2004 Fiscal Year Final Research Report Summary
Physical Properties of Endohedral Metallo fullerenes at solid, thin film and nano-scale.
| Project/Area Number |
15350089
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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 |
Functional materials chemistry
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
KUBOZONO Yoshihiro OKAYAMA UNIVERSITY, Graduate School of Natural Science and Technology, Associate Professor, 大学院・自然科学研究科, 助教授 (80221935)
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| Co-Investigator(Kenkyū-buntansha) |
IWASA Yoshihiro Tohoku University, Institute for Materials Research, Professor, 金属材料研究所, 教授 (20184864)
TAKAYANAGI Toshio OKAYAMA UNIVERSITY, Graduate School of Natural Science and Technology, Research Associate, 大学院・自然科学研究科, 助手 (50263554)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Endohedral Metallofullerenes / Solid State Physics / Thin-film Devices / Nanostructure / Scanning Tunneling Microscope / Single Molecule Manipulation |
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| Research Abstract |
The structures and electronic properties of endohedral metallofullerenes and higher fullerenes have been studied at solid, thin-film and nanometer scale. The crystal structures of M@C_<82>(Dy,Ce and Pr) and C_<82> have been determined to be simple cubic (Pa3) by Rietveld refinements for X-ray diffraction patterns with synchrotron radiation. The first-order structural phase transition was observed for the crystals of M@C_<82> around 150 K. Furthermore, Rb_<8.8(7)>C_<84> was prepared by doping Rb metal into the crystals of C_<84>, and the X-ray diffraction pattern showed the simple cubic structure of Pa3. The temperature-dependent ESR spectra suggested a metallic behavior for Rb_<8.8(7)>C_<84>.
The resistivity and optical absorption spectra for M@C_<82>,C_<82> and C_<84> showed that these compound are not metals but normal semiconductors with small gap. The gap estimated from resistivity was 1/2 of the optical gap. Therefore the gap estimated from resistivity was concluded to be mobility
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gap. The thin-film field-effect transistors (FETs) have been fabricated with M@C_<82>,C_<82>,C_<84> and C_<88>. These FETs showed n-channel normally-on FET properties. The field-effect mobility of C_<88> FET reached to 〜10^<-2> cm^2 V^<-1> s^<-1>, whose value was the second highest value among the fullerene FETs. The normally-on properties for endohedral metallofullerens and higher fullerenes originate from high bulk current which flow in all region of thin films.
The scanning tunneling microscope(STM) showed clear images of local structures of M@C_<82> inclusive of internal structures. The growth of M@C_<82> on well-defined Si(111)-(7 x 7) surfaces has been fully studied by the STM, and the Stranski-Krastanov type growth was found for M@C_<82>. The M@C_<82> molecules in the first layer are strongly bound on the Si surface through the chemical bond between C atoms and dangling bonds of Si adatoms. The M@C_<82> molecules above the first layer aggregate by van der Waals force between molecules. The close-packed structures of M@C_<82> have been formed by annealing the Si substrates covered with multilayer of M@C_<82> at 200℃.
The removals and movements of C_<60> molecules in the close-packed layer of C_<60> have been achieved at single molecular precision by field evaporation with the STM tip. The pin-point shooting from the STM tip enables ones to draw nano-scale characters, pictures and patterns consisting of molecular size voids. Because of technical simplicity, the free controllability, and 1 nm size of voids, this technique is widely applicable to nanoscale manufacture. Thus much information of the structures and physical properties of endohedral metallofullerens and higher fullerenes has been obtained, and the applications towards thin-film FET devices and molecular electronics have been tried based on the obtained information. Less
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Research Products
(15 results)
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[Journal Article] Electronic properties for the C_<2V>, and C_S isomers of Pr@C_<82> studied by Raman, resistivity, and scanning tunnering microscopy/spectroscopy2004
Author(s)
T.Hosokawa, S.Fujiki, E.Kuwahara, Y.Kubozono, H.Kitagawa, A.Fujiwara, T.Takenobu, Y.Iwasa
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Journal Title
Chem.Phys.Lett. 395
Pages: 78-81
Description
「研究成果報告書概要(欧文)」より
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