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267. Pb-Based Ferroelectric Thin Films Prepared by MOCVD.

Author

Ascheron, Claus E., Kölsch, Hans J., Skolaut, Werner, Okuyama, Masanori, Ishibashi, Yoshihiro, Shimizu, Masaru, Fujisawa, Hironori, and Niu, Hirohiko

Abstract

This Chapter focuses on the preparation and ferroelectric properties of Pb-based thin films and nanostructures. First, the growth behavior of MOCVD-deposited PbTiO3 and PbZrxTi1-xO3 (PZT) thin films on various substrates, such as polycrystalline Pt(111)/SiO2/Si(100), SrTiO3(100) single crystals and epitaxial SrRuO3(100)/SrTiO3(100), has been investigated. SEM, AFM and TEM observations revealed that PbTiO3 and PZT showed the V-W (Volmer-Weber) growth mode when they were grown on polycrystalline Pt-covered Si substrates. From AFM observations, it was found that PZT grown on etched SrTiO3(100) with a surface terminated by TiO2 and on the TiO2 planes of annealed SrTiO3(100) showed the S-K (Stranski-Krastanov) growth mode. The V-W growth mode was also observed for PZT on the SrO planes of annealed SrTiO3(100). When PZT was grown on epitaxial SrRuO3(100)/SrTiO3(100), the S-K growth mode was observed. Epitaxial PZT ultrathin films 20 nm thick were successfully grown on SrRuO3(100)/SrTiO3(100) with a terrace and step structure. Only when PZT films were grown on SrRuO3 with a terrace and step structure did they exhibit good ferroelectric hysteresis loops, with remanent polarizations (Pr) of 29 μC/cm2 to 33 μC/cm2 and coercive fields (Ec) of 340 kV/cm to 370 kV/cm. A 15 nm-thick PZT film showing an unsaturated hysteresis loop was also studied. The ferroelectricity and local current flow of PZT ultrathin films with thicknesses smaller than 10 nm were investigated by SPM techniques. V-W growth was observed for PbTiO3 and PZT on epitaxial Pt/SrTiO3 and Pt/MgO substrates. Pyramidal-shaped, triangular-prism-shaped and square-shaped PbTiO3 and PZT self-assembled nanostructures were successfully prepared on epitaxial Pt/SrTiO3(111), (110) and (100) substrates, respectively, demonstrating structural control. Piezoresponse measurements using SPM proved that PbTiO3 and PZT nanoislands prepared on various substrates had ferroelectricity even before they became films. The minimum volume of a PbTiO3 nanostructure was 1.9 × 103 cm (38 nm width × 1.7 nm height). This result has led us to a new study and development, of self-assembled and self-organized ferroelectric nanostructure technology. [ABSTRACT FROM AUTHOR]

Published
2005

274. Cerebral swelling caused by deep venous thrombosis immediately after cranioplasty.

Author

Shimizu, Yu, Tsuchiya, Katsuhiro, and Fujisawa, Hironori

Subjects
*DECOMPRESSIVE craniectomy, *VENOUS thrombosis, *CEREBRAL edema, *THERAPEUTICS, *ORAL contraceptives, *EDEMA, *SINUS thrombosis
Abstract

Recently, different groups have reported a rare, unexplained complication of sudden death with massive cerebral oedema immediately after cranioplasty. Case presentation: A 34-year-old woman underwent decompressive hemicraniectomy after traumatic brain injury. She was reportedly on oral contraceptives. She developed massive cerebral swelling immediately after an uneventful cranioplasty. After surgery, her pupils became fixed and dilated, and brain MRI revealed massive brain oedema. Magnetic resonance venography displayed occlusion in the deep venous sinus. The oedema was believed to be caused by venous sinus thrombosis. The patient's family declined to avail any surgical and medical treatment, and the patient died on the second postoperative day. Conclusions: Fatal massive cerebral oedema is an uncommon complication after cranioplasty in patients who had previously undergone decompressive craniectomy. Our patient was using oral contraceptives and was thus susceptible to the development of venous sinus thrombosis. Neurosurgeons must be aware of the complications associated with venous sinus thrombosis and discuss it with the patients and their families. [ABSTRACT FROM AUTHOR]

Published
2023
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283. Approximate tail probabilities of the maximum of a chi-square field on multi-dimensional lattice points and their applications to detection of loci interactions.

Author

Kuriki, Satoshi, Harushima, Yoshiaki, Fujisawa, Hironori, and Kurata, Nori

Subjects
APPROXIMATION theory, PROBABILITY theory, CHI-squared test, ALGEBRAIC field theory, DIMENSIONAL analysis, LATTICE theory
Abstract

In this study, we define a chi-square random field on a multi-dimensional lattice points index set with a direct product covariance structure and consider the distribution of the maximum of this random field. We provide two approximate formulas for the upper tail probability of the distribution based on nonlinear renewal theory and an integral-geometric approach called the volume-of-tube method. This study is motivated by the detection problem of the interactive loci pairs which play an important role in forming biological species. The joint distribution of scan statistics for detecting the pairs is regarded as the chi-square random field above, and hence the multiplicity-adjusted $$p$$ -value can be calculated using the proposed approximate formulas. By using these formulas, we examine the data of Mizuta, Harushima and Kurata (Proc Nat Acad Sci USA 107(47):20417-20422, ) who reported a new interactive loci pair of rice inter-subspecies. [ABSTRACT FROM AUTHOR]

Published
2014
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284. Evolutionarily Diverged Regulation of X-chromosomal Genes as a Primal Event in Mouse Reproductive Isolation.

Author

Oka, Ayako, Takada, Toyoyuki, Fujisawa, Hironori, and Shiroishi, Toshihiko

Subjects
X chromosome, SPERMATOGENESIS in animals, ANIMAL models in research, DNA microarrays, MEIOSIS
Abstract

Improper gene regulation is implicated in reproductive isolation, but its genetic and molecular bases are unknown. We previously reported that a mouse inter-subspecific X chromosome substitution strain shows reproductive isolation characterized by male-specific sterility due to disruption of meiotic entry in spermatogenesis. Here, we conducted comprehensive transcriptional profiling of the testicular cells of this strain by microarray. The results clearly revealed gross misregulation of gene expression in the substituted donor X chromosome. Such misregulation occurred prior to detectable spermatogenetic impairment, suggesting that it is a primal event in reproductive isolation. The misregulation of X-linked genes showed asymmetry; more genes were disproportionally downregulated rather than upregulated. Furthermore, this misregulation subsequently resulted in perturbation of global transcriptional regulation of autosomal genes, probably by cascading deleterious effects. Remarkably, this transcriptional misregulation was substantially restored by introduction of chromosome 1 from the same donor strain as the X chromosome. This finding implies that one of regulatory genes acting in trans for X-linked target genes is located on chromosome 1. This study collectively suggests that regulatory incompatibility is a major cause of reproductive isolation in the X chromosome substitution strain. [ABSTRACT FROM AUTHOR]

Published
2014
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297. Assessment of polarization-related band modulation at graphene/Mn-doped BiFeO3interfaces by photoemission electron microscopy

Author

Nakashima, Seiji, Ito, Tatsuya, Ohkochi, Takuo, and Fujisawa, Hironori

Abstract

Recently, ferroelectric semiconductors has become a subject of interest with regard to potential applications in novel electronic and opto-electric devices. One of the most important aspects of employing these materials is band modulation based on spontaneous polarization to generate polarization charges acting as quasi-dopants at metal/ferroelectric and ferroelectric/ferroelectric interfaces. The present study fabricated graphene/Mn-doped BiFeO3(BFMO)/SrRuO3/SrTiO3(001) capacitor structures with the BFMO having either upward or downward polarization. Band modulation at the graphene/BFMO interface as a result of polarization charges was evaluated using photoemission electron microscopy on the BL17SU beamline at the SPring-8 facility, Japan. The chemical shifts observed in Bi 4f and C 1s XPS spectra indicated that positive (negative) polarization charges acted as quasi-dopants for electron (hole) doping of the BFMO and graphene.

Published
2022
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