Related Experiment Video
Updated: Jan 20, 2026
Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures
Published on: June 28, 2017
Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic
G J Verbiest1, H Janssen1, D Xu1
1JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany, EU.
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.
Related Concept Videos
09:50Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures
09:38Measuring Changes in Brain Endothelial Barrier Integrity with Two Impedance-based Biosensors in Response to Cancer Cells and Cytokines
08:56Capacitance
This experiment will use commercial capacitors and a parallel plate capacitor to demonstrate the concept of capacitance. A capacitor stores opposite charges on two conductors, for example two opposite metal plates, leading to a potential difference (voltage drop) between the two conductors. The amount of charge on each conductor is proportional to this voltage drop, with...
06:00Biological Samples Preparation for Speciation at Cryogenic Temperature using High-Resolution X-Ray Absorption Spectroscopy
10:04Magnetic Fields
Magnetic fields can be generated by moving charges, such as an electrical current. The magnetic field generated by a current can be calculated from the Maxwell equation. In addition, magnetic objects such as bar magnets can also generate magnetic fields due to microscopic dynamics of charges inside the material. Magnetic fields will exert magnetic force on other moving...
01:27Magnetic Fields
A magnetic field is defined by the force that a charged particle experiences...