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1,402 results on '"Aoyagi, Yoshinobu"'

1. Inter-Layer Screening Length to Electric Field in Thin Graphite Film

Author

Miyazaki, Hisao, Odaka, Shunsuke, Sato, Takashi, Tanaka, Sho, Goto, Hidenori, Kanda, Akinobu, Tsukagoshi, Kazuhito, Ootuka, Youiti, and Aoyagi, Yoshinobu

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Electric conduction in thin graphite film was tuned by two gate electrodes to clarify how the gate electric field induces electric carriers in thin graphite. The graphite was sandwiched between two gate electrodes arranged in a top and bottom gate configuration. A scan of the top gate voltage generates a resistance peak in ambiploar response. The ambipolar peak is shifted by the bottom gate voltage, where the shift rate depends on the graphite thickness. The thickness-dependent peak shift was clarified in terms of the inter-layer screening length to the electric field in the double-gated graphite film. The screening length of 1.2 nm was experimentally obtained., Comment: 5 pages, 4 figures. To be published in Applied Physics Express

Published
2008
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2. Superconducting SET with tunable electromagnetic environment

Author

Watanabe, Michio, Ishibashi, Koji, and Aoyagi, Yoshinobu

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Strongly Correlated Electrons
Abstract

We have studied the environmental effect on superconducting single-electron transistors (S-SETs) by biasing S-SETs with arrays of small-capacitance dc SQUIDs, whose effective impedance can be varied in situ. As the zero-bias resistance of the arrays is increased, Coulomb blockade in the S-SET becomes sharper, and the gate-voltage dependence changes from e-periodic to 2e-periodic. The SQUID arrays could be used as on-chip noise filters., Comment: 2 pages, 3 embedded figures, submitted to LT23 proceedings. Error in Fig. 1 has been fixed

Published
2002
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3. Fast algorithm for calculating two-photon absorption spectra

Author

Kurokawa, Yoshiyuki, Nomura, Shintaro, Takemori, Tadashi, and Aoyagi, Yoshinobu

Subjects
Condensed Matter - Materials Science, Physics - Computational Physics
Abstract

We report a numerical calculation of the two-photon absorption coefficient of electrons in a binding potential using the real-time real-space higher-order difference method. By introducing random vector averaging for the intermediate state, the task of evaluating the two-dimensional time integral is reduced to calculating two one-dimensional integrals. This allows the reduction of the computation load down to the same order as that for the linear response function. The relative advantage of the method compared to the straightforward multi-dimensional time integration is greater for the calculation of non-linear response functions of higher order at higher energy resolution., Comment: 4 pages, 2 figures. It will be published in Phys. Rev. E on 1, March, 1999

Published
1998
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4. Calculating the linear response functions of non-interacting electrons by the time-dependent Schroedinger equation

Author

Iitaka, Toshiaki, Nomura, Shintaro, Hirayama, Hideki, Zhao, Xinwei, Aoyagi, Yoshinobu, and Sugano, Takuo

Subjects
Condensed Matter, Physics - Computational Physics
Abstract

An O(N) algorithm is proposed for calculating linear response functions of non-interacting electrons in arbitray potential. This algorithm is based on numerical solution of the time-dependent Schroedinger equation discretized in space, and suitable to parallel- and vector- computation. Since it avoids O(N^3) computational effort of matrix diagonalization, it requires only O(N) computational effort where N is the dimension of the statevector. This O(N) algorithm is very effective for systems consisting of thousands of atoms, since otherwise we have to calculate large number of eigenstates, i.e., the occupied one-electron states up to the Fermi energy and the unoccupied states with higher energy. The advantage of this method compared to the Chebyshev polynomial method recently developed by Wang (L.W. Wang, Phys. Rev. B49, 10154 (1994);L.W. Wang, Phys. Rev. Lett. 73, 1039 (1994)) is that our method can calculate linear response functions without any storage of huge statevectors on external storage. Therefore it can treat much larger systems., Comment: to be published in Phys.Rev.E56(1). 19 pages, 8 figures, more information at http://espero.riken.go.jp

Published
1997
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6. Formation of conductive AlN buffer layer using spontaneous via-holes and realization of vertical AlGaN Schottky diode on a Si substrate.

Author

Kurose, Noriko and Aoyagi, Yoshinobu

Subjects
*SILVER nitrate, *METAL organic chemical vapor deposition, *EPITAXY, *SCHOTTKY barrier diodes, *ALUMINUM-silicon alloys
Abstract

A conductive AlN epitaxial layer is successfully realized by spontaneously forming via-holes filled with n-AlGaN inside an AlN buffer layer on a Si substrate. The via-holes are found to originate from the formation of an Al–Si alloy, produced from a small amount of Al supplied to the Si substrate at the initial stage of the crystal growth of the n-AlN buffer layer using metal organic chemical vapor deposition and successive selective growth of n-AlN on the Si surface. The via-holes are filled with conductive n-AlGaN by successive epitaxial growth of n-AlGaN, making the insulating n-AlN buffer layer conductive. The vertical conductivity through this n-AlN buffer layer is enhanced more than 540 times compared with an n-AlN buffer layer without via-holes. Using this conductive n-AlN buffer layer on the Si substrate, we successfully fabricated a vertical n-AlGaN Schottky diode on the Si substrate for the first time. [ABSTRACT FROM AUTHOR]

Published
2019
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16. Optical properties of GaN quantum dots

Author

Ramvall, Peter, Riblet, Philippe, Nomura, Shintaro, Aoyagi, Yoshinobu, and Tanaka, Satoru

Subjects
Lasers -- Research, Quantum theory -- Usage, Physics
Abstract

The optical properties of GaN quantum dots grown using metalorganic vapor phase epitaxy, were studied.

Published
2000

17. The optically active center and its activation process in Er-doped Si thin film produced by laser ablation

Author

Ishii, Masashi, Ishikawa, Tetsuya, Ueki, Tatzuo, Komuro, Shuji, Morikawa, Takitaro, Aoyagi, Yoshinobu, and Oyanagi, Hiroyuki

Subjects
Erbium -- Research, Silicon -- Research, Thin films -- Research, Physics
Abstract

A study was conducted to analyze the local structure of erbium-doped silicon generated by the laser ablation method. Er L(sub III)-edge x-ray absorption fine structure analysis was carried out. The Si target supported two types of local structures. Experimental results indicated that the local structure of the optically active center support strong photoluminescence has a C4v point group that is distorted from the O(sub H) symmetry.

Published
1999

19. InGaAs/GaAs quantum nanostructure fabrication on GaAs (111) A vicinal substrates by atomic layer epitaxy

Author

Lee, Jeong-Sik, Isshiki, Hideo, Sugano, Takuo, and Aoyagi, Yoshinobu

Subjects
Epitaxy -- Methods, Nanotechnology -- Research, Physics
Abstract

The atomic layer epitaxy (ALE) selective growth on the (111)A vicinal surface affects high growth selectivity as well as the size and shape control of quantum nanostructures. The ALE technique was used in the fabrication of InGaAs/GaAs quantum wire and dots. Wire structures were successfully fabricated on the vicinal surface using the ALE approach, while quantum dot structures were fabricated on the step region.

Published
1998

20. Reflection-wavelength control method for layer-by-layer controlled x-ray multilayer mirrors

Author

Ishii, Masashi, Iwai Sohach, Ueki, Tatzuo, and Aoyagi, Yoshinobu

Subjects
Thin films, Multilayered -- Research, Astronomy, Physics
Abstract

A reflection-wavelength control method for a layer-by-layer controlled x-ray multilayer mirror without interface roughness is proposed. The reflection wavelength of the multiperiodic mirror is found to be simply determined by a combination ratio of periodic layers. Multiperiodic x-ray mirrors with reflectance wavelengths at 3.374 nm (C VI 1s-2p) and 3.950 nm (Ca XVIII 3d-5f) are successfully design. Key words: Multiperiodic mirror, layer by layer, phase compensation.

Published
1997

25. Carrier dynamics in oxidized porous silicon

Author

Komuro, Shuji, Kato, Takashi, Morikawa, Takitaro, O'Keeffe, Patrick, and Aoyagi, Yoshinobu

Subjects
Silicon -- Spectra, Photoluminescence -- Measurement, Energy levels (Quantum mechanics) -- Observations, Physics
Published
1996

28. Two-dimensional versus three-dimensional excitons in wide GaAs quantum wells

Author

Kusano, Jun-ichi, Bauer, Gerrit E.W., and Aoyagi, Yoshinobu

Subjects
Gallium arsenide -- Research, Quantum wells -- Research, Exciton theory -- Research, Luminescence -- Research, Physics
Abstract

Photoluminescence and reflectance spectroscopy facilitate the analysis of exciton motion in GaAS/AlGaAs double heterostructures and are aimed at identifying the transition process from a two-dimensional exciton in quantum cells to a three-dimensional exciton in a thin film. The dependence of a quasi-three-dimensional exciton on quantization of the spatial dispersion in the quantum wells reveals exciton coherence length to be greater than 4020 angstroms.

Published
1994

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