Akiko Goto

Field emission and structure of aligned carbon nanofibers deposited by ECR-CVD plasma method

Abstract Aligned carbon nanofibers and hollow carbon nanofibers were grown by MW ECR-CVD method using methane and argon mixture gas at a temperature of 550°C. The carbon nanofibers and the hollow carbon nanofibers were deposited perpendicularly on Si substrates and on Si substrates coated with Ni catalyst, respectively. From TEM analysis the diameter and length of the nanofibers are approximately 60 nm and 15 μm, respectively. Raman spectra of these aligned carbon nanofibers showed new bands of 1340 and 1612 cm−1 of the first-order Raman scattering and 2660, 2940 and 3220 cm−1 of the second-order Raman scattering. The second-order Raman scattering bands were assigned to two overtone and one combination bands on the basis of a similar assignment of micro-crystal graphite by Nemanich and Solin. By the measurement of XPS C1s band energies of 284.6 eV for the carbon nanofiber and 284.7 eV for the hollow carbon nanofiber indicate mainly sp2 carbon component in the inclusion of a small amount (

The structure and tribological property of amorphous carbon and carbon nitride films prepared by ECR plasma sputtering method

Abstract Amorphous carbon and carbon nitride (CNx) films were deposited by using the ECR plasma sputtering method. The films were deposited on a silicon substrate at room temperature by the sputtering of a carbon target by argon and argon/nitrogen ion plasma. The properties of films were investigated by XPS, Raman, SEM, and tribological measurements. The maximum of nitrogen content was N/C=0.6 in the film deposited in a nitrogen atmosphere. The friction coefficient of deposited films increased with increasing of nitrogen content. The CSS test of ultra-thin films on an Al/TiC slider with a Si intermediate layer (2 nm) indicates that a 5-nm thickness film of carbon nitride has the most significant toughness for a magnetic head.

Synthesis and characterization of graphite-like B-C-N materials of composition CNx(BN)y (x « 1, y ≤ 1)

Various graphite-like B–C–N materials were synthesized in the precursor pyrolysis system of boron trichloride and nitrogen-containing materials such as heptaazaphenalene derivatives, carbodiimides, amines, nitriles and cyanamides. The materials obtained were described with a formula of CNx(BN)y and CBx(BN)y consisting of CNx and (BN)y segments. A combination of chemical decomposition and structural analysis elucidated that the segment structure of CNx(BN)y contains local bonds of (–CC–)n–N, B–N–C and B–N pairs but no C–B bonds. A miscible blend structure model was expected by analogy with hybrid materials. Compositions and yields of the materials were closely related to the properties of chemical reaction, nitrogen evolution and graphitization of the starting materials. In particular, B–C–N materials with high BN content were prepared in small quantities from the heptaazaphenalene polymers, and the materials with low BN content were produced from teteracyanoethylene in nearly 100% yield. The materials were oxidized to boron oxide from 500 °C to 950 °C, however, under an inert atmosphere they were stable to at least 1200 °C.

Synthesis of heterofullerene using a direct BN substitution reaction of fullerene

Abstract A heterofullerene in which carbon atoms of the fullerene cage are substituted by heteroatoms (boron and nitrogen) was synthesized by BN substitution reaction of fullerene C 60 upon irradiation with a KrF excimer laser at room temperature. The products were purified by a high performance liquid chromatography and analyzed with a double focusing mass and mass/mass spectrometer, revealing that BNC 58 ( m / z 721) was formed. The existence of boron and nitrogen in the product was confirmed by X-ray photoelectron spectroscopy and 13 C NMR analyses. Moreover, 11 B NMR spectrum of the sample indicated the existence of BN bond in the compound.

BN substitution reaction of fullerene using an excimer laser irradiation

Abstract A heterofullerene in which carbon atoms of the fullerene cage are substituted by heteroatoms (boron and nitrogen) was synthesized by a BN substitution reaction of fullerene C 60 upon irradiation with a KrF excimer laser at room temperature. The products were purified by a high performance liquid chromatography and analyzed with a double focusing mass spectrometer, revealing that BNC 58 ( m/z 721) was formed. The existence of boron and nitrogen in the product was confirmed by X-ray photoelectron spectroscopy analysis.

Nanostructural properties of pyrolytic carbon from polyacetylene thin film

Carbonization of polyacetylene thin films was carried out by means of pyrolysis at a temperature of 800°C in a vacuum. During the pyrolysis, inadiation of an electron beam was carried out for a specimen. Nanostructural properties of the pyrolytic carbon were investigated using mainly electron microscopy. Ribbon-shaped graphite crystals in nanometer size were obtained. Effects of the electron beam irradiation on the formation of carbon crystals will be discussed.

The characterization of nanocrystal graphite films deposited by ECR plasma sputtering

Abstract We investigated the deposition of carbon films at the condition of high plasma density using ECR plasma sputtering. High density of plasma with low electron temperature was obtained in the neighborhood of the substrate by the control of the magnetic flux density. The nanocrystal graphite in size less than 60 nm was deposited on the Si(1 0 0) substrates by the sputtering of graphite target in argon atmosphere at room temperature. The nanocrystal graphite films deposited at high plasma density (5.0×1011 cm−3) and low pressure (1.2×10−1 Pa) showed good tribological properties. New Raman peaks of G band were obtained. From the analysis of XPS, the nanocrystal graphite gives C1s binding energy of 284.8 eV. The electrical resistivity of the films was 10−2 Ω cm.

Structural properties of carbon materials from the electrochemical reduction of fluorinated naphthalene pitch

Abstract Synthesis of carbon materials from fluorinated naphthalene pitch has been carried out by means of electrochemical reduction. Structural and morphological properties of synthesized carbons were investigated using X-ray photoelectron spectrum (XPS), Raman scattering spectrum, X-ray diffraction measurements and scanning and transmission electron microscopy (SEM and TEM). Furthermore, a change in the structure of synthesized carbons with an electron beam irradiation was examined. The synthesized carbon has a disordered structure composed of fragments of the sp2 hexagonal network, and also has lots of micro-voids. A carbyne-like structure was found only a little with the reduction of fluorinated naphthalene pitch by Raman spectra. A lot of ribbon-like graphite nanocrystal was formed by irradiation of an electron beam at a high temperature to the defluorinated carbon. Bending of a long ribbon-like crystal of graphite was often observed. Formation mechanism of graphite nanocrystals was discussed.

Structure formation of nanoribbon graphite from carbyne-like carbons

Fluorinated carbons were reduced and defluorinated by means of electrochemical reduction . A Raman spectrum of these defluorinated carbon specimens showed that they have sp bonds. An electron beam was irradiated to these carbyne-like specimens at 800°C. This irradiation was carried out in a transmission electron microscope at accelerating voltage of 300KV. Carbyne-like carbons were almost amorphous. After the irradiation of electron beam at 800°C, small graphite crystals were observed in the form of a ribbon several nanometer in wide. The formation of the nanoribbon graphites will be discussed.