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Single-Electron-Resolution Noise Analysis and Application Using High-Sensitivity Charge Sensor
Katsuhiko Nishiguchi et al
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DOI: 10.22661/AAPPSBL.2019.29.3.04

Single-Electron-Resolution Noise Analysis and Application Using High-Sensitivity Charge Sensor


* E-mail address: katsuhiko.nishiguchi.vu@hco.ntt.co.jp


We introduce an analysis of thermal noise using a high-sensitivity charge sensor. Since the sensor is based on a Si field-effect transistor whose channel size is approximately 10 nm, the sensor exhibits sufficiently high sensitivity to detect single-electron motion even at room temperature. By connecting this sensor to a small capacitor comprising dynamic random access memory, thermal noise in the capacitor can be monitored in real time with single-electron resolution. Such real-time monitoring reveals that when the capacitor is sufficiently small that the charging energy for storing one electron in the capacitor is greater than the thermal energy, the thermal noise is suppressed and enhanced. This represents a deviation from the law of energy equipartition. In addition to this noise analysis, we present a successful demonstration of power generation using an analogy of Maxwell's demon that detects and manipulates single-electron motion, which should accelerate research in the field of thermodynamics. These experimental results show that the high-sensitivity charge sensor can function as a superior platform for microscopic analysis of noise, small electronic devices, and thermodynamics as well as a demonstration of theoretical expectation in basic research.


Data processing circuits comprise a huge number of Si field-effect transistors (FETs) and their miniaturization has increased circuit performance. FETs have also been used as a signal amplifier or sensor for various kinds of applications such as memory circuits, image sensors, and chemical sensors. Si-FET sensors are advantageous due to their superior integration and miniaturization capabilities. In particular, the currently employed miniaturization technique established for data processing circuits achieves a nanometer-scale structure enabling a sufficiently high level of sensor sensitivity [1, 2] to detect an extremely small number of objects including proteins [3, 4], DNA [5], and ultimately a single charge [6]. Such improvement in the sensor sensitivity provides various merits to not only practical applications but also basic research. Some such merits for practical applications are high-resolution signal detection, fast sensing, and highly dense integration. Up-coming applications such as the quantum computers and quantum key distributions have also relied on highly sensitive sensors with single-electron and single-photon resolution. In the fields of basic research, high-sensitivity sensors have played important roles in revealing new phenomena and physics, and are vital to academics and applications in the future.

In this paper, we introduce analysis on electric noise using a Si-FET-based sensor. Since the sensor is sufficiently small to detect single electrons, noise analysis can be carried out with single-electron. Although single-electron detection reported elsewhere have been carried out at low temperature, miniaturization of the Si-FET-based sensor allows room-temperature operation. Additionally, a unique application taking advantage of single-electron detection, i.e., Maxwell's demon, is also shown.


Single-electron-resolution electric-noise analysis is carried out using a Si-FET-based sensor integrated with dynamic random access memory (DRAM) comprising one FET and one storage capacitor (SC) as shown in Fig. 1 [6]. By controlling the FET with word and bit lines, electrons are stored in or released from the SC and absence/existence of electrons in the SC is usually represented as one bit of information. Since the resistance of the FET is not infinite even in its off state, electrons are randomly shuttled between the SC and bit line due to thermal energy, which causes the thermal noise in the SC. In our analysis, this electron shuttling, i.e., thermal noise, is monitored with single-electron resolution using the sensor. Electrons in the SC modulate the current flowing through the sensor due to repulsive force between the electrons in the SC and those in the sensor channel. A key point for single-electron monitoring is the degree of current modulation, dImodulation. Following conventional noise analysis, we consider voltage noise Vnoise instead of electron shuttling. In the most likely case