Faculty Profiles - KISODA Kenji

Published Papers - KISODA Kenji

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Lattice dynamics and Raman spectra of strained hexagonal GaN/AlN and GaN/AlGaN superlattices

V. Yu Davydov, A. N. Smirnov, M. B. Smirnov, S. V. Karpov, I. N. Goncharuk, R. N. Kyutt, M. V. Baidakova, A. V. Sakharov, E. E. Zavarin, W. V. Lundin, H. Harima, K. Kisoda

Physica Status Solidi C: Conferences ( 7 ) 2035 - 2038 2003 [Refereed]

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Lattice dynamics and Raman spectra of strained hexagonal GaN/AlN and GaN/AlGaN superlattices

VY Davydov, AN Smirnov, MB Smirnov, SV Karpov, IN Goncharuk, RN Kyutt, MV Baidakova, AV Sakharov, EE Zavarin, WV Lundin, H Harima, K Kisoda

5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS ( WILEY-VCH, INC ) 0 ( 7 ) 2035 - 2038 2003 [Refereed]

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Intrinsic localized vibrational modes in a highly nonlinear halogen-bridged metal

K Kisoda, N Kimura, H Harima, K Takenouchi, M Nakajima

JOURNAL OF LUMINESCENCE ( ELSEVIER SCIENCE BV ) 94 743 - 746 2001.12

Intrinsic localized vibrational modes in a halogen-bridged Pt complex were studied by Raman spectroscopy. We compared the peak frequency of the overtone of Pt-Cl stretch vibration between that excited by an Ar+ and that by a near infrared (NIR) lasers. The decrease in the overtone peak frequency of the NIR excitation were larger than that of the visible excitation. We interpreted that the charge transfer led to weaken the bond strength and that the anharmonicity of the system became weak. (C) 2001 Elsevier Science B.V. All rights reserved.

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Peculiar noise properties of phonons generated by femtosecond laser pulses in antimony

OV Misochko, K Kisoda, K Sakai, S Nakashima

APPLIED PHYSICS LETTERS ( AMER INST PHYSICS ) 76 ( 8 ) 961 - 963 2000.02

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Dynamics of low-frequency phonons in the YBa2Cu3O7-x superconductor studied by time- and frequency-domain spectroscopies

OV Misochko, K Kisoda, K Sakai, S Nakashima

PHYSICAL REVIEW B ( AMER PHYSICAL SOC ) 61 ( 6 ) 4305 - 4313 2000.02 [Refereed]

We have investigated the temperature dependence of the optical reflectivity at femtosecond scale in YBa2Cu3O7-x superconductors. In both normal and superconducting states, we detect the oscillations associated with two A(1g) metal-ion modes and compare the phonon dynamics to those obtained by frequency-domain (Raman) spectroscopy. Apart from the considerable increase of amplitude for low-frequency mode in the superconducting state, we observe that its initial phase in the time domain is approximately pi/4 shifted by the superconductivity, whereas for the high-frequency mode the initial phase shift is almost two times larger. Even though similar lattice anomalies are observed in both time and frequency domains, the systematic analysis shows that the coherent lattice dynamics is different from the ordinary (thermal state) dynamics probed by frequency-domain spectroscopy.

Dynamics of low-frequency phonons in the YBa2 Cu3O7-x Superconductor studied by time-and frequency-domain spectroscopies

O. V. Misochko, K. Kisoda, K. Sakai, S. Nakashima

Physical Review B 61 ( 6 ) 4305 - 4313 2000

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Mesoscopic scanning tunneling and atomic force microscopy study of the misfit-layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2

SA Contera, T Yoshinobu, H Iwasaki, K Kisoda

SURFACE SCIENCE ( ELSEVIER SCIENCE BV ) 441 ( 2-3 ) 384 - 390 1999.11

The surface of the misfit-layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2 is studied by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM), in air and nitrogen, in the range of 0.5 to 10 mu m(2). The cleaved surface of (LaSe)(x)NbSe2 presents flat non-stepped surfaces which crack and react. Inner layers do not appear to crack. The dynamic process taking place in the superficial layers produces pieces which arrange in a self-similar way and eventually gives rise to discrete islands which self-organize periodically in one direction. On the other hand, the cleaved surface of (PbSe)(x)NbSe2 is stepped and shows no reactivity. The influence of the cleavage, the strain, the strength of the interlayer and intralayer bonding, and the misfit of the compounds are discussed as reasons for the mesoscopic behaviour of these materials, (C) 1999 Elsevier Science B.V. All rights reserved.

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Mixing of low-frequency Raman-active phonons studied by femtosecond pump-probe spectroscopy

OV Misochko, K Kisoda, H Harima, K Mizoguchi, K Sakai, S Nakashima

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS ( ELSEVIER SCIENCE BV ) 320 ( 3-4 ) 213 - 217 1999.07

We report an optical study of the superconducting transition in the YBa(2)Cu(3)O(7-x) films on MgO substrate carried out by femtosecond pump-probe spectroscopy. In both the normal and the superconducting state, we have observed the transient time-resolved reflectivity caused by the oscillations associated with two A,, metal-ion modes. Temporal interference between the modes is modified below the phase transition, which also appeared in an altered relative intensity of the modes in the Fourier transformed spectra. (C) 1999 Elsevier Science B.V. All rights reserved.

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Pump power dependence of coherent phonons in eta-Mo4O11

K Kisoda, M Hase, H Harima, S Nakashima, K Sakai, M Tani, H Negishi, M Inoue

PHYSICA B-CONDENSED MATTER ( ELSEVIER SCIENCE BV ) 263 51 - 53 1999.03

We studied the pump power dependence of the coherent phonon amplitude in the CDW and the normal states of eta-Mo4O11, which undergoes two CDW phase transitions at T-c1 = 105 K and T-c2 = 35 K. Femtosecond time-resolved pump-probe measurements were conducted at room temperature, 80 K (< T-c1), and 20 K (< T-c2). Unlike Raman spectra, the coherent phonon amplitudes showed a strong pump power dependence below T-c1 and T-c2. We found coherent phonons of which amplitudes were not proportional to the pump power. (C) 1999 Elsevier Science B.V. All rights reserved.

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Phonons in V2O3 above and below the Mott transition: a comparison of time- and frequency-domain spectroscopy results

OV Misochko, M Tani, K Sakai, K Kisoda, S Nakashima, VN Andreev, FA Chudnovsky

PHYSICA B ( ELSEVIER SCIENCE BV ) 263 57 - 59 1999.03

We report an optical study of the Mott transition in V2O3 carried out by time- and frequency-domain spectroscopies. We have observed time-resolved spectra through the Mott transition with oscillations in reflectivity associated with the fully symmetric phonon modes. Raman spectrum also shows an abrupt change of both the phonon and electronic excitations through the phase transition. We notice that although the phonon spectra obtained by the time- and frequency-domain spectroscopies are essentially similar, there are distinct differences in the phonon lineshape. (C) 1999 Elsevier Science B.V. All rights reserved.

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Scanning tunneling microscopy study of the misfit layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2

SA Contera, T Yoshinobu, H Iwasaki, K Kisoda

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS ( JAPAN J APPLIED PHYSICS ) 37 ( 11 ) 6157 - 6160 1998.11

Atomic images of the misfit layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2 were obtained with a scanning tunneling microscope (STM) operating in constant height mode in air. It was possible to record pictures of only the NbSe2 layers of both compounds, the LaSe and PbSe layers could not be observed. Formation of stage-2 portions embedded in the stage-1 crystal and instability of the LaSe and PbSe layers under the scanning conditions are discussed as possible causes. Comparing with the NbSe2 crystal, the lattice of the NbSe2 layers of the misfit layer compounds appear deformed. Nonperiodic Moire-like structures have been observed in the (LaSe)(x)NbSe2 surface. We consider that this feature is caused by the STM tip pushing down the surface where it is softer. The nonperiodicity of the patterns might be due to the strain conditions of the crystal growth that would give rise to dislocations and defects.

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Optical study of the Mott transition in V2O3: Comparison of time- and frequency-domain results

OV Misochko, M Tani, K Sakai, K Kisoda, S Nakashima, VN Andreev, FA Chudnovsky

PHYSICAL REVIEW B ( AMER PHYSICAL SOC ) 58 ( 19 ) 12789 - 12794 1998.11 [Refereed]

We report the results of an optical study of the Mott transition in V2O3 carried out by time- and frequency domain spectroscopies. We have observed time-resolved spectra through the Mott transition with oscillations in reflectivity associated with the fully symmetric modes. As a consequence of the phase transition, the Raman spectrum also shows an abrupt change of both the phonon and electronic excitations. Most notable are (i) disappearance of the electronic continuum, which is very strong and broad in the metallic state, and (ii) altered coupling of a fully symmetric phonon to the electronic subsystem, which is shown to be temperature dependent even above the transition. We notice that although the spectra obtained by the time- and frequency-domain spectroscopies are similar, there are distinct differences in phonon line shape. [S0163-1829(98)04743-2].

STM study of the reactivity of niobium diselenide in air and N(2)

SA Contera, T Yoshinobu, H Iwasaki, K Kisoda, S Nakashima

APPLIED SURFACE SCIENCE ( ELSEVIER SCIENCE BV ) 130 623 - 628 1998.06

STM has been used to investigate the variety of processes taking place in the surface of NbSe(2) in air and N(2). Induced surface layer by layer etching and formation and evolution of surface reaction sites both in air and N(2), are discussed. Residues removed and transported by the tip were found in N(2) but they seemed to get dissolved in air. Rests of chemicals (and/or surface defects) have been observed to be left in the edges of pre-existing terrace steps in N(2), providing a preferential place for the formation of new reaction sites when air was re-introduced. In places where apparently no defects were present, the tip induced etching process was not possible, but focusing in a pre-existing small depression, the etching proceeded fast not only in that layer but also in the layers beneath. We propose that the processes taking place at the surface of NbSe(2) are due to mechanical and chemical interactions that unsaturated bonds which are present in surface defects and step edges have with the environment and the tip. (C) 1998 Elsevier Science B.V. All rights reserved.

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Coherent phonons from the CDW state in η -Mo4O11

K. Kisoda, M. Hase, H. Harima, S. Nakashima, M. Tani, K. Sakai, H. Negishi, M. Inoue

Physical Review B 58 ( 12 ) R7484 - R7487 1998

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Optical study of the Mott transition in V2O3 : Comparison of time-and frequency-domain results

O. V. Misochko, M. Tani, K. Sakai, K. Kisoda, S. Nakashima, V. N. Andreev, F. A. Chudnovsky

Physical Review B 58 ( 19 ) 12789 - 12794 1998

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Studies on low temperature structure of infinite-layered superconductor Sr1-xLaxCuO2 (0 <= x <= 0.12)

G Er, S Kikkawa, M Takahashi, F Kanamaru, M Hangyo, K Kisoda, S Nakashima

PHYSICA C ( ELSEVIER SCIENCE BV ) 290 ( 1-2 ) 1 - 8 1997.10

Low temperature structure was investigated on infinite-layered Sr1-xLaxCuO2 (0 less than or equal to x less than or equal to 0.12, La-IL) superconductor by X-ray absorption fine structure (XAFS), X-ray diffraction (XRD) and Raman spectroscopy. XAFS showed that Cu-O bond distance slightly expanded with lowering temperature down to 20 K, and the expansion was remarkable below T-c(onset) = 43 K. Tetragonal lattice parameters shrank with lowering temperature but the shrinkage of the a-parameter seemed to be almost saturated below T-c(onset). Resonance Raman peaks were observed at 151 cm(-1) and 304 cm(-1) in the La-doped samples, although the ideal IL structure should be Raman inactive. The peak intensities increased with lowering temperature. The variation may be related to the change observed with both XAFS and XRD in local structure with temperature. It is assumed that the CuO2 plane may buckle with shifting oxygen ion positions above and below the CuO2 plane, as reported in another electron-doped superconductor Nd2-xCexCuO4 (T'-214). (C) 1997 Elsevier Science B.V.

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Optical reflection and Raman studies on mixed crystals of misfit layer compounds

K Kisoda, M Hangyo, J Kuroda, H Harima, S Nakashima

SOLID STATE COMMUNICATIONS ( PERGAMON-ELSEVIER SCIENCE LTD ) 103 ( 11 ) 597 - 602 1997.09

We have performed optical reflectivity measurements on the mixed crystals of misfit layer compounds (MxLa1-xS)NbS2 (M: metal = Sn, Pb; 0 less than or equal to x less than or equal to 1) to estimate the carrier density in conducting NbS2 layers. The carrier density monotonically increases with the metal content x. The variation of the carrier density with x can be explained in terms of the charge transfer from MxLa1-xS to NbS2 layers. The influence of the charge transfer on the vibrational properties in the mixed crystals is studied by Raman scattering measurements. The peak frequencies of the A modes confined to the NbS2 layer shift to the higher energy side with decreasing x. The frequency shifts of the phonon modes suggest that the inter-and intralayer interactions increase with increasing the degree of the charge transfer. (C) 1997 Elsevier Science Ltd.

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On the Raman shift in misfit layer compounds of metal-dichalcogenides (MX)(TX2) - An effect of the charge transfer on the intralayer noncentral forces

K Shirai, K Kisoda, M Hangyo, S Nakashima

SOLID STATE COMMUNICATIONS ( PERGAMON-ELSEVIER SCIENCE LTD ) 103 ( 3 ) 131 - 135 1997.07

In the misfit layer compounds of metal-dichalcogenides (MX)(TX2), there are two intense Raman bands, which have been ascribed as their origins to the in-plane and the out-of-plane vibrations in the host layer compounds. It is commonly observed that the frequency of the in-plane mode is appreciably increased, while that of the out-of-plane mode is almost unchanged, in the misfit layer compounds. The mechanism is investigated by means of the classical lattice dynamics. It is found that competition between increasing central forces and decreasing noncentral forces in the host layer is the cause of this change. In the misfit layer compounds, electrons are donated to the host layer, further filling the conduction band. Filling that band makes the distribution of the valence electrons more spherical, which eliminates the angle dependence on the adiabatic potential. (C) 1997 Elsevier Science Ltd.

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Raman scattering of disordered SiC

S Nakashima, K Kisoda, H Niizuma, H Harima

PHYSICA B-CONDENSED MATTER ( ELSEVIER SCIENCE BV ) 219-20 371 - 373 1996.04

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Charge transfer and phonons in misfit layer compounds (RS)(x)NbS2 (R equals rare earth; x approximate to 1.2)

K Kisoda, M Hangyo, S Nakashima, T Terashima, N Kojima

PHYSICA B-CONDENSED MATTER ( ELSEVIER SCIENCE BV ) 219-20 565 - 567 1996.04

Misfit layer compounds (RS)(x)NbS2 (R = rare earth; x approximate to 1.2) are made of two types of layers: RS and NbS2. Polarized Raman spectra have been measured on (RS)(x)NbS2 (R = La, Ce, Pr, Nd, Sm, Dy, Yb) in order to study the interlayer interaction between the RS and the NbS2 layers and the effect of the charge transfer from the RS layer to the NbS2 layer, The behavior of the intralayer E mode of the NbS2 layer in (RS)(x)NbS2 is sensitive to the charge transfer and shifts considerably to higher frequency compared with that of the pristine compound 2H-NbS2. Two Raman bands whose peak frequencies depend on the mass of the R atoms appear below 200 cm(-1). These bands are attributed to the mode relevant to the RS layer.

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