著者

Ko Jae-Hyeon Kojima Seiji Bokov Alexei A. Ye Zuo-Guang

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.91, no.25, pp.252909, 2007-12

被引用文献数

36 25

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The dynamic polar nanoregions (PNRs) which form below the Burns temperature and determine the unique properties of relaxor ferroelectrics were predicted [Tinte et al., Phys. Rev. Lett. 97, 137601 (2006)] to be pinned to the quenched chemically ordered regions (CORs) usually observed in lead-containing relaxors. In Pb[(Mg1/3Nb2/3)0.45Ti0.55]O3 crystal where CORs are known to be absent, we have found the phenomena typically related to the relaxation of dynamic PNRs, namely, the significant Brillouin quasielastic scattering, the softening of the longitudinal acoustic mode, and the deviation from the Curie-Weiss law above the Curie point. This implies that PNRs may appear in crystals without CORs.

著者

Yamaguchi Ryo-taro Hirano-Iwata Ayumi Kimura Yasuo Niwano Michio Miyamoto Ko-ichiro Isoda Hiroko Miyazaki Hitoshi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.91, no.20, pp.203902, 2007-11

被引用文献数

13

---

We have developed a method for real-time monitoring of the cell responses to cytotoxicants using Fourier transform infrared spectroscopy with the multiple internal reflection (MIR-FTIR) geometry. To prevent cell damages induced by measurement environments, we have constructed specialized chambers, in which temperature was maintained at (37±0.5) °C and humidified air containing 5% CO2 was supplied. We monitored cell death induced by cytotoxic surfactant Tween20 using MIR-FTIR spectroscopy. It was found that cell death can be monitored by the absorption intensity of amide II band. This result suggests that our method has a potential to be applied for real-time cytotoxicity assay.

著者

Ootsuka Teruhisa Fudamoto Yasunori Osamura Masato Suemasu Takashi Makita Yunosuke Fukuzawa Yasuhiro Nakayama Yasuhiko

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.91, no.14, pp.142114, 2007-10

被引用文献数

23 25

---

We have clearly observed photoresponse properties in an Al/n-beta-FeSi2 structure using beta-FeSi2 single crystals grown by chemical vapor transport. A photocurrent is observed for photons with energies greater than 0.68 eV. It increases sharply with increasing photon energy and attains a maximum at approximately 0.95 eV (1.31 µm). The photocurrent originated from the photoexcited electrons in the Al and the band-to-band photoexcited carriers in the beta-FeSi2 located under the Al contact. The photoresponsivity increased upon high-temperature annealing, reaching 58 mA/W at 0.95 eV after annealing at 800 °C for 8 h.

著者

Fujiwara Seiji Bando Kazuki Masumoto Yasuaki Sasaki Fumio Kobayashi Shunsuke Haraichi Satoshi Hotta Shu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.91, no.2, pp.021104, 2007-07

被引用文献数

30 27

---

Laser oscillation of whispering gallery modes was observed in microring structures of semiconducting thiophene/phenylene co-oligomer (TPCO) crystals at room temperature. Microring structures were formed by dry etching from thin film crystals of TPCO. The thresholds for the laser oscillation of a microring and a thin film crystal are 200 and 1400 µJ/cm2 for picosecond excitation, respectively. Therefore, the threshold for the microring was reduced to 1/7 of that for the thin film crystal. The dramatic reduction of threshold clearly demonstrates the importance of microcavity in making efficient organic semiconductor lasers.

著者

Hattori Toshiaki Sakamoto Masaya

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.90, no.26, pp.261106, 2007-06-25

被引用文献数

16

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The authors have developed a method of real-time terahertz imaging in which image deformation due to nonuniformity of residual birefringence in the electro-optic (EO) sampling crystal is corrected. Real-time terahertz imaging using intense terahertz pulses and two-dimensional EO sampling can suffer from birefringence nonuniformity of the EO crystal since the birefringence is explicitly used for the linear detection of the terahertz field. In the proposed method, the distribution of the residual birefringence of the EO crystal is measured and used for image correction. Deformation-free images of the spatial profile of a focused terahertz pulse were obtained.

著者

Fukata N. Chen J. Sekiguchi T. Matsushita S. Oshima T. Uchida N. Murakami K. Tsurui T. Ito S.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.90, no.15, pp.153117, 2007-04

被引用文献数

40 32

---

Phosphorus (P) doping was performed during the synthesis of silicon nanowires (SiNWs) by laser ablation. At least three types of signals were observed by electron spin resonance (ESR) at 4.2 K. Phosphorus doping into substitutional sites of crystalline Si in SiNWs was demonstrated by the detection of an ESR signal with a g value of 1.998, which corresponds to conduction electrons in crystalline Si, and by an energy-dispersive x-ray spectroscopy spectrum of the P Kalpha line. The ESR results also revealed the presence of defects. These defects were partially passivated by hydrogen and oxygen atoms.

著者

Nakamura Yoshiaki Ichikawa Masakazu Watanabe Kentaro Hatsugai Yasuhiro

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.90, no.15, pp.153104, 2007-04

被引用文献数

40 33

---

A scanning tunneling microscopic study revealed quantum fluctuation of tunneling currents in individual Ge quantum dots (QDs) on SiO2/Si. This was due to the charging energy change in the QDs caused by single-electron transfer from or into the QDs. The observed electron discharging time of approximately milliseconds agreed with the propagation model of the electron wave packets from the QDs to the Si substrates by a tunneling effect rather than by passing through voids in the SiO2 smaller than electron de Broglie wavelength.

著者

Maczka Miroslaw Hanuza Jerzy Majchrowski Andrzej Kojima Seiji

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.90, no.12, pp.122903, 2007-03

被引用文献数

5

---

K2MgWO2(PO4)2 single crystal, related to famous optical nonlinear material KTiOPO4, was investigated by micro-Brillouin scattering with a focus on the central components of the relaxation modes. A critical slowing down has been clearly observed in the vicinity of T1=436 K while suppressed by the coupling with the order parameter. The temperature dependence of the relaxation time indicates that the former transition is the second order, while the latter is strongly first order. The obtained results show that disorder processes in the sublattice of potassium ions play a major role in the mechanism of these phase transitions.

著者

Kato K. Takata M. Moritomo Y. Nakamoto A. Kojima N.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.90, no.20, pp.201902, 2007

被引用文献数

25

---

A photoexcitation is one of the promising external fields to control the material phases. Here, the authors have demonstrated that the magnetic and structural properties of a spin-crossover complex, Fe(phen)2(NCS)2 (phen=1,10-phenanthroline), can be reversibly switched by the on-off action of the continuous photoexcitation at the same temperature. The structural data suggest that the density of the high-spin Fe2+ in the photoinduced phase is about 0.88. Suppressed atomic vibrations of the photoinduced phase exclude the conventional heating effect as the origin for the observed optical switching.

著者

Fukata N. Chen J. Sekiguchi T. Okada N. Murakami K. Tsurui T. Ito S.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.89, no.20, pp.203109, 2006-11

被引用文献数

54 38

---

Local vibrational modes of boron (B) in silicon nanowires (SiNWs) synthesized by laser ablation were observed at about 618 and 640 cm−1 by Raman scattering measurements. Boron doping was performed during the growth of SiNWs. Fano [Phys. Rev. 124, 1866 (1961)] broadening was also observed in the Si optical phonon peak. These results prove that B atoms were doped in the SiNWs. Hydrogen (H) passivation of B acceptors in the SiNWs was also investigated. A broad peak was observed at around 650–680 cm−1 after hydrogenation, demonstrating that B dopants were passivated by the formation of the well-known H–B passivation centers.

著者

Tsukada Shinya Ike Yuji Kano Jun Sekiya Tadashi Shimojo Yoshihito Wang Ruiping Kojima Seiji

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.89, no.21, pp.212903, 2006-11

被引用文献数

40 28

---

Brillouin and Raman scatterings of a 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3 single crystal have been measured to investigate broadband inelastic spectra. The two different central peaks related to fast and slow relaxation processes have been observed separately. These two processes are attributed to the thermally activated switching of polarization in polar nanoregions. By the analysis of modified superparaelectric model, the activation energies of fast and slow relaxation processes are determined to be 3.66×103 and 4.31×102 K, respectively. The fast process with the lower activation energy probably originated from 180° switching, whereas the slow one with the higher energy from non-180° switching.

著者

Asaka Koji Kato Ryoei Miyazawa Kun'ichi Kizuka Tokushi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.89, no.19, pp.191914, 2006-11

被引用文献数

8 10

---

The deformation of isolated multiwalled carbon capsules of a few nanometers in diameter was observed by in situ transmission electron microscopy with simultaneous force measurement by means of an optical cantilever method as used in atomic force microscopy. The mechanical properties of the carbon nanocapsules were investigated on an atomic scale. A carbon nanocapsule of 2.50±0.06 nm in diameter was selected and compressed upto a strain of 0.06 at a force of up to 4.5±0.5 nN using a nanometer-sized gold tip of a microcantilever. By subsequent retraction, we measured the force between the carbon nanocapsule and the gold tip, and assessed the adhesion.

著者

Makimura Tetsuya Uchida Satoshi Murakami Kouichi Niino Hiroyuki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.89, no.10, pp.101118, 2006-09

被引用文献数

21

---

In order to demonstrate silica nanomachining, the authors fabricated line-and-space contact masks with spaces of 53 and 70 nm on silica glass plates, followed by irradiation with laser plasma softx rays (LPSXs) with wavelengths around 10 nm. Trenches with the narrowest width of 54 nm and an aspect ratio of ~1 were fabricated by the LPSX irradiation through the contact masks. It was also clarified that silica glass can be machined by irradiation with LPSXs in the wavelength range of 6–30 nm in Ar gas which was used as an x-ray bandpass filter.

著者

Asaka Koji Kato Ryoei Miyazawa Kun'ichi Kizuka Tokushi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.89, no.7, pp.071912, 2006-08

被引用文献数

32

---

The authors demonstrated the mechanics of materials for crystalline whiskers composed of C60 molecules; compressive deformation of the whiskers was observed by in situ transmission electron microscopy with simultaneous force measurement by means of an optical cantilever method, as used in atomic force microscopy. In response to compression along the long axis, the whiskers bent first elastically, then buckled. A whisker with 160 nm diameter fractured brittlely at a strain of 0.08. According to Euler's formula, Young's modulus of the whisker was estimated to be 32–54 GPa, which is 160%–650% of that of C60 bulk crystals.

著者

Umeda T. Okonogi K. Ohyu K. Tsukada S. Hamada K. Fujieda S. Mochizuki Y.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.88, pp.253504, 2006-06

被引用文献数

25 18

---

The variable retention time phenomenon has recently been highlighted as an important issue in dynamic random access memory (DRAM) technology. Based on electrically detected magnetic resonance and simulation studies, we suggest that a single Si vacancy-oxygen complex defect is responsible for this phenomenon, when the defect is embedded in the near surface drain-gate boundary of a DRAM cell.

著者

Paul G. K. Nawa Y. Sato H. Sakurai T. Akimoto K.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.88, no.14, pp.141901, 2006-04

被引用文献数

88 41

---

Hole traps in p-type Cu2O were studied by means of deep level transient spectroscopy in the heterostructure of p-Cu2O/i-ZnO/n-ZnO. In addition to the trap level at about 0.45 eV from the valance band edge, which is already reported as being due to Cu vacancy, we found a new trap level at about 0.25 eV. The new trap is tentatively assigned as Cu-di-vacancy from the trap concentration dependence on oxygen flow rate and substrate temperature.

著者

Kita Eiji Tsukuhara Naoki Sato Hidenori Ota Keishin Yangaihara Hideto Tanimoto Hisanori Ikeda Naoshi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.88, pp.152501, 2006-04

被引用文献数

22 19

---

We prepared high-purity oxygen-free and single-phase Ni nanocrystals using the gas condensation and deposition method in order to examine the random anisotropy model (RAM). The grain size of an as-prepared sample was estimated to be 8–10 nm. Thermal annealing increased grain sizes (D) up to 22 nm. Clear D6 dependence of the coercive force on a grain size smaller than 13 nm was obtained for samples prepared on both plastic and KBr single-crystal substrates. For larger grain sizes, Hc decreased with D–1 and these results clearly conform to the RAM in single-element nanocrystal systems. A local anisotropy constant was estimated from the slope of the D6 relation and the peak of Hc at D=13 nm.

著者

Asaka Koji Kato Ryoei Maezono Yoshinari Yoshizaki Ryozo Miyazawa Kun'ichi Kizuka Tokushi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.88, no.5, pp.051914, 2006-02

被引用文献数

19

---

Filaments composed of multilayered carbon hollow capsules less than 10 nm in diameter have been synthesized from crystalline whiskers of fullerene C60 of submicrometer in diameter by preliminary heating at 1373 K and successive impression of current. The structural, electrical and optical properties of the filaments were studied by in situ transmission electron microscopy combined with the functions of scanning probe microscopy. We found that the filaments easily emit visible light at a maximum wavelength of 700-730 nm by the application of a few volts.

著者

Boero Mauro Oshiyama Atsushi Silvestrelli Pier Luigi Murakami Kouichi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.86, no.20, pp.201910, 2005-05

被引用文献数

17 18

---

Recent experiments have shown that pure Si structures in a matrix of SiO2 can be formed by electron excitation techniques, with appealing applications in nanotechnology. Our ab initio simulations provide an insight into the underlying mechanism, showing that electron excitations weaken Si–O bonds in SiO2, dislodge O atoms and allow Si dangling bonds to reconstruct in stable Si–Si structures below the melting temperature. Differences in diffusivity of O (fast) and Si (slow) are shown to play a decisive role in the process.

著者

Fukata N. Oshima T. Murakami K. Kizuka T. Tsurui T. Ito S.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.86, no.21, pp.213112, 2005-05

被引用文献数

79 50

---

A gradual downshift and asymmetric broadening of the Si optical phonon peak were observed by Raman scattering measurements of continuously thermally oxidized silicon nanowires (SiNWs) synthesized by laser ablation. This downshift and broadening can be interpreted by the phonon confinement effect. Further thermal oxidation produced a reverse change; namely, an upshift of the optical phonon peak. This is considered to be due to compressive stress since this stress was relieved by removing the oxide layers formed around the SiNW cores, resulting in a downshift of the optical phonon peak.