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Resistance Switching in View of Electron Hole Dynamics in Ferroelectric Related Oxides
Yukio Watanabe,Daisuke Matusmoto,Mizuki Yamato,Shigeru Kaku 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
An examination of typical switching experiments shows that the performances of the resistance switching in transition-metal oxides vary widely and depend on the details of each experiment. Conventional defect mechanisms, such as oxygen vacancies, work in some experiments. However, by comparing the macroscopic and the nanometer-scale characteristics and switching, we show here that other experiments indicate the possible existence of a more intrinsic physically new mechanism.VISITOR=Gzm-G
Yuichiro Watanabe,Yukio Kurihara 한국분자세포생물학회 2004 Molecules and cells Vol.17 No.2
Tobacco mosaic virus (TMV)-Cg is able to propagate and multiply systemically to high levels in Arabidopsis thaliana ecotype Col-0. In this study, we obtained a Cg mutant, Cgk1, which expresses a coat protein with a truncated carboxyl terminus. Interestingly, Cgk1 in-duced necrosis that resembled the hypersensitive re-sponse and caused more pronounced disease symp-toms than wild type Cg in Arabidopsis Col-0 plants. A reactive oxidative burst occurred prior to this necrosis. We found that expression of the pathogenesis-related gene PR-1 was induced by Cgk1 infection, and also by infection with wild type Cg, but only in npr1-2 mutant plants, not in NahG transgenic plants. These results suggested that PR-1 expression is dependent on the salicylic acid signaling pathway, but is independent of NPR1.
M. Tanamura,Yukio Watanabe,H. Kida,Naotake Toyama 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
A new approach of the ion milling is proposed, utilizing the mass selectivity of the sputtering process. As model experiments, we performed etching of conducting perovskite oxide lms that are often used as electrode of ferroelectric lms and are known to be extremely structure-sensitive. By using He, N2, Ar and Kr as an etching gas, various etching characteristics are found to depend evidently on the molecular weight of the gas. Substantial improvements are demonstrated by using Kr that has the heaviest molecular weight. To explain the results, a semi-empirical extension of Sigmund theory is proposed. The present approach provides a new way to etch metal oxides including ferroelectrics by utilizing the atomic/molecular mass eect in the sputtering.
Motochika Okano,Yukio Watanabe,Naotake Toyama 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
The dielectric and the current conduction properties of BaTiO3 epitaxial lms that posses Schottky contacts at one surface and a quasi-ohmic contacts at the other surface are measured. The dielectric constant is found to increase monotonically up to, at least, 200 C. An increase of resistance or a constant resistance is found near TC only in the reverse bias current, which would correspond to the positive temperature coecient of resistance (PTCR) eect in ceramics. The heterostructures used in the present suggest the PTCR eect as the contribution of the reverse bias conduction
Satoshi Miyauchi,Yukio Watanabe 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
BaTiO3/(La,Sr)2CuO4 multilayered lms are epitaxially grown on [001] SrTiO3 single crystals. X-ray diffractometry shows that the BaTiO3 layer is a mixture of a- and c-axis-oriented regions. The current-voltage characteristics of the lms are measured between RT and 150 C, and the temperature (T) dependence of the conductivity of the lms is deduced. The as-grown lms show mostly activation-type T-dependence of but exhibit an abrupt change typically once of twenty times. When the lms are post-annealed, the lms constantly exhibit anomalous abrupt changes in the T-dependence of
Conduction Peaking at Phase Transitions of As-grown Insulating BaTiO3 Single Crystals
Yosuke Urakami,Hirotaka Yoshioka,Yukio Watanabe 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
We have measured DC current-voltage characteristics of undoped semiinsulating BaTiO3 single crystals and found that the dc conductance dened by the measurements peaks at all three ferroelectric phase transitions of BaTiO3. The peaks are evident in crystals that possess a low coercive eld EC and have, in most cases, the spontaneous polarization component perpendicular to the surface. The conductance of the crystals is typically 1 n 1cm1 at the peak of the paraelectric-ferroelectric transition and exhibits a temperature dependence different from the thermal-activation type. The present study proves that the observed peaking represents a real carrier-onduction anomaly. This anomaly can be a manifestation of a new liquid-like state of electron polarization at phase transitions.