Showing papers by "Kiyoshi Yase published in 1994"
Patent•
01 Aug 1994
TL;DR: Carbon nanotubes are isolated from a mixture of graphite particles by a process including the steps of: finely pulverizing the mixture, dispersing the pulverized product in a liquid medium, and centrifuging the resulting dispersion to obtain a supernatant containing carbon and graphite having a particle size of 0.3 μm or less as discussed by the authors.
Abstract: Carbon nanotubes are isolated from a mixture containing the carbon nanotubes and graphite particles by a process including the steps of: finely pulverizing the mixture; dispersing the pulverized product in a liquid medium; centrifuging the resulting dispersion to obtain a supernatant containing carbon nanotubes and graphite particles having a particle size of 0.3 μm or less; separating the supernatant into a solid phase and a liquid phase; and calcining the solid phase in an oxygen-containing atmosphere at a temperature sufficient to burn the graphite particles and to leave the nanotubes.
103 citations
TL;DR: In this paper, the electronic properties of purified carbon nanotubes were examined based on the electron spin resonance (ESR) spectroscopy and it was shown that the purified nanotube is a clean semiconductor almost without magnetic impurity and is doping inactive.
44 citations
TL;DR: A charge transfer complex of tetrathiafulvalene and tetracyano-quinodimethane (TTF-TCNQ) is vacuum-deposited onto air-cleaved (001) planes of alkali halides, NaCl, KC1 and KBr.
Abstract: A charge transfer complex of tetrathiafulvalene and tetracyano-quinodimethane (TTF-TCNQ) is vacuum-deposited onto air-cleaved (001) planes of alkali halides, NaCl, KC1 and KBr. The molecular orientation in thin films and surface morphology are characterized by transmission electron microscopy (TEM), and scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to confirm the fine structure and dependence of nucleation and crystal growth on the kinds of substrate.
21 citations
24 Jul 1994
TL;DR: In this paper, single crystals and thin films deposited on alkali halides of one-dimensional organic conductor, tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), by scanning tunneling microscope (STM), were similar and the I-V (tunneling current) curves measured were both metallic at room temperature.
Abstract: We have studied single crystals and thin films deposited on alkali halides of one-dimensional organic conductor, tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), by scanning tunneling microscope (STM). The molecular structures of both samples imaged by STM were similar and the I-V (tunneling current—bias voltage) curves measured were both metallic at room temperature. However, when thin films were cooled from room temperature, some parts of films showed to be insulating at ≈200K which is much higher than the critical temperature of the metal-insulator phase transition which was observed for the bulk single crystal (53K). The results may suggest that the charge density wave occurs at higher temperature in thin films as in the case of (BEDT-TTF) 2 I 3 films.
14 citations
TL;DR: In this article, the nucleation mechanism of C60 was confirmed in the sense of crystal growth, and it was found that the island crystals on KC1 tended to be especially created on the center of adjacent terraces and at the edge of surface step, and these distance between the neighboring islands depended on the width of terrace and substrate temperature.
Abstract: To fabricate ultrathin films of fullerene (C60) without any dislocation and stacking faults, nucleation and crystal growth during deposition should be precisely controlled. Slow evaporation of C60 onto the (001) planes of alkali halides, NaCl, KC1 and KBr, and mica kept at higher temperature, leads the discrete nucleation, whose distances between the adjacent small crystals depended on the substrate temperature and the kinds of substrates. It was found that the island crystals on KC1 tended to be especially created on the center of adjacent terraces and at the edge of surface step, and these distance between the neighboring islands depended on the width of terrace and substrate temperature. The nucleation mechanism of C60 was for the first time confirmed in the sense of crystal growth.
9 citations
TL;DR: In this paper, a stable Langmuir monolayer on a pure water subphase when the counter cation is chosen so as to enhance the hydrophobic character of this amphiphilic coordination compound was shown.
8 citations
TL;DR: In this article, a long chain compound, calcium stearate ((CH 3 (CH 2 ) 16 CO 2 ) 2 Ca), is evaporated on the substrates of KCl, mica and amorphous carbon film, it forms either slender or planar crystals depending on the deposition conditions, in which molecules arrange parallel or perpendicular to the surface.
7 citations
TL;DR: In this article, a long chain compound, calcium stearate ((CH 3 (CH 2 ) 16 CO 2 ) 2 Ca), was vacuum-deposited onto an amorphous carbon film kept at 0°C to form plate-like crystals.
6 citations
24 Jul 1994
TL;DR: In this article, the electronic properties of purified carbon nanotubes were examined based on the electron spin resonance (ESR) spectroscopy and it was shown that the purified nanotube is a clean semiconductor almost without magnetic impurity and is doping inactive.
Abstract: The electronic properties of purified carbon nanotube (multicylinder structure with an outer diameter of ≈ 20 nm and a length of ≈ 10 μm) was first examined based on the electron spin resonance (ESR) spectroscopy. By the Raman scattering measurement, only one peak at 1581 cm −1 similar to that of graphite was found. The purified nanotube was almost ESR silent as well as the K- and the I 2 -doped samples. This indicates that the purified nanotube examined in the present study is a ‘clean’ semiconductor almost without magnetic impurity and is doping inactive.
5 citations
24 Jul 1994
TL;DR: In this paper, the nucleation process of Tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) on three kinds of alkali halides is quantitatively studied by use of atomic force microscope (AFM).
Abstract: Nucleation process of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) on three kinds of alkali halides is quantitatively studied by use of atomic force microscope (AFM). The sizes of the smallest nuclei observed for the TTF-TCNQ film grown on alkali halides at the substrate temperature of 20°C and the molecular flux of 1 × 1018 [molecules/m2 .s] were larger than several 10 nm. The deposition time of several ten seconds were necessary for the generation of these nuclei and that depended on the kind of substrates. The reasons why such a long period for the growth of the nuclei is necessary are discussed on basis of AFM observation.
4 citations