2006 Fiscal Year Final Research Report Summary
Study on the Fabrication of Ferroelectric Ultrathin Films and Nanostructures by MOCVD and Their Size Effects
| Project/Area Number |
17360144
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | University of Hyogo |
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Principal Investigator |
SHIMIZU Masaru University of Hyogo, Graduate School of Engineering, Professor, 大学院工学研究科, 助教 (30154305)
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| Co-Investigator(Kenkyū-buntansha) |
HONDA Koichiro Fujitsu Laboratories Ltd, Device Materials Laboratories, Research Fellow, 基盤技術研究所, 主幹研究員 (60399730)
FUJISAWA Hironori University of Hyogo, Graduate School pf Engineering, Assistant Professor (30285340)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Size Effect / PbTiO_3 Ultrathin Films / PbTiO_3 Nanoislands / MOCVD / Piezoresponse Force Microscopy / Critical Thickness / Phase Transition Temperature / Synchrotron X-Ray Diffraction |
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| Research Abstract |
In order to investigate the size effect in ferroelectric thin films and nanoisland structures, PbTiO_3 ultrathin films and nanosilands were fabricated by MOCVD and their structureal nature and ferroelectric properties were studied.
1) Epitaxial PbTiO_3 ultrathin films with thicknesses of 10-0.9nm were successfully grown on SrRuO_3/SrTiO_3 by MOCVD.
2) Piezoresponse measurements using Piezoresponse Force Microscopy (PFM) and observation of ferroelectric polarization using scanning nonlinear dielectric microscopy (SNDM) evidently proved the presence of ferroelectricity in PbTiO_3 ultrathin films with a thickness of 1.3nm (3 mono layers (ML)). Ferroelectrcity was not observed in the 0.9nm (2.2 ML) -thick film. In our experiment, critical thickness was 1.3nm.
3) PbTiO_3 and PZT nanoislands were successfully fabricated on Pt/SrTiO_3 substrates by self-assembly using MOCVD. Three types of islands (pyramidal-shaped, triangular-prism-shaped and square-shaped islands) were grown on Pt/SrTiO_3(111), (110) and (001), respectively.
4) PFM measurement proved the presence of ferroelectrcity in the PbTiO_3 nanoisland with a width of 27nm and a height of 1.2nm.
5) Phase transition temperatures of PbTiO_3 nanoislands on Pt/SrTiO_3(111) and (110) were measured by Raman spectroscopy. From Raman measurement, it was fond that phase transition temperatures in pyramidal-shaped islands and triangular-prism-shaped islands decreased as island size decreased.
6) Crystal structure of the nanosiland on Pt/SrTiO_3(111) was investigated using Synchrotron X-ray diffraction. As island size decreased, the c-axis lattice constant decreased at sizes smaller than 100nm though the a-axis lattice constant did not changed.
7) Nano-sized Au dots were successfully fabricated by self-assembly. Using these Au nanodots as a top electrode, I-V characteristics of PbTiO_3 nanosilands on Pt/SrTiO_3 were measured.
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