Magnetocapacitance and loss factor of GaAs quantum Hall effect devices

Schurr, J.; Ahlers, F. J.; Pierz, K.

doi:10.1088/0026-1394/51/3/235

Cited by 8 publications

(4 citation statements)

References 30 publications

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“…More detailed studies of the different contributions and of the dissipation factor of the SiC substrate and the ZEP520 resist in comparison to a GaAs substrate will be carried out in the future. Measurements of the magnetocapacitance of the 2DES and the associated dissipation factor [28] will enable further insight into the ac properties of graphene devices. Careful engineering of device and contact dimensions may allow achieving a frequency-independent quantum Hall resistance without need for a complex shielding method and the respective adjustments, leading to a graphene-based impedance standard which is as accurate as double-shielded GaAs devices, but more user-friendly and simpler to operate.…”

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confidence: 99%

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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confidence: 99%

Towards a graphene-based quantum impedance standard

Kalmbach

Schurr

Ahlers

et al. 2014

Applied Physics Letters

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“…The predictions of the RK model were also verified experimentally [20,21]. Other circuit models were developed in later years [21][22][23][24][25][26][27][28] and a general method of analysis based on the indefinite admittance matrix has been recently proposed [29].…”

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confidence: 86%

“…Sosso-Capra [25,26] 5. Schurr et al [27,28] 6. This work (appendix A) SPICE element to compose larger circuits in a hierarchical way.…”

Section: Spice Modellingmentioning

confidence: 99%

Circuit models and SPICE macro-models for quantum Hall effect devices

Ortolano

Callegaro

2015

Meas. Sci. Technol.

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Abstract. Quantum Hall effect (QHE) devices are a pillar of modern quantum electrical metrology. Electrical networks including one or more QHE elements can be used as quantum resistance and impedance standards. The analysis of these networks allows metrologists to evaluate the effect of the inevitable parasitic parameters on their performance as standards. This paper presents a systematic analysis of the various circuit models for QHE elements proposed in the literature, and the development of a new model. This last model is particularly suited to be employed with the analogue electronic circuit simulator SPICE. The SPICE macro-model and examples of SPICE simulations, validated by comparison with the corresponding analytical solution and/or experimental data, are provided.Circuit models and SPICE macro-models for quantum Hall effect devices 2

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“…In particular, parasitic capacitive effects have to be explored in detail because so far even their magnitude is unknown. Measurements of the magneto capacitance and the associated loss factor [8] as well as noise power measurements [9] of graphene devices may reveal new insights into the quantum Hall effect as well as interesting findings relevant to the application of the quantum Hall effect.…”

Section: Introductionmentioning

confidence: 99%

First ac measurements of the quantum Hall effect in epitaxial graphene

Kalmbach

Schurr

Ahlers

et al. 2014

29th Conference on Precision Electromagnetic Measurements (CPEM 2014)

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We present first ac measurements of the quantized Hall resistance in graphene. Remarkably, the first results are very similar to that of conventional, unshielded GaAs devices. The future exploration of the detailed loss mechanisms in graphene by established ac analysis techniques thus gives a good chance to understand and to eliminate the ac losses, enabling a future graphene-based impedance standard.Index Terms -Graphene, quantum Hall effect, impedance, spectral noise density.

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Magnetocapacitance and loss factor of GaAs quantum Hall effect devices

Cited by 8 publications

References 30 publications

Towards a graphene-based quantum impedance standard

Towards a graphene-based quantum impedance standard

Circuit models and SPICE macro-models for quantum Hall effect devices

First ac measurements of the quantum Hall effect in epitaxial graphene

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