Jun Ogi

Experimental Observation of Enhanced Electron–Phonon Interaction in Suspended Si Double Quantum Dots

Silicon-based suspended double quantum dots (SDQDs) were fabricated to study and control the strength of the electron–phonon interaction. A distinctive and large inelastic tunneling was observed in single-electron transport measurement and well explained by the emission of phonons that interact strongly with electrons owing to the phonon modulation in the suspended film. The first time observation of the enhancement of the electron–phonon interaction in Si SDQDs as well as the good agreement between the experimental results and the theoretical simulations are encouraging preliminary results that allow us to envision the observation of the tailoring of the electron–phonon interaction in SDQDs.

Suspended Quantum Dot Fabrication on a Heavily Doped Silicon Nanowire by Suppressing Unintentional Quantum Dot Formation

We aim at embedding a quantum dot on a suspended nanowire by solving the problem of unintentional quantum dot formation, which exacerbates in a suspended nanowire. The origin of this worsening is the higher potential barrier presumably owing to the enhancement of random-dopant-induced potential fluctuation and/or higher degree of surface roughness and surface trapped charges on suspended nanowires. The higher barrier was successfully decreased by adopting a higher doping concentration as well as wider constriction patterns. Consequently, we can control the quantum dot formation in the suspended nanowire and successfully defined a single-quantum dot by patterning the double constrictions on the heavily doped suspended nanowire.

Direct observation of subband structures in (110) PMOSFETs under high magnetic field: Impact of energy split between bands and effective masses on hole mobility

The band structures and carrier transport in (110) pFETs are thoroughly studied over a wide temperature range under high magnetic fields. In (110) pFETs, the degenerate hole bands in bulk Si are separated into the higher energy band (H band) and the lower energy band (L band). The energy difference between these bands is experimentally evaluated. The effective masses of each band are directly obtained from the Shubnikov-de Haas (SdH) oscillation analysis. It is demonstrated that mobility in the higher energy band is worse than that in the lower energy band, resulting in sharp mobility drop at higher surface carrier concentrations (Ns) and a clear hump in Id-Vg characteristics at low temperatures of less than 20 K. In order to further enhance mobility in (110) pFETs, the increase in the energy split between H and L bands is important.

Scaled nanoelectromechanical (NEM) hybrid devices

This paper overviews recent attempts at co-integrating nano-electro-mechanical systems (NEMS) with nanoelectronic devices aiming to add more functionalities to conventional Si devices in ‘More-than-Moore’ domain and also explore novel physical principles in ‘Beyond CMOS’ domain.

Scaled silicon nanoelectromechanical (NEM) hybrid systems

In this paper we overview recent attempts at co-integrating silicon nano-electro-mechanical systems (NEMS) with nanoelectronic devices aiming to add more functionalities to conventional electronic devices in ‘More-than-Moore’ domain and also explore novel operating principles in ‘Beyond CMOS’ domain.

Co-integration of silicon nanodevices and NEMS for advanced information processing

In this paper we present our recent attempts at developing the advanced information processing devices by integrating nano-electro-mechanical (NEM) structures into conventional silicon nanodevices. Firstly, we show high-speed and nonvolatile NEM memory which features a mechanically-bistable floating gate is integrated onto MOSFETs. Secondly we discuss hybrid systems of single-electron transistors and NEM structures for exploring new switching principles.

Anomalous suppression of single-electron tunnelling observed for Si nanobridge transistors with a suspended quantum dot cavity

Recent advance on fabricating silicon nano electromechanical systems (NEMS) has enabled us to study single-electron tunnelling through nanometerscale suspended structures with restrained coupling to the environment. In particular, a suspended quantum dot cavity structure built on a Si nanobridge provides an ideal system to explore the interaction of single electrons with tailored phonon spectrum in the cavity which is acoustically isolated from the Si substrate. Such a system has recently become of great interest in terms of studying physics of decoherence mechanisms for quantum bits and also revealing ultimate energy dissipation process in Si nanostructures.Here, we report on anomalous suppression of single-electron tunnelling observed for a low source-to-drain region. These characteristics are attributable to the enhanced interaction between tunneling electrons and cavity phonons.