Room-temperature single-electron transfer and detection
with silicon nanodevics

Katsuhiko Nishiguchi, Akira Fujiwara, Yukinori Ono, Hiroshi Inokawa, and *Yasuo
Physical Science Laboratory, *Present address: Hokkaido university

 Single-electron devices (SEDs) have great attention because of their ultra-low power consumption. The single-electron turnstile, which transfers electrons one by one, is a member of the SED family and is a promising device for an architecture which treats one electron. This architecture requires precise control of electron movement and accurate detection of single electrons. Although various studies demonstrated these two key points, the operation temperature has remained quite low because the devices were not small enough to prevent thermal energy disturbing electron movement and to gain sufficient sensitivity for single-electron detection.
 We thus proposed the silicon nanodevices which can transfer and detect single electrons and fabricated them on a silicon-on-insulator (SOI) (Fig. 1) [1]. The single-electron turnstile is composed of two wire-FETs. A single-electron box (SEB) is electrically defined between FETs. By turning on FET1 and FET2 alternately, the single electron is transferred to the memory node (MN) through the SEB (the inset of Fig. 2). One transfer cycle for injecting the single electron in the MN is composed of four steps shown in the inset of Fig. 2 [2]. By repeating the transfer cycles, the electrons are transferred one by one. The single electrons transferred into the MN are detected by an electrometer capacitively coupled to the MN. The electrometer is carefully positioned close to the MN so that the sensitivity of the electrometer is high enough to detect single electrons in the MN [3].
 Figure 2 shows changes in the electrometer current when transfer cycle was repeated. Current change per transfer cycle was caused by one electron transfer. The size reduction of the SEB and optimized operating conditions allowed the single-electron transfer and detection at room temperature. The present device using FETs for the electron transfer and storage achieves high-speed transfer (<10ns) and long retention (>104s). We also demonstrated that the present device could serve as a multi-level (5 bit) single-electron memory [1].
[1] K. Nishiguchi, et al., International Electron Devices Meeting (IEDM) (2004) 199.
[2] A. Fujiwara, et al., Appl. Phys. Lett. 84 (2004) 1323.
[3] K. Nishiguchi, et al., Appl. Phys. Lett. 85 (2004) 1277.
view of the single-erectron turnstile.
Fig. 2. Single-erectron transfer and derection

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