著者

Asai Hidehiro Tachiki Masashi Kadowaki Kazuo

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.11, pp.112602, 2012-09

被引用文献数

23

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We propose a THz patch antenna, in which THz ac current is fed by intrinsic Josephson junctions (IJJs). The radiation power of the antenna for three different feed positions is calculated using the finite-difference time-domain method. We predict that the antenna will radiate sub-milliwatt terahertz waves with high radiation efficiency of over 20%. The maximum radiation power will depend on the position of the feed. We also show that the radiation characteristics of the antenna are described well by the equivalent inductance-capacitance-resistance circuit model.

著者

Peng D. L. Sumiyama Kenji Yamamuro S. Hihara Takehiko Konno T. J. ヒハラ タケヒコ スミヤマ ケンジ 隅山 兼治 日原 岳彦 Sumiyama K. Hihara T.

出版者

American Institute of Physics

雑誌

APPLIED PHYSICS LETTERS (ISSN:00036951)

巻号頁・発行日

vol.74, no.1, pp.76-78, 1999-01-04

被引用文献数

33

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We have studied electrical conductivity, σ, and magnetoresistance in a CoO-coated monodispersive Co cluster assembly fabricated by a plasma-gas-aggregation-type cluster beam deposition technique. The temperature dependence of σ is described in the form of log σ vs 1/T for 7<T<80 K. The magnetoresistance ratio (ρ0-ρ3T)/ρ0 increases sharply with decreasing temperature below 25 K: from 3.5% at 25 K to 20.5% at 4.2 K. This marked increase (by a factor of 6) is much larger than those observed for conventional metal-insulator granular systems. These results are ascribed to the Coulomb blockade effect in the monodispersed cluster assemblies.

著者

Toko K. Kurosawa M. Saitoh N. Yoshizawa N. Usami N. Miyao M. Suemasu T.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.7, pp.072106, 2012-08

被引用文献数

88 20

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(111)-oriented Ge thin films on insulators are essential for advanced electronics and photovoltaic applications. We investigate Al-induced crystallization of amorphous-Ge films (50-nm thickness) on insulators focusing on the annealing temperature and the diffusion controlling process between Ge and Al. The (111)-orientation fraction of the grown Ge layer reaches as high as 99% by combining the low-temperature annealing (325 °C) and the native-oxidized Al (AlOx) diffusion-control layer. Moreover, the transmission electron microscopy reveals the absence of defects on the Ge surface. This (111)-oriented Ge on insulators promises to be the high-quality epitaxial template for various functional materials to achieve next-generation devices.

著者

Yamada Yasuhiro Kanemitsu Yoshihiko

出版者

American Institute of Physics

雑誌

Applied Physics Letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.13, 2012-09-27

被引用文献数

232

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二酸化チタン中の光キャリアの振る舞いを解明 -高効率太陽電池の実現に期待-. 京都大学プレスリリース. 2012-09-28.

著者

Kondo Takahiro Kato Hiroyuki S. Bonn Mischa Kawai Maki

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.127, no.9, pp.094703, 2007-09

被引用文献数

41 20

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The deposition and the isothermal crystallization kinetics of thin amorphous solid water (ASW) films on both Ru(0001) and CO-precovered Ru(0001) have been investigated in real time by simultaneously employing helium atom scattering, infrared reflection absorption spectroscopy, and isothermal temperature-programmed desorption. During ASW deposition, the interaction between water and the substrate depends critically on the amount of preadsorbed CO. However, the mechanism and kinetics of the crystallization of ~50 layers thick ASW film were found to be independent of the amount of preadsorbed CO. We demonstrate that crystallization occurs through random nucleation events in the bulk of the material, followed by homogeneous growth, for solid water on both substrates. The morphological change involving the formation of three-dimensional grains of crystalline ice results in the exposure of the water monolayer just above the substrate to the vacuum during the crystallization process on both substrates.

著者

Chen Zhen Nozaki Ryusuke

出版者

American Institute of Physics

雑誌

Journal of Chemical Physics (ISSN:00219606)

巻号頁・発行日

vol.136, no.24, pp.244505, 2012-06-28

被引用文献数

16

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We report here a broadband dielectric spectroscopy study on an ionic liquid microemulsion (ILM) composed of water, Triton X-100 (TX-100), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). It is found that the phase behavior of this ILM can be easily identified by its dielectric response. The dielectric behavior of the ILM in the GHz range is consistent with that of TX-100/water mixtures with comparable water-to-TX-100 weight ratio. It consists of the relaxations due to ethylene oxide (EO) unit relaxation, hydration water dynamics, and/or free water dynamics. The water content dependence of the EO unit relaxation suggests that this relaxation involves dynamics of hydration water molecules. In the IL-in-water microemulsion phase, it is found that bmimPF6 molecules are preferentially dissolved in water when their concentration in water is lower than the solubility. An additional dielectric relaxation that is absent in the TX-100/water mixtures is observed in the frequency range of 10^[7]-10^[8] Hz for this ILM. This low-frequency relaxation is found closely related to the bmimPF6 molecule and could be attributed to the hopping of its cations/anions between the anionic/cationic sites.

著者

Suzuki Motofumi Hamachi Kenji Hara Hideki Nakajima Kaoru Kimura Kenji Hsu Chia-Wei Chou Li-Jen

出版者

American Institute of Physics

雑誌

Applied Physics Letters (ISSN:00036951)

巻号頁・発行日

vol.99, no.22, 2011-12

被引用文献数

13

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We have demonstrated that the vapor-liquid-solid (VLS) growth of Ge nanowhiskers is significantly enhanced by high-temperature glancing angle deposition (HT-GLAD). At the substrate temperature of 420 °C, the Ge nanowhiskers grow on the sample deposited at the deposition angle of α = 85°, whereas no long nanowhisker grows on the samples deposited at α ≤ 73°. The kinetic growth model that takes into account the directional incidence of the vapor flux agrees with the experimental results and suggests that the atoms deposited on the side surface of the nanowhiskers play an essential role in the HT-GLAD assisted VLS growth. Supplying the atoms on the side surface of the nanowhiskers is expected to accelerate the growth of the nanowhiskers in any vapor phase growth methods, such as molecular beam epitaxy and chemical vapor deposition.

著者

Kim Young-ho Zhao Jianwei Uosaki Kohei

出版者

American Institute of Physics

雑誌

Journal of Applied Physics (ISSN:00218979)

巻号頁・発行日

vol.94, no.12, pp.7733-7738, 2003-12-15

被引用文献数

8

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Nanosized patterns of tantalum oxide were fabricated on a tantalum substrate by applying a potential pulse utilizing current sensing atomic force microscopy (CSAFM). The dimensions of the dots were strongly dependent on the bias applied, scan rate, and potential pulse duration. By controlling these variables, the minimum size nanodots with full width at half maximum of 35 nm was achieved. Immediately after pattern formation, the electrical properties of the Ta oxide nanodots were measured using CSAFM. The charge transport at the CSAFM tip and the nanosized Ta oxide dot can be described by Poole–Frenkel type conduction. The relative dielectric constant of the nanosized Ta2O5 dots was calculated to be 17.8–24.3, showing that the quality of the oxide was high. In addition, by controlling the substrate bias applied, pulse duration, and tip scan speed, nanosized Ta oxide lines with the desired dimensions were prepared.