Research in the Shinohara group
on nano-structured materials

Overview

A model structure of metal containing fullerenes
inserted in single-wall carobon nanotube

Since today's device engineering is facing technical and economic difficulty in further miniaturizing electronic devices with the current fabrication technologies, the need for alternative device-channels is particularly imminent. Fullerenes and carbon nanotubes have been considered as one of the most promising nano-materials in today's nanoscience and nanotechnology since Kraetschmer and Huffman's first report on the macroscopic synthesis of C60 in 1990. In fact, fullerenes and carbon nanotubes have been successfully used for nanometer-sized devices such as diodes, transistors, and random memory cells during the past several years. During the past decade, we have been trying to elucidate structures and electronic properties of the so-called nano-carbon materials, such as fullerenes, endohedral metallofullerenes, carbon nanotubes and nano-peapods.

Synthesis, characterization and applications of endohedral metallofullerenes

The structures of endohedral metallofullerenes have been studied by using 13C NMR, UHV-STM/STS (scanning tunneling microscopy/spectroscopy) and synchrotron X-ray diffraction. For example, we have synthesized and characterized for the first time "metal-carbide" metallofullerenes such as (Sc2C2)@C84 and (Y2C2)@C82 and found that a C2 cluster is encapsulated in Sc2@C84 and Y2@C82, respectively. This is the first example that C2 radical is trapped in a molecule. Furthermore, our recent UHV-STM/STS studies show that metallofullerenes do not rotate at temperatures below 50 K on Si(100)2 × 1 hydrogen-terminated clean surfaces.

Selected relevant publications
"Element-Specific Magnetic Properties of Di-Erbium Er2@C82 and Er2C2@C82 Metallofullerenes: A Synchrotron Soft X-ray Magnetic Circular Dichroism Study"
H. Okimoto et al., J. Phys. Chem. C 112, 6103-6109 (2008)

“Enhanced 1520 nm Photoluminescence from Er3+ Ions in Di-erbium-carbide Metallofullerenes (Er2C2)@C82 (Isomers I, II, and III)”
Y. Ito et al., ACS Nano 1, 456-462 (2007).

“Magnetism of the endohedral metallofullerenes M@C82 (M=Gd,Dy) and the corresponding nanoscale peapods: Synchrotron soft x-ray magnetic circular dichroism and density-functional theory calculations”
R. Kitaura et al., Phys. Rev. B 76, 172409 (2007).

Selective and high-yield synthesis of carbon nanotubes

Single-, double- and multi-wall carbon nanotubes have been synthesized selectively in high-yield by using the methods developed in our laboratory such as zeolite-CCVD (catalyst-supported chemical vapor deposition), HFCVD (hot-filament assisted CVD) and HTPAD (high-temperature pulsed arc-discharge) methods. In particular, double-wall carbon nanotubes (DWCNTs), which is the thinnest multi-wall carbon nanotubes, have been synthesized in high-yield. Since DWCNTs are the key carbon nanotubes materials in the application of field-emission display and tips for scanning probe microscopy, the synthesis of high-quality DWCNTs is particularly needed. To apply the DWCNTs synthesized in our laboratory in these rapidly growing area, we have been collaborating with various industrial companies in Japan and abroad.

Selected relevant publications
"Synthesis of single-wall carbon nanotubes grown from size-controlled Rh/Pd nanoparticles by catalyst-supported chemical vapor deposition"
K. Kobayashi et al., Chem. Phys. Lett. 458, 346-350 (2008)

"Fabrication, Purification, and Characterization of Double-Wall Carbon Nanotubes via Pulsed Arc Discharge"
H. Yoshida et al., J. Phys. Chem. C 112, 19908-19915 (2008)

“Enrichment of Small-Diameter Double-Wall Carbon Nanotubes Synthesized by Catalyst-Supported Chemical Vapor Deposition Using Zeolite Supports”
N. Kishi et al., Jpn. J. Appl. Phys. 46, 1797 (2007).

Synthesis, characterization and device applications of nanotube-peapods

Carbon nanotubes encapsulating fullerenes, metallofullerenes and other novel molecules (the so-called "peapods") have been synthesized in high-yield. Such peapods materials have been found to possess not only unique structural properties but more importantly novel electronic transport properties as revealed by HRTEM-EELS (high-resolution transmission electron microscopy/electron energy loss spectroscopy), STM/STS and FET (field effect transistors) measurements. We have found that peapods encaging metallofullerenes exhibit the bandgap modulation due to the electron transfer from metallofullerenes to carbon nanotubes. Such peapods have been applied to FET with novel device properties.

Selected relevant publications
"High Yield Synthesis and Characterization of the Structural and Magnetic Properties of Crystalline ErCl3 Nanowires in Single-Walled Carbon Nanotube Templates"
R. Kitaura, D. Ogawa et al., Nano Res. 1, 152-157 (2008)

"Fabrication of Metal Nanowires in Carbon Nanotubes via Versatile Nano-Template Reaction"
R. Kitaura, N. Imazu et al.,Nano Lett. 8, 693-699 (2008)

“Raman Spectroscopy of Size-Selected Linear Polyyne Molecules C2nH2 (n = 4-6) Encapsulated in Single-Wall Carbon Nanotubes”
D. Nishide et al., J. Phys. Chem. C 111, 5178 (2007).