著者

Ogawa Kyohei Nakamura Takashi Terada Yasuhiko Kose Katsumi Haishi Tomoyuki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.23, pp.234101, 2011-06

被引用文献数

81 12

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We have developed the first magnetic resonance (MR) microscope using a high critical-temperature superconducting bulk magnet. The bulk magnet comprises six annular bulk superconductors (60 mm outer diameter, 28 mm inner diameter, 20 mm high) made of c-axis oriented single-domain EuBa2Cu3Oy crystals. The magnet was energized using a superconducting NMR magnet operating at 4.7 T. The inhomogeneity of the trapped magnetic field measured with MR imaging was 3.1 ppm (rms) in the ϕ6.2 mm×9.1 mm cylindrical region. Three-dimensional MR images of a chemically fixed mouse embryo acquired with voxels of (50 μm)3 demonstrated the potential of our system.

著者

Otani Minoru Takagi Yoshiteru Koshino Mikito Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.96, no.24, pp.242504, 2010-06

被引用文献数

25

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Based on first-principle total-energy calculations, we have found that by applying an external electric field it is possible to control the magnetic state of graphite thin film with the rhombohedral stacking arrangement. When exposed to a moderate electric field normal to the film, the surface of a thin film of rhombohedral graphite undergoes a magnetic phase transition from the antiferromagnetic state to the ferromagnetic state. The polarized electron spin is primarily distributed in the bottommost layer of the film, which forms the interface with the negative electrode. The amount of polarized electron spin is calculated to be 0.067 μB/nm2. The ferromagnetic ordering with the characteristic distribution of the polarized electron spin opens the possibility of using graphite thin films in electronic devices with spin degree of freedom.

著者

Koga T. Cronin S. B. Dresselhaus M. S. Liu J. L. Wang K. L.

出版者

American Institute of Physics

雑誌

Applied Physics Letters (ISSN:00036951)

巻号頁・発行日

vol.77, no.10, pp.1490-1492, 2000-09-04

被引用文献数

162

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An experimental proof-of-principle of an enhanced Z3DT (thermoelectric figure of merit) is demonstrated using (001) oriented Si/Ge superlattices. The highest value of the experimental Z3DT at 300 K for a (001) oriented Si(20 Å)/Ge(20 Å) superlattice is 0.1 using κ = 5 Wm−1 K−1, for the in-plane thermal conductivity, which is a factor of seven enhancement relative to the estimated value of Z3DT = 0.014 for bulk Si. The good agreement between experiment and theory validates our modeling approach (denoted as “carrier pocket engineering”) to design superlattices with enhanced values of Z3DT. Proposals are made to enhance the experimental values of Z3DT for Si/Ge superlattices even further. © 2000 American Institute of Physics.

著者

Yoshida Toshiyuki Hashizume Tamotsu

出版者

American Institute of Physics

雑誌

Applied Physics Letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.12, pp.122102, 2012-09-17

被引用文献数

5

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The air-gap capacitance-voltage characteristics of InGaAs surfaces were measured after 1-, 2-, 6-, 9-, and 17-cycle atomic layer deposition (ALD) Al2O3 processing. A high density of mid-gap states was found to be generated and increased during these ALD process steps, while the native oxide component was reduced. On the other hand, the mid-gap state density was drastically reduced after the usual annealing process. The generation of the mid-gap states seemed to be relevant to a non-stoichiometric Al-oxide component associated with a deficit in oxygen atoms, which became re-oxidized during the annealing process.

著者

Masuda Ryo Kobayashi Yasuhiro Kitao Shinji Kurokuzu Masayuki Saito Makina Yoda Yoshitaka Mitsui Takaya Iga Fumitoshi Seto Makoto

出版者

AIP Publishing

雑誌

Applied Physics Letters (ISSN:00036951)

巻号頁・発行日

vol.104, no.8, 2014-02

被引用文献数

24

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電子検出により放射光メスバウアー吸収分光法の測定効率を大幅向上 -さらに多くの元素について放射光メスバウアー分光測定が可能に-. 京都大学プレスリリース. 2014-02-27.

著者

Murakami Katsuhisa Kadowaki Takuya Fujita Jun-ichi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.4, pp.043111, 2013-01

被引用文献数

28 2

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From the analysis of the ratio of D peak intensity to G peak intensity in Raman spectroscopy, electron beam irradiation with energies of 100 eV was found to induce damage in single-layer graphene. The damage becomes larger with decreasing electron beam energy. Internal strain in graphene induced by damage under irradiation is further evaluated based on G peak shifts. The dose-dependent internal strain was approximately 2.22% cm2/mC at 100 eV and 2.65 × 10−2% cm2/mC at 500 eV. The strain induced by the irradiation showed strong dependence on electron energy.

著者

Fujita Jun-ichi Tachi Masashi Murakami Katsuhisa Sakurai Hidehiro Morita Yuki Higashibayashi Shuhei Takeguchi Masaki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.104, no.4, pp.043107, 2014-01

被引用文献数

4

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We found that electron-beam irradiation of sumanene aggregates strongly enhanced their transformation into a graphitic carbon cage, having a diameter of about 20 nm. The threshold electron dose was about 32 mC/cm2 at 200 keV, but the transformation is still induced at 20 keV. The transformation sequence suggested that the cage was constructed accompanied by the dynamical movement of the transiently linked sumanene molecules in order to pile up inside the shell. Thus, bond excitation in the sumanene molecules rather than a knock-on of carbon atoms seems to be the main cause of the cage transformation.

著者

Ito Keita Sanai Tatsunori Zhu Siyuan Yasutomi Yoko Toko Kaoru Honda Syuta Ueda Shigenori Takeda Yukiharu Saitoh Yuji Imai Yoji Kimura Akio Suemasu Takashi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.23, pp.232403, 2013-12

被引用文献数

11 1

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We evaluated electronic structures and magnetic moments in Co3FeN epitaxial films on SrTiO3(001). The experimentally obtained hard x-ray photoemission spectra of the Co3FeN film have a good agreement with those calculated. Site averaged spin magnetic moments deduced by x-ray magnetic circular dichroism were 1.52 μ B per Co atom and 2.08 μ B per Fe atom at 100 K. They are close to those of Co4N and Fe4N, respectively, implying that the Co and Fe atoms randomly occupy the corner and face-centered sites in the Co3FeN unit cell.

著者

Sekimoto S. Watanabe C. Minami H. Yamamoto T. Kashiwagi T. Klemm Richard A. Kadowaki K.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.18, pp.182601, 2013-10

被引用文献数

67 5

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Using a modified mesa structure of high-Tc superconducting Bi2Sr2CaCu2O8+δ with a thin underlaying base superconductor (∼3 μm), the effective working temperature of the continuous and monochromatic terahertz emitter is extended up to 70 K, and the maximum power of ∼30 μW at 0.44 THz is achieved at the relatively high temperature of T b = 55 K in a low bias current retrapping region. The diverging behavior of the intensity occurring at 55 K in the low current regime without hot spot formation may provide us an important clue for the stronger THz radiation from intrinsic Josephson junction devices.

著者

Yonezawa Kouhei Kamioka Hayato Yasuda Takeshi Han Liyuan Moritomo Yutaka

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.17, pp.173901, 2013-10

被引用文献数

9 1

---

By means of femto-second time-resolved spectroscopy, we investigated the carrier formation process against film morphology and temperature (T) in highly-efficient organic photovoltaic, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5- ] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophenediyl]] (PTB7)/[6,6]-phenyl -butyric acid methyl ester solar cells. We found that the carrier formation efficiency ( ) from an absorbed photon is nearly independent of the film morphology, indicating that the internal quantum efficiency ( ) is mainly governed by the carrier transfer efficiency ( ) to the electrodes. The activation energy ( ) of is significantly low, which suggests an extended charge-transfer state around the PTB7/PC70BM interface.

著者

Baba Masakazu Tsurekawa Sadahiro Watanabe Kentaro Du W. Toko Kaoru Hara Kosuke O. Usami Noritaka Sekiguchi Takashi Suemasu Takashi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.14, pp.142113, 2013-09

被引用文献数

29 3

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Potential variations around the grain boundaries (GBs) on the surface in undoped n-BaSi2 epitaxial films on Si(111) and Si(001) were analyzed using Kelvin prove force microcopy. The potentials were higher at GBs than those in the BaSi2 grains on Si(111). The average barrier height was approximately 30 meV at the GBs, indicating that the enhanced potentials repulse photogenerated holes so that the charge carrier recombination can be effectively reduced. In contrast, the potentials were smaller at GBs in the BaSi2 on Si(001), and the average barrier heights were approximately 30 and 50 meV along Si[1–10] and [110], respectively.

著者

Tabata Kenichi Sasaki Takayuki Yamamoto Yohei

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.4, pp.043301, 2013-07

被引用文献数

9

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Organic semiconductor thin films were fabricated by thermal deposition of free-base and metal phthalocyanines under a static magnetic field. A vertical magnetic field enhanced the crystallinity of the edge-on orientation of the phthalocyanine discs, whereas a horizontal magnetic field had a minimal effect on the crystallinity. The major factor for the orientation change is attributed to the diamagnetic anisotropies of π-electrons in the phthalocyanine macrocycles. Field-effect transistors of phthalocyanine films fabricated under a vertical magnetic field exhibited better hole mobilities and on-current values with smaller threshold voltages than those of phthalocyanine films fabricated without a magnetic field.

著者

Benseman T. M. Gray K. E. Koshelev A. E. Kwok W.-K. Welp U. Minami H. Kadowaki K. Yamamoto T.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.02, pp.022602, 2013-07

被引用文献数

107 8

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Stacks of intrinsic Josephson junctions in high-temperature superconductors enable the fabrication of compact sources of coherent terahertz radiation. Here, we demonstrate that multiple stacks patterned on the same Bi2Sr2CaCu2O8+δ crystal can—under optimized conditions—be synchronized to emit high-power THz-radiation. For three synchronized stacks, we achieved 610 μW of continuous-wave coherent radiation power at 0.51 THz. We suggest that synchronization is promoted by THz-waves in the base crystal. We note that synchronization cannot be achieved in all samples. However even in these cases, powers on the 100-μW scale can be generated.

著者

Honda Yuki Maret Elizabeth Hirano Atsushi Tanaka Takeshi Makino Kotaro Hase Muneaki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.22, pp.222109, 2013-06

被引用文献数

1

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We have used a femtosecond pump-probe impulsive Raman technique to explore the polarization dependence of coherent optical phonons in highly purified and aligned semiconducting single-wall carbon nanotubes (SWCNTs). Coherent phonon spectra for the radial breathing modes (RBMs) exhibit a different monochromatic frequency between the film and solution samples, indicating the presence of differing exciton excitation processes. By varying the polarization of the incident pump beam on the aligned SWCNT film, we found that the anisotropy of the coherent RBM excitation depends on the laser wavelength, which we consider to be associated with the resonant and off-resonant behavior of RBM excitation.

著者

Akaba Takahiro Yonezawa Kouhei Kamioka Hayato Yasuda Takeshi Han Liyuan Moritomo Yutaka

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.13, pp.133901, 2013-04

被引用文献数

11

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We investigated carrier formation dynamics in a small-molecular bulk heterojunction solar cell, 2,5-di-(2-ethylhexyl)-3,6-bis-(5″-n-hexy-[2,2′,5′,2″]terthiophen-5-yl)-pyrrolo[3,4-c]pyrrolo-1,4-dione/[6,6]-phenyl C71-butyric acid methyl ester, with low bandgap (Egap ≈ 1.5 eV). The photoinduced absorption (PIA) spectra of the blend film were decomposed into three PIAs, i.e., those due to donor exciton (D*), acceptor exciton (A*), and mobile carrier (D+). The analysis revealed carrier conversion from D* with a conversion time of ∼1.3 ps.

著者

Tsuji Masaki Takahashi Yuki Sakurai Yuki Yomogida Yohei Takenobu Taishi Iwasa Yoshihiro Marumoto Kazuhiro

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.13, pp.133301, 2013-04

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Magnetic interactions and magnetism of high-density charges in a polymer transistor were investigated by electron spin resonance (ESR). The anisotropy of the ESR spectra indicated an edge-on molecular orientation and the existence of two-dimensional magnetic interactions between the spins of the charges, reflecting high charge density. The voltage dependences revealed that the magnetism of charge carriers changed from paramagnetic to nonmagnetic as charge density increased. These results provide insight to the charge transport mechanism of polymer semiconductors with high charge densities.

著者

Konabe Satoru Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.11, pp.113110, 2013-03

被引用文献数

9 5

---

We theoretically investigate the photocurrent generation efficiency of single-walled carbon nanotubes by considering the interplay between exciton many-body effects. We calculate the photocurrent by solving rate equations that incorporate the influences of the two competing processes, multiple exciton generation (MEG) and the Auger recombination (AR) processes. We find that MEG substantially enhances photocurrent generation in spite of the competing AR process. Our calculation shows that the generation efficiency is up to 150% higher than that without MEG.

著者

Khan M. Ajmal Hara K. O. Du W. Baba M. Nakamura K. Suzuno M. Toko K. Usami N. Suemasu T.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.11, pp.112107, 2013-03

被引用文献数

72 15

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B-doped p-BaSi2 layer growth by molecular beam epitaxy and the influence of rapid thermal annealing (RTA) on hole concentrations were presented. The hole concentration was controlled in the range between 1017 and 1020 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1 × 1020 cm−3 were achieved via dopant activation using RTA at 800 °C in Ar. The activation efficiency was increased up to 10%.

著者

Sun Jianhui Zhao Jialong Masumoto Yasuaki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.102, no.5, pp.053119, 2013-02

被引用文献数

49

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We demonstrate the electron transfer (ET) processes from CuInS2/ZnS core/shell quantum dots (QDs) into porous anatase TiO2 films by time-resolved photoluminescence spectroscopy. The rate and efficiency of ET can be controlled by changing the core diameter and the shell thickness. It is found that the ET rates decrease exponentially at the decay constants of 1.1 and 1.4 nm–1 with increasing ZnS shell thickness for core diameters of 2.5 and 4.0 nm, respectively, in agreement with the electron tunneling model. This shows that optimized ET efficiency and QD stability can be realized by controlling the shell thickness.

著者

Cuong Nguyen Thanh Otani Minoru Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.101, no.23, pp.233106, 2012-12

被引用文献数

10 1

---

Based on the first-principles total-energy calculations, we demonstrate the possibility of controlling the band-gap and carrier type of bilayer graphene using ionic molecules. Our calculations suggest that bilayer graphene sandwiched by a pair of cation-anion molecules is a semiconductor with a moderate energy gap of 0.26 eV that is attributable to the strong local dipole field induced by the cation-anion pair. Furthermore, we can control the semiconducting carrier type—intrinsic, p-type, or n-type—of bilayer graphene sandwiched by ionic molecules by changing the cation-anion pair.