi T, Stampfer C. Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic fields. Rev Sci Instrum 2019; 90:084706. [PMID: 31472650 DOI: 10.1063/1.5089207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 08/04/2019] [Indexed: 06/10/2023]
Abstract
We developed an impedance bridge that operates at cryogenic temperatures (down to 60 mK) and in perpendicular magnetic fields up to at least 12 T. This is achieved by mounting a GaAs HEMT amplifier perpendicular to a printed circuit board containing the device under test and thereby parallel to the magnetic field. The measured amplitude and phase of the output signal allows for the separation of the total impedance into an absolute capacitance and a resistance. Through a detailed noise characterization, we find that the best resolution is obtained when operating the HEMT amplifier at the highest gain. We obtained a resolution in the absolute capacitance of 6.4 aF/Hz at 77 K on a comb-drive actuator while maintaining a small excitation amplitude of 15 kBT/e. We show the magnetic field functionality of our impedance bridge by measuring the quantum Hall plateaus of a top-gated hBN/graphene/hBN heterostructure at 60 mK with a probe signal of 12.8 kBT/e.
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Affiliation(s)
- G J Verbiest
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - H Janssen
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - D Xu
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - X Ge
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - M Goldsche
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - J Sonntag
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - T Khodkov
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - L Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
| | - N von den Driesch
- Peter Grünberg Institute (PGI-8/9), Forschungszentrum Jülich, 52425 Jülich, Germany, EU
| | - D Buca
- Peter Grünberg Institute (PGI-8/9), Forschungszentrum Jülich, 52425 Jülich, Germany, EU
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU
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Goldsche M, Verbiest GJ, Khodkov T, Sonntag J, Driesch NVD, Buca D, Stampfer C. Fabrication of comb-drive actuators for straining nanostructured suspended graphene. Nanotechnology 2018; 29:375301. [PMID: 29924743 DOI: 10.1088/1361-6528/aacdec] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on the fabrication and characterization of an optimized comb-drive actuator design for strain-dependent transport measurements on suspended graphene. We fabricate devices from highly p-doped silicon using deep reactive ion etching with a chromium mask. Crucially, we implement a gold layer to reduce the device resistance from ≈51.6 kΩ to ≈236 Ω at room temperature in order to allow for strain-dependent transport measurements. The graphene is integrated by mechanically transferring it directly onto the actuator using a polymethylmethacrylate membrane. Importantly, the integrated graphene can be nanostructured afterwards to optimize device functionality. The minimum feature size of the structured suspended graphene is 30 nm, which allows for interesting device concepts such as mechanically-tunable nanoconstrictions. Finally, we characterize the fabricated devices by measuring the Raman spectrum as well as the a mechanical resonance frequency of an integrated graphene sheet for different strain values.
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Affiliation(s)
- M Goldsche
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, D-52074 Aachen, Germany. Peter Grünberg Institute (PGI-8/9), Forschungszentrum Jülich, D-52425 Jülich, Germany
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