Showing papers by "Myung-Ho Bae published in 2020"

Precision current measurement with thermal-drift-minimized offset current for single-parameter electron pumps based on gate-switching technique

Abstract: Single-parameter single-electron pumps (SEPs) based on a quantum dot have been suggested as promising devices to realize the new definition of the unit of current, the ampere, where quantized current produced from the SEP device is only defined by the elementary charge e and applied external radiofrequency (rf), f, i.e., I = ef. The conventional method to eliminate offset signals in the precision current measurement of pump current has been to measure the current difference between the pump-on and pump-off states. To date, the rf-on and rf-off method has been used to pump between its on and off states. However, this method inevitably induces alternating rf-heating effects and varying temperatures of the device environment, possibly leading to a thermal drift of the offset current. In the current work, we developed a new gate-switching technique that can alternate the pump on and off states while maintaining a constant rf-on state, resulting in a more stable system temperature. Using the gate-switching technique, we achieved a temperature-stabilized environment and performed a precision current measurement with sub-parts per million uncertainty.

GaAs/AlGaAs-based single-electron pumps developed in KRISS

Abstract: A single-electron pump based on a quantum dot is a promising candidate to realize the quantum current standard based on the new SI definition. In order to develop the quantum current standard, we fabricated two different types of single electron pumps based on GaAs/AlGaAs heterostructures by using KRISS nanofabrication facility. From the measurement results, we successfully observed the quantized current steps from the two differently designed pump devices.

Study on Cold-Finger 3 He Cryostat for Precision Measurements of Quantum Hall Resistance and Single-Electron Pump Current

Abstract: The performance of our newly constructed cold-finger cryostat is investigated for the precision measurement of quantum Hall resistance (QHR) and single-electron pump (SEP) current. The cryostat is featured by a vacuum sealed sample chamber that is attached to the 0.3 K-plate inside the inner vacuum can. The nominal base temperature of the sample chamber was 0.4 K. However, the electron temperature estimated with a single-electron transistor was approximately 0.6 K. Precision evaluation of a GaAs QHR device shows that the quantized Hall resistance is equivalent to the nominal value of $h/2e^{2}$ within one part in 108. The Allan deviation data for the SEP current is analyzed to be greater than those obtained from SEP in a wet 3He cryostat at Korean Research Institute of Standards and Science.

Current-reversal technique for single-parameter electron pumps

Abstract: We developed a current-reversal operation method for single-parameter electron pumps, based on cryo-gate switches located between the ohmic contacts and quantum dot. The current reversal mode provided an enhanced signal-to-noise ratio, resulting in a reduction of the measurement time to reach the same relative measurement uncertainty, compared to a conventional unipolar current measurement method.