arXiv subjects

Jürgen Schurr

Publications and source records attributed to Jürgen Schurr.

3 recordsLinked to original sources

arXiv2024

Measurement of Resistance Standards by a Precision LCR Meter at Frequencies up to 2 MHz

We report on two-terminal-pair and four-terminal-pair test measurements of a 10-kohm resistance standard by means of a commercial precision LCR meter at frequencies up to 2 MHz. In the case of a two-terminal-pair configuration, we demonstrate that the effect of 2.5 m long measuring cables, which are inevitable for some special applications, can be corrected in the whole frequency range up to 2 MHz with an uncertainty of 9E-6 (k = 1) relative to the dc resistance value. Furthermore, the systematic effects of the LCR meter were investigated. Though distinctly larger than the resolution of the LCR meter, these effects are accurately reproducible. As such it should be possible in the future to calibrate the LCR meter against a well-known calculable high-frequency resistance standard with an uncertainty close to the few-parts-per-million type-A uncertainty of the LCR meter.

physics.ins-det↗

arXiv2024

Resistance standards with calculable, nearly negligible AC-DC difference at frequencies up to 2 MHz for the calibration of precision LCR meters

We have developed novel impedance standards based on thin-film surface-mount-device (SMD) resistors. Due to the small dimensions of such resistors, the quantities determining their frequency dependence are very small and can be either measured or numerically calculated. A series connection of thin-film SMD resistors allows us to further improve the DC and the AC properties. The nominal resistance value of our application is 12.906 kohm but other values are just as possible. At frequencies up to 2 MHz, the calculated frequency dependence amounts to only a few parts per million of the DC value, which is about four orders of magnitude smaller than for all conventional calculable AC-DC resistors having a similar nominal DC value. To measure the frequency dependence, we use a precision inductance-capacitance-resistance (LCR) meter at frequencies up to 2 MHz that has a reproducibility of a few parts per million but a systematic uncertainty which is specified by the manufacturer to increase from 300 parts per million in the lower frequency range to 3000 parts per million at 2 MHz. Measurements of two very different SMD-based resistance standards allow verification of the model calculation as well as the calibration of the precision LCR meter, both with a relative uncertainty of a few parts per million in the whole frequency range. This boost in precision enables new applications in this frequency range such as the verification of conventional calculable resistance standards, the calibration of impedance standards, and future measurements of the quantum Hall resistance.

physics.ins-det↗

arXiv2016

Nonequilibrium mesoscopic conductance fluctuations as the origin of 1/f noise in epitaxial graphene

We investigate the 1/f noise properties of epitaxial graphene devices at low temperatures as a function of temperature, current and magnetic flux density. At low currents, an exponential decay of the 1/f noise power spectral density with increasing temperature is observed that indicates mesoscopic conductance fluctuations as the origin of 1/f noise at temperatures below 50 K. At higher currents, deviations from the typical quadratic current dependence and the exponential temperature dependence occur as a result of nonequilibrium conditions due to current heating. By applying the theory of Kubakaddi [S. S. Kubakaddi, Phys. Rev. B 79, 075417 (2009)], a model describing the 1/f noise power spectral density of nonequilibrium mesoscopic conductance fluctuations in epitaxial graphene is developed and used to determine the energy loss rate per carrier. In the regime of Shubnikov-de Haas oscillations a strong increase of 1/f noise is observed, which we attribute to an additional conductance fluctuation mechanism due to localized states in quantizing magnetic fields. When the device enters the regime of quantized Hall resistance, the 1/f noise vanishes. It reappears if the current is increased and the quantum Hall breakdown sets in.

cond-mat.mes-hall↗