Coaxial Electrical Circuits for Interference-Free Measurements

Awan, S.A.; Schurr,; Kibble,

doi:10.1049/pbel013e

Cited by 108 publications

(92 citation statements)

References 32 publications

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“…For ac measurements, an in-house developed fourterminal-pair coaxial ac resistance bridge whose design is described elsewhere [21] was used to compare the quantum Hall resistance of the graphene device with a 12.9 kΩ reference resistor which, in turn, had been measured at ac against well-characterized double-shielded GaAs QHR devices. Here, the graphene device was connected according to the triple-series connection scheme [22,23] (Fig.…”

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confidence: 99%

“…Note that for ac measurements bond wires of unused contacts (contacts 2 and 6 in our case) have to be removed, because otherwise the opencircuited lead capacitances would draw considerable ac currents through the device. These currents do not contribute to the current measurement, but cause an additional Hall voltage which would lead to a wrong Hall resistance [21]. Figure 3a shows precision ac measurements of the QHR at the ν = 2 plateau of the graphene device, presented as the relative deviation ∆r = (R xy -R K /2)/(R K /2) from R K /2 = h/2e 2 .…”

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Towards a graphene-based quantum impedance standard

Kalmbach

Schurr

Ahlers

et al. 2014

Applied Physics Letters

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Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10 7 . This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-fluxdependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8×10 -8 /kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance.Graphene is probably the most fascinating electronic material discovered in the last decades [1][2][3]. Among its various unique properties, an anomalous 'half-integer' quantum Hall effect (QHE) is most interesting for metrology, where the fact that the Hall resistance is quantized and depends only on fundamental constants is utilized for the representation and maintenance of the resistance unit, the ohm. Typically, twodimensional electron systems (2DES) realized in GaAs/AlGaAs heterostructures [4] are used for this purpose. The required relative measurement uncertainty of better than 1 part in 10 8 is, however, only obtained at strong magnetic fields around 10 tesla and at temperatures of 1.4 kelvin and below. In contrast, in graphene the cyclotron energy splitting between the Landau levels (which is the main factor determining the robustness of the quantized Hall resistance (QHR)) is so large that fingerprints of the QHE are even observed at room temperature [5]. Thus, with graphene a highly precise QHR standard working at low magnetic fields and temperatures above 4 kelvin is conceivable, which would be an enormous advantage for practical metrology. In fact, when measuring with direct current (dc), it has been demonstrated already that the precision of the QHE in high quality graphene devices matches that of GaAs devices [6][7][8][9]. However, in the forthcoming fundamental constant-based redefinition of the Système International d'Unités (SI) [10], also the impedance units (capacitance and inductance) will be traced to fundamental constants [11]. The most direct way to represent the impedance units is to use a quantum Hall resistance measured with alternating current (ac QHR). This has two advantages. Firstly, deriving the resistance and impedance units from the same quantum effect improves the consistency of the SI. And secondly, using the same QHE device at dc and at ac in one and the same cryomagnetic system would constitute a practical and economical advantage. Therefore, the question naturally arises whether graphene can replace GaAs also in the realm of impedance units, leading to an at least equally precise, but more userfriendl...

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Towards a graphene-based quantum impedance standard

Kalmbach

Schurr

Ahlers

et al. 2014

Applied Physics Letters

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“…The design must therefore feature complete isolation of the temperature control electronics from the measurement connections. The ideal approach is to use a fully screened definition of the standard compatible with use as an ac 'four terminal pair' standard (section 5.3 of [3]). This also has the advantage of controlling leakage resistances (which may become significant for standards of 10 kΩ and above).…”

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confidence: 99%

A transportable thermoregulated enclosure for standard resistors

Rolland

Goebel

Fletcher

2012

2012 Conference on Precision Electromagnetic Measurements

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“…Most suitable resistance values for a QHARS that would be used for realization of capacitance unit from QHE are in the range 50 kΩ -100 kΩ that can be realized by connecting e.g. 4 or 8 individual QHE devices in series [20]. The resistance of such an array is close to the impedances of most accurate capacitance standards at conventional frequency range 1 kHz -10 kHz.…”

Section: Introductionmentioning

confidence: 99%

Mini array of quantum Hall devices based on epitaxial graphene

Новиков

Лебедева

Hämäläinen

et al. 2016

Journal of Applied Physics

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Series connection of four quantum Hall effect (QHE) devices based on epitaxial graphene films was studied for realization of a quantum resistance standard with an up-scaled value. The tested devices showed quantum Hall plateaux R H,2 at filling factor ν = 2 starting from relatively low magnetic field (between 4 T and 5 T) when temperature was 1.5 K. Precision measurements of quantized Hall resistance of four QHE devices connected by triple series connections and external bonding wires were done at B = 7 T and T = 1.5 K using a commercial precision resistance bridge with 50 μA current through the QHE device.The results showed that the deviation of the quantized Hall resistance of the series connection of four graphene-based QHE devices from the expected value of 4×R H,2 = 2h/e 2 was smaller than the relative standard uncertainty of the measurement (< 1×10 -7 ) limited by the used resistance bridge.

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Coaxial Electrical Circuits for Interference-Free Measurements

Cited by 108 publications

References 32 publications

Towards a graphene-based quantum impedance standard

Towards a graphene-based quantum impedance standard

A transportable thermoregulated enclosure for standard resistors

Mini array of quantum Hall devices based on epitaxial graphene

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