- 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
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.
1 0 0 0 OA Electronic structures and magnetic moments of Co3FeN thin films grown by molecular beam epitaxy
- 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
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
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
- Katanuma I. Sato S. Okuyama Y. Kato S. Kubota R.
- 出版者
- American Institute of Physics
- 雑誌
- Physics of plasmas (ISSN:1070664X)
- 巻号頁・発行日
- vol.20, no.11, pp.112107, 2013-11
A particle simulation of an interchange instability was performed by taking into account the ion finite Larmor radius (FLR) effects. It is found that the interchange instability with large FLR grows in two phases, that is, linearly growing phase and the nonlinear phase subsequent to the linear phase, where the instability grows exponentially in both phases. The linear growth rates observed in the simulation agree well with the theoretical calculation. The effects of FLR are usually taken in the fluid simulation through the gyroviscosity, the effects of which are verified in the particle simulation with large FLR regime. The gyroviscous cancellation phenomenon observed in the particle simulation causes the drifts in the direction of ion diamagnetic drifts.
1 0 0 0 OA Favorable electronic structure for organic solar cells induced by strong interaction at interface
- 著者
- Wang Shenghao Sakurai Takeaki Hao Xia Fu Wei Masuda Shigeru Akimoto Katsuhiro
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.114, no.18, pp.183707, 2013-11
- 被引用文献数
- 8 2
To clarify the role of buffer layer in organic solar cells (OSCs), the electronic properties of bathocuproine (BCP)/Mg interface were systematically investigated by using ultraviolet photoemissions spectroscopy, high-resolution X-ray photoemission spectroscopy, angle-resolved X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results show there are gap states at the interface, which are caused by the interaction between BCP and Mg. The formation of Mg-N bond was found at the interface. The NEXAFS measurements show that BCP molecules for 1-2 monolayers are lying-down on the substrate, whereas orient randomly for thick BCP layer. It was supposed that the gap states and the highly-ordered orientation of thin BCP layer are the reasons for improving the performance of OSC with BCP buffer layer and low work function metal cathode.
- 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
- Sasaki Shuichi Yagi Ichimasa Murakami Masato
- 出版者
- American Institute of Physics
- 雑誌
- Journal of Applied Physics (ISSN:00218979)
- 巻号頁・発行日
- vol.95, no.4, pp.2090-2093, 2004-01-01 (Released:2016-05-17)
- 被引用文献数
- 9
An iron ball floats in midair in a plastic box when several iron balls were attracted by a permanentmagnet. A complex interaction between magnetized sphere materials and a lifting magnet enabledthe suspension of an iron ball. The balls in the first row are simply attracted by the lifting magnet.The ball in the second row is also attracted by the lifting magnet, however, due to the repulsiveforces exerted from the balls sitting above, it can float in midair. We also found that there are twostable positions for the ball to float. The floating ball could be transported from one equilibriumposition to another by simply rotating the lifting magnet. This will make it possible to construct anoncontact load transport device.
- 著者
- Amano Masakazu Yamamura Yasuhisa Sumita Masato Yasuzuka Syuma Kawaji Hitoshi Atake Tooru Saito Kazuya
- 出版者
- American Institute of Physics
- 雑誌
- The journal of chemical physics (ISSN:00219606)
- 巻号頁・発行日
- vol.130, no.3, pp.034503, 2009-01
- 被引用文献数
- 24 7
The heat capacities of single crystals of organic ferroelectric complexes phenazine-chloranilic acid (Phz-H2ca) and phenazine-bromanilic acid (Phz-H2ba) were measured. At temperatures below those of the reported ferroelectric phase transitions,heat capacity anomalies due to successive phase transitions were found in both complexes. Excess entropies involved in the low-temperature successive phase transitions are much larger than those due to the ferroelectric phase transitions. The temperature dependence of the complex dielectric constants showed the existence of multiple dielectric relaxation modes in both complexes and their deuterated analogs (Phz-D2ca and Phz-D2ba). We discuss the possibility of concerted hopping of neighboring protons within a hydrogen-bonded chain while taking into account the one-dimensional nature of the chain.
1 0 0 0 OA Hard x-ray photoelectron spectroscopy study on valence band structure of semiconducting BaSi2
- 著者
- Baba Masakazu Ito Keita Du Weijie Sanai Tatsunori Okamoto Kazuaki Toko Kaoru Ueda Shigenori Imai Yoji Kimura Akio Suemasu Takashi
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.114, no.12, pp.123702, 2013-09
- 被引用文献数
- 15
The valence band structures of a 35-nm-thick BaSi2 epitaxial film on Si(111) have been explored at room temperature by hard x-ray photoelectron spectroscopy (HAXPES). The experimentally obtained photoelectron spectrum is well reproduced by first-principles calculations based on the pseudopotential method. The top of the valence band consists mainly of Si 3s and 3p states in BaSi2, suggesting that the effective mass of holes is small in BaSi2. This is favorable from the viewpoint of solar cell applications. The observed spectrum shifted slightly to the lower energy side due to n-type conductivity of BaSi2. The valence band top was observed at about 0.8 eV below the Fermi level in the HAXPES spectrum.
- 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
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
- Yamaoka Yuuki Taniguchi Yuki Yasuzuka Syuma Yamamura Yasuhisa Saito Kazuya
- 出版者
- American Institute of Physics
- 雑誌
- The journal of chemical physics (ISSN:00219606)
- 巻号頁・発行日
- vol.135, no.4, pp.044705, 2011-07
- 被引用文献数
- 30 12
Quasi-binary (QB) picture of thermotropics, which regards a neat thermotropic liquid crystal as a binary system consisting of (semi)rigid core and molten alkyl chain, was assessed experimentally for the most famous (and representative) thermotropic mesogenic series nCB. By adding n-heptane as solvent, the smectic A phase was induced in 7CB–n-heptane system. Small angle x-ray diffraction showed that the QB picture holds not only in the phase behavior but also in the structure. It is suggested that the melting of 8CB and 9CB to isotropic liquid via smectic and nematic liquid crystals can be understood as a thermotropic–lyotropic crossover.
- 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
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
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.
1 0 0 0 OA Coherent monochromatic phonons in highly purified semiconducting single-wall carbon nanotubes
- 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
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
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.
1 0 0 0 OA Two-dimensional magnetic interactions and magnetism of high-density charges in a polymer transistor
- 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
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
- Nozokido T. Ishino M. Kudo H. Bae J.
- 出版者
- American Institute of Physics
- 雑誌
- Review of scientific instruments (ISSN:00346748)
- 巻号頁・発行日
- vol.84, no.3, pp.036103, 2013-03
- 被引用文献数
- 7
Imaging of thermal radiation with a spatial resolution below the diffraction limit is demonstrated with a passive millimeter-wave microscope. This technique utilizes a sensitive radiometric receiver in combination with a scanning near-field microscope. Experiments were performed at 50 GHz (λ = 6 mm) with sample temperatures ranging from room temperature down to 160 K, and the performance was shown to be superior to that achieved with passive imaging systems in the infrared region. The images are affected by non-uniformities in the transmission of thermal radiation from the sample to the receiver via the near-field probe and the reflection of thermal radiation back to the receiver from the probe. The effects of these non-uniformities were successfully removed using a sample image acquired by active measurements using a vector network analyzer.
- 著者
- Benseman T. M. Koshelev A. E. Kwok W.-K. Welp U. Vlasko-Vlasov V. K. Kadowaki K. Minami H. Watanabe C.
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.113, no.13, pp.133902, 2013-04
- 被引用文献数
- 55
Stacks of intrinsic Josephson junctions (IJJs) made from high-temperature superconductors such as Bi2Sr2CaCu2O8+δ (Bi-2212) (BSCCO) are a promising source of coherent continuous-wave terahertz radiation. It is thought that at electrical bias conditions under which THz-emission occurs, hot spots may form due to resistive self-heating, and that these spots may be highly beneficial for the generation of high levels of THz power. Here, we perform an imaging study of the temperature distribution at the surface of BSCCO stacks utilizing the temperature-dependent 612 nm fluorescence line of Eu3+ in a europium chelate. The images directly reveal a highly non-uniform temperature distribution in which the temperature in the middle of the stack can exceed the superconducting transition temperature by tens of Kelvin under biasing conditions typical for THz-emission.
- 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
- Nakamura K. Baba M. Ajmal Khan M. Du W. Sasase M. Hara K. O. Usami N. Toko K. Suemasu T.
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.113, no.5, pp.053511, 2013-02
- 被引用文献数
- 21 11
A 180-nm-thick boron (B) layer was deposited on a 300-nm-thick a-axis-oriented BaSi2 epitaxial film grown by molecular beam epitaxy on Si(111) and was annealed at different temperatures in ultrahigh vacuum. The depth profiles of B were investigated using secondary ion mass spectrometry (SIMS) with O2+, and the diffusion coefficients of B were evaluated. The B profiles were reproduced well by taking both the lattice and the grain boundary (GB) diffusions into consideration. The cross-sectional transmission electron microscopy (TEM) image revealed that the GBs of the BaSi2 film were very sharp and normal to the sample surface. The plan-view TEM image exhibited that the grain size of the BaSi2 film was approximately 0.6 μm. The temperature dependence of lattice and GB diffusion coefficients was derived from the SIMS profiles, and their activation energies were found to be 4.6 eV and 4.4 eV, respectively.