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Nishinomiya, Japan

Araki K.,Yokohama National University | Minami Y.,Yokohama National University | Dao T.D.,Japan International Center for Materials Nanoarchitectonics | Nagao T.,Japan International Center for Materials Nanoarchitectonics | And 8 more authors.
Springer Proceedings in Physics | Year: 2015

We investigated nonlinear carrier response of semi-metal bismuth under intense terahertz pulse illumination. By applying the intense terahertz field, the transmittance increases more than 10%, indicating an increase of the effective mass. © Springer International Publishing Switzerland 2015. Source


Maekawa K.,Yokohama National University | Sato K.,Yokohama National University | Minami Y.,Yokohama National University | Katayama I.,Yokohama National University | And 5 more authors.
Springer Proceedings in Physics | Year: 2015

Coherent phonons in single-walled metallic carbon nanotubes were measured under the application of a gate voltage through ionic liquid. We found that the frequencies, amplitudes and phases of the phonons strongly depend on the voltage. © Springer International Publishing Switzerland 2015. Source


Kitajima M.,Japan National Defense Academy | Kitajima M.,LxRay Co. | Narushima T.,Japan Institute for Molecular Science | Kurashina T.,University of Tsukuba | And 5 more authors.
Journal of Physics Condensed Matter | Year: 2013

We report the real-time observation of the stress change during sub-nanometer oxide growth on the Si(100) surface. Oxidation initially induced a rapid buildup of tensile stress up to -1.9 × 108 N m -2 with an oxide thickness of 0.25 nm, followed by gradual compensation by a compressive stress. The compressive stress saturated at 5 × 107 N m-2 for an oxide thickness of 1.2 nm. The analysis, assisted by theoretical study, indicates that the observed initial tensile stress is caused by oxygen bridge-bonding between the Si dimers. Atomistic model calculations considering mutually orthogonal orientations of the Si(100) surface structure reproduce the stress inversion from the tensile to the compressive side. © 2013 IOP Publishing Ltd. Source


Yoshioka K.,Yokohama National University | Minami Y.,Yokohama National University | Shudo K.-I.,Yokohama National University | Dao T.D.,Japan International Center for Materials Nanoarchitectonics | And 10 more authors.
Nano Letters | Year: 2015

Improved control over the electromagnetic properties of metal nanostructures is indispensable for the development of next-generation integrated nanocircuits and plasmonic devices. The use of terahertz (THz)-field-induced nonlinearity is a promising approach to controlling local electromagnetic properties. Here, we demonstrate how intense THz electric fields can be used to modulate electron delocalization in percolated gold (Au) nanostructures on a picosecond time scale. We prepared both isolated and percolated Au nanostructures deposited on high resistivity Si(100) substrates. With increasing the applied THz electric fields, large opacity in the THz transmission spectra takes place in the percolated nanostructures; the maximum THz-field-induced transmittance difference, 50% more, is reached just above the percolation threshold thickness. Fitting the experimental data to a Drude-Smith model, we found furthermore that the localization parameter and the damping constant strongly depend on the applied THz-field strength. These results show that ultrafast nonlinear electron delocalization proceeds via strong electric field of THz pulses; the intense THz electric field modulates the backscattering rate of localized electrons and induces electron tunneling between Au nanostructures across the narrow insulating bridges without any material breakdown. © 2015 American Chemical Society. Source


Minami Y.,Yokohama National University | Takeda J.,Yokohama National University | Dao T.D.,Japan International Center for Materials Nanoarchitectonics | Dao T.D.,Japan Science and Technology Agency | And 8 more authors.
Applied Physics Letters | Year: 2014

Linear and nonlinear electron dynamics of polycrystalline gold (Au) ultrathin films with thicknesses ranging from 1.4 to 5.8 nm were investigated via transmittance terahertz (THz) spectroscopy with intense electric field transients. We prepared ultrathin films with low surface roughness formed on a Si-(7 ×7) reconstructed surface, leading to the observation of monotonic decrease in THz transmittance with respect to film thickness. Furthermore, at all tested thicknesses, the transmittance decreased nonlinearly by 10%-30% with the application if high-intensity THz electric fields. Based on a Drude-model analysis, we found a significant decrease in the damping constant induced by the THz electric field, indicating that electrons are driven beyond the polycrystalline grain boundaries in Au thin films, and consequently leading to the suppression of the electron-boundary scattering rate. © 2014 AIP Publishing LLC. Source

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