Satoshi Shindo
Tohoku University
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Publication
Featured researches published by Satoshi Shindo.
Journal of Physics D | 2014
Yuta Saito; Satoshi Shindo; Yuji Sutou; Junichi Koike
Unusual chronological electrical resistance change behavior was investigated for amorphous GeCu2Te3 phase change material. More than a 1 order decrease of electrical resistance was observed in the air even at room temperature. The resistance of the amorphous film gradually increased with increasing temperature and then showed a drop upon crystallization. Such unusual behavior was attributed to the oxidation of the amorphous GeCu2Te3 film. From the compositional depth profile measurement, the GeCu2Te3 film without any capping layer was oxidized in air at room temperature and the formed oxide was mainly composed of germanium oxide. Consequently, a highly-conductive Cu-rich layer was formed in the vicinity of the surface of the film, which reduced the total resistance of the film. The present results could provide insight into the chronological change of electrical resistance in amorphous chalcogenide materials, indicating that not only relaxation of the amorphous, but also a large atomic diffusion contributes to the chronological resistance change.
ACS Applied Materials & Interfaces | 2018
Shogo Hatayama; Yuji Sutou; Satoshi Shindo; Yuta Saito; Yun-Heub Song; Daisuke Ando; Junichi Koike
Phase-change random access memory (PCRAM) has attracted much attention for next-generation nonvolatile memory that can replace flash memory and can be used for storage-class memory. Generally, PCRAM relies on the change in the electrical resistance of a phase-change material between high-resistance amorphous (reset) and low-resistance crystalline (set) states. Herein, we present an inverse resistance change PCRAM with Cr2Ge2Te6 (CrGT) that shows a high-resistance crystalline reset state and a low-resistance amorphous set state. The inverse resistance change was found to be due to a drastic decrease in the carrier density upon crystallization, which causes a large increase in contact resistivity between CrGT and the electrode. The CrGT memory cell was demonstrated to show fast reversible resistance switching with a much lower operating energy for amorphization than a Ge2Sb2Te5 memory cell. This low operating energy in CrGT should be due to a small programmed amorphous volume, which can be realized by a high-resistance crystalline matrix and a dominant contact resistance. Simultaneously, CrGT can break the trade-off relationship between the crystallization temperature and operating speed.
Zeitschrift für Physikalische Chemie | 2016
Kenji Kamimura; Koji Kimura; Shinya Hosokawa; Naohisa Happo; Hiroyuki Ikemoto; Yuji Sutou; Satoshi Shindo; Yuta Saito; Junichi Koike
Abstract The structure of crystal GeCu2Te3 was investigated by X-ray absorption fine structure (XAFS) measurement. We found that the Ge–Te interatomic distances obtained from XAFS are larger than those obtained from X-ray diffraction, and the Cu–Te distances are smaller. The averaged Ge–Te and Cu–Te distances obtained from XAFS are almost equal to the corresponding interatomic distances in amorphous GeCu2Te3. Therefore both crystal and amorphous GeCu2Te3 seem to be built up of the same local configurations of GeTe4 and CuTe4 tetrahedrons. This would be the reason why the phase change in GeCu2Te3 occurs very fast.
Optics Express | 2017
Ryota Akimoto; Hiroaki Handa; Satoshi Shindo; Yuji Sutou; Masashi Kuwahara; Makoto Naruse; Toshiharu Saiki
The functionality of a pulse timing discriminator, which is commonly required in optical communication systems and artificial neuromorphic engineering, was implemented into chalcogenide phase-change materials. GeSbTe (GST) and GeCuTe (GCT), which exhibit opposite refractive index behavior in their respective crystalline and amorphous phases, were employed. A GST/GCT double layer enabled the order of arrival of two counter-propagating femtosecond pulses to be encoded as a difference in the degree of amorphization of the GCT layer, i.e., either a brighter or darker contrast of the amorphized area with respect to the crystalline background. Nonthermal ultrafast amorphization contributed to a picosecond time resolution in the discrimination of the pulse arrival order.
Applied Physics Letters | 2018
Y. Shuang; Yuji Sutou; Shogo Hatayama; Satoshi Shindo; Yun-Heub Song; Daisuke Ando; Junichi Koike
Phase-change random access memory (PCRAM) is enabled by a large resistance contrast between amorphous and crystalline phases upon reversible switching between the two states. Thus, great efforts have been devoted to identifying potential phase-change materials (PCMs) with large electrical contrast to realize a more accurate reading operation. In contrast, although the truly dominant resistance in a scaled PCRAM cell is contact resistance, less attention has been paid toward the investigation of the contact property between PCMs and electrode metals. This study aims to propose a non-bulk-resistance-dominant PCRAM whose resistance is modulated only by contact. The contact-resistance-dominated PCM exploited here is N-doped Cr2Ge2Te6 (NCrGT), which exhibits almost no electrical resistivity difference between the two phases but exhibits a typical switching behavior involving a three-order-of-magnitude SET/RESET resistance ratio owing to its large contact resistance contrast. The conduction mechanism was discussed on the basis of current–voltage characteristics of the interface between the NCrGT and the W electrode.Phase-change random access memory (PCRAM) is enabled by a large resistance contrast between amorphous and crystalline phases upon reversible switching between the two states. Thus, great efforts have been devoted to identifying potential phase-change materials (PCMs) with large electrical contrast to realize a more accurate reading operation. In contrast, although the truly dominant resistance in a scaled PCRAM cell is contact resistance, less attention has been paid toward the investigation of the contact property between PCMs and electrode metals. This study aims to propose a non-bulk-resistance-dominant PCRAM whose resistance is modulated only by contact. The contact-resistance-dominated PCM exploited here is N-doped Cr2Ge2Te6 (NCrGT), which exhibits almost no electrical resistivity difference between the two phases but exhibits a typical switching behavior involving a three-order-of-magnitude SET/RESET resistance ratio owing to its large contact resistance contrast. The conduction mechanism was discus...
Applied Physics Letters | 2017
Yukiko Ogawa; Satoshi Shindo; Yuji Sutou; Junichi Koike
We investigated the temperature dependence of electrical resistance of a reactively sputtered Mo-oxide film with a composition near MoO3 and found that the sputtered Mo-oxide film shows a large electrical resistance drop of much more than 104-fold at over 350 °C. Such a large drop in electrical resistance was found to be caused by a phase transition from an amorphous state to a crystalline state. It was confirmed that a W/Mo-oxide/W device shows a typical resistive switching effect of a phase change random access memory material and exhibits reversible resistive switching by the application of unidirectional set and reset voltage. The resistance contrast of the device had a large value of about 105–106. Furthermore, the Mo-oxide film showed much better thermal stability in the amorphous state than conventional phase change materials. These results indicate that the Mo-oxide film is a promising oxide-base phase change material for phase change random access memory.
Materials Science in Semiconductor Processing | 2016
Satoshi Shindo; Yuji Sutou; Junichi Koike; Yuta Saito; Yun-Heub Song
Chemistry of Materials | 2017
Yuta Saito; Yuji Sutou; Paul Fons; Satoshi Shindo; Xeniya Kozina; Jonathan M. Skelton; Alexander V. Kolobov; Keisuke Kobayashi
Journal of Optoelectronics and Advanced Materials | 2016
Kenji Kamimura; Shinya Hosokawa; Naohisa Happo; Hiroyuki Ikemoto; Yuji Sutou; Satoshi Shindo; Yuta Saito; Junichi Koike
The Japan Society of Applied Physics | 2018
Takayuki Suzuki; Ikufumi Katayama; Yusuke Arashida; Yasuo Minami; Yuji Sutou; Satoshi Shindo; Toshiharu Saiki; Jun Takeda
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National Institute of Advanced Industrial Science and Technology
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