Faculty Profiles - KIWA Toshihiko

Papers - KIWA Toshihiko

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Pulse current response of high-T <inf>c</inf> superconducting vortex flow transistors Reviewed

Y. Doda, T. Kiwa, I. Kawayama, H. Murakamia, M. Tonouchi

Chinese Journal of Physics 42 ( 4 II ) 458 - 462 2004.8

Language：English Publishing type：Research paper (international conference proceedings) Publisher：PHYSICAL SOC REPUBLIC CHINA

The properties of superconducting vortex flow transistor (SVFT), which consist of a vortex flow channel and a control line for applying a magnetic field, are diagnosed by using a current pulses train method. The time-domain waveforms of the vortex flow voltage along the channel were measure using the current pulses train with the pulse width of 5 ms as input signals. The fast response of the flow voltage suggests that the heating effect is negligible and the effect of the magnetic field generated by the control line was dominant in our measurement. The vortex flow speed was estimated from the ratio of the flux flow voltage to the control current, and was found to be 8.6×10 4 m/s. We also estimated the pinning energy E p from the vortex flow speed, and found that the value of E p is around 8.6 meV for our device, which can be easily excited by a conventional Ti:sapphire femtosecond laser.

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Photomixer with superconductor detector for sub-THz generator Reviewed

Toshihiko Kiwa, Masayoshi Tonouchi

Proceedings of SPIE - The International Society for Optical Engineering 5354 121 - 128 2004

Language：English Publishing type：Research paper (international conference proceedings) Publisher：SPIE-INT SOC OPTICAL ENGINEERING

A new type of optical-microwave conversion system has been proposed as high-stabilized oscillators and optical interfaces for superconducing circuits. The photomixer with heterodyne mixing of two lasers was applied to generate the electromagnetic waves and high-TC grain boundary Josephson junction detector was used to monitor the frequency of electromagnetic waves in real time. The current-voltage properties of Josephson junction detector were examined and the system operation up to 50 GHz was demonstrated. We also described in detail the two types of optical-microwave conversion system.

DOI： 10.1117/12.528892

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Non-contact measurement of MOSFET with zero bias voltage using the Laser-THz emission microscope Reviewed

Masatsugu Yamashita, Toshihiko Kiwa, Masayoshi Tonouchi, Kiyoshi Nikawa, Chiko Otani, Kodo Kawase

Conference Digest of the 2004 Joint 29th International Conference on Infrared and Millimeter Waves and 12th International Conference on Terahertz Electronics 515 - 516 2004

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

For inspecting electrical failures in large-scale integration (LSI) circuits, we developed the laser-THz emission microscope (LTEM), which records the map of THz emission amplitude in a sample upon excitation with fs laser pulses. We successfully observed the THz emission image of MOSFETs embedded in a test element group under zero bias voltage. This result suggests that the LTEM can be used not only for the defect localization in LSI failure analysis but also as in-line inspection and monitoring. © 2004 IEEE.

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Evaluation of spatial resolution in Laser-Terahertz emission microscope for inspecting electric faults in integrated circuits Reviewed

Masatsugu Yamashita, Toshihiko Kiwa, Masayoshi Tonouchi, Kodo Kawase

Proceedings of SPIE - The International Society for Optical Engineering 5354 104 - 111 2004

Language：English Publishing type：Research paper (international conference proceedings) Publisher：SPIE-INT SOC OPTICAL ENGINEERING

We have proposed and demonstrated a nondestructive and non-contact inspection method for electrical faults using laser-Terahertz (THz) emission microscopy (LTEM). By measuring the position dependence of the amplitude of the THz emission from integrated circuits (IC) excited with femtosecond (fs) laser pulses, it is possible to investigate the electrical faults in IC. By improving the spatial resolution of the system, we successfully observed the THz emission image of a microprocessor on standby mode. The LTEM system has a spatial resolution about 3μm and it can localize electrically defective sites in the chip to within a ten square microns.

DOI： 10.1117/12.528833

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Magnetic flux letters visualized by a laser-terahertz emission microscope Reviewed

Masayoshi Tonouchi, Toshihiko Kiwa, Takashi Fukui, Hironaru Murakami

Proceedings of SPIE - The International Society for Optical Engineering 5354 112 - 120 2004

Language：English Publishing type：Research paper (international conference proceedings) Publisher：SPIE-INT SOC OPTICAL ENGINEERING

Magnetic flux letters are visualized by a laser terahertz emission microscope (LTEM). LTEM excites terahertz (THz) radiation from electronics materials with a femtosecond laser and maps the amplitude of the THz waves while scanning laser beam on the sample. Magnetic flux letters written in high-Tc superconductors are successfully imaged without destroying them.

DOI： 10.1117/12.529026

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Laser terahertz emission microscope for inspecting electrical failures in integrated circuits Reviewed

Masatsugu Yamashita, Toshihiko Kiwa, Masayoshi Tonouchi, Kiyoshi Nikawa, Chiko Otani, Kodo Kawase

IMFEDK 2004 - International Meeting for Future of Electron Devices, Kansai 34 ( 9 ) 29 - 30 2004

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

© 2015 IEEE. The inspection and fault analysis of semiconductor devices has become a critical issue with increasing demands for quality and reliability in circuits as stated in L. A. Krauss et al. (2001), K. Nikawa (2002) and K. Nikawa et al. (2003). Recently, we have developed a laser-terahertz (THz) emission microscope (LTEM) that can be applied for the noncontact and nondestructive inspection of the electrical faults in circuits presented in K. Nikawa et al. (2003). The LTEM can image the amplitude profile of the THz wave emitted by scanning the sample with femtosecond (fs) laser pulses. The amplitude of the THz emission generated by the transient photocurrent is proportional to the local electric field at the laser-irradiated area according to T. Kowa et al. (2003). Therefore, the LTEM image of the semiconductor device while it operates reflects the electric field distribution in the chip. By comparing the LTEM image of a damaged chip with that of a normal one, we can localize the electrical faults. In this work, we report experimental results on a biased 8-bit microprocessor, as well as unbiased MOSFETs embedded in a test element group (TEG).

DOI： 10.1109/IMFEDK.2004.1566392

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Optical-microwave converter: Superconductor/photomixer hybrid system Reviewed

Toshihiko Kiwa, Masayoshi Tonouchi

IEEE MTT-S International Microwave Symposium Digest 2 1363 - 1366 2003

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

A new type of optical-microwave converter utilizing a photomixer and a high-Tc Josephson junction detector has been developed. The frequency difference of two laser beams has been observed in the characteristic of the high-Tc Josephson junction detector. The measured response of the detector for the microwave generated by photomixing two lasers suggests that the system can work as a highly sensitive wavelength meter with accuracy of ±3.5 pm. The system operation up to 20 GHz was also demonstrated by changing the wavelength of two laser beams.

DOI： 10.1109/MWSYM.2003.1212624

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A new wavemeter for C-band using Josephson junction

T. Kiwa, M. Tonouchi

OSA Trends in Optics and Photonics Series 88 1603 - 1604 2003

Terahertz radiation from amorphous GaAs thin film photoconductive switches Reviewed

T. Kiwa, I. Kawashima, M. Morimoto, H. Saijyo, S. Nashima, M. Yamashita, M. Tonouchi, M. Hangyo

CLEO/Pacific Rim 1999 - Pacific Rim Conference on Lasers and Electro-Optics 2 447 - 448 1999

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

© 1999 IEEE. Low-temperature grown GaAs (LT-GaAs) has been studied as a potential material for microwave-photonic devices such as a terahertz (THz) radiation emitter. Since the preparation of the LT-GaAs generally requires a post annealing process at around 600 °C, these has been limited to be a small number of the applications combined with other materials. In the present work, we study the photoresponse of amorphous (α-) GaAs prepared at between room temperature and 250 °C by femtosecond time-domain reflection pump-probe measurements and photo-induced THz emission measurements.

DOI： 10.1109/CLEOPR.1999.811513

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