研究者詳細 - 紀和　利彦

A proton pumping gate field-effect transistor for a hydrogen gas sensor

Keiji Tsukada, Tomiharu Yamaguchi, Toshihiko Kiwa

IEEE Sensors Journal 7 ( 9 ) 1268 - 1269 2007年9月

記述言語：英語出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

A proton pumping field-effect transistor (FET), consisting of a triple layer gate structure of a Pd/proton conducting polymer/Pt, has been developed. The hydrogen sensitivity was controlled by the bias change between Pt and Pd. Furthermore, two kinds of methods for the readout of DC and AC modulation can be achieved. According to the decrement of the bias frequency, the modulated output was increased. This characteristic realizes a gas sensor with a self-check function. © 2007 IEEE.

DOI： 10.1109/JSEN.2007.901268

Fourier-transformed eddy current technique to visualize cross-sections of conductive materials

Toshihiko Kiwa, Tomoaki Kawata, Hironobu Yamada, Keiji Tsukada

NDT and E International 40 ( 5 ) 363 - 367 2007年7月

記述言語：英語出版者・発行元：ELSEVIER SCI LTD

A pulsed eddy current NDE system is useful for detecting deep flaws in conductive materials. We have developed a pulsed eddy current NDE system using a magneto-resistive sensor. The induction coil generates a pulsed magnetic field which has a frequency component between 0 and 3 kHz, and a maximum amplitude of about 4 μ T. Aluminum plates with flaws at depths of 1 and 2 mm were measured, and the intrinsic frequency responses of the plates were obtained using a proposed Fourier transformation method. Cross-sectional images of the samples could then be directly constructed from the intrinsic responses. We also demonstrated estimation of quantitative values for the depths of flaws. The estimated depth was well defined for a sample with a flaw at a depth of 2 mm. The estimated value was slightly different for a sample with a flaw at a depth of 1 mm due to lack of frequency components above 3 kHz. These results indicate that the proposed system is a very promising tool for NDE tomography. © 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ndteint.2007.01.006

Detection of photomixing signals with a YBCO Josephson junction coupled to a coplanar waveguide

Iwao Kawayama, Ryuhei Kinjo, Toshihiko Kiwa, Hironaru Murakami, Masayoshi Tonouchi

IEEE Transactions on Applied Superconductivity 17 ( 2 ) 321 - 323 2007年6月

記述言語：英語出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

We have fabricated a generation and detection system of photomixing signals using a photomixing technique and a Josephson junction detector. Up to now, an electromagnetic wave generated by a heterodyne mixing of two lasers was emitted from an antenna, and irradiated to a Josephson junction. In this study, we have developed the system, and the photomixing signal was introduced into a coaxial cable and a coplanar wave guide coupled to a Josephson junction. This structure is more suitable for device application since it can easily be integrated into electronic devices. With this system we can clearly observed photomixing signals from 16 GHz to 95 GHz using a uni-traveling-carrier photodiode as a photomlxer as well as signals in the range of 14 GHz to 50 GHz using an InGaAs PIN photodiode. © 2007 IEEE.

DOI： 10.1109/TASC.2007.898106

Magnetic measurement of moisture content of grain

Keiji Tsukada, Toshihiko Kiwa

IEEE Transactions on Magnetics 43 ( 6 ) 2683 - 2685 2007年6月

記述言語：英語出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

We developed a technique to magnetically measure the moisture content of grain. The measurement method developed consists of an exposure magnetic coil, and a magnetic resistance sensor. When the grain is exposed to alternating magnetic fields of low frequency, a secondary magnetic field generated from the grain is observed. Two kinds of grain with different water absorption abilities (nonglutinous rice and glutinous rice) were measured. The secondary magnetic field strength of the grain increased incrementally with the moisture content. The experimental result indicated the applicability of the developed magnetic measurement method for nondestructive moisture measurement. © 2007 IEEE.

DOI： 10.1109/TMAG.2007.892853

Oxygen interference mechanism of platinum-FET hydrogen gas sensor

T. Yamaguchi, T. Kiwa, K. Tsukada, K. Yokosawa

Sensors and Actuators, A: Physical 136 ( 1 ) 244 - 248 2007年5月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE SA

This paper reports the effect of oxygen in air on a Pt-FET hydrogen sensor. The output voltage change of the Pt-FET had good linearity to the logarithm of hydrogen concentration in nitrogen. The slope of the linear curve is -26.4 mV/decade, which is close to the calculated value of the Nernstian slope. This indicates the response mechanism of the Pt-FET sensor is based on the catalytic reaction on the Pt surface. However, the output voltage change of the Pt-FET was not proportional to the logarithm of hydrogen concentration in air due to adsorbed oxygen on the Pt surface. This indicates the water formation for the reaction of hydrogen and oxygen on the Pt surface is the main hydrogen response mechanism in air. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2006.11.026