Y. Suda

Effect of temperature, pressure, and gas ratio of methane to hydrogen on the synthesis of double-walled carbon nanotubes by chemical vapour deposition

Double-walled carbon nanotubes (DWCNTs) were synthesized by chemical vapour deposition using Fe–Mo catalyst supported on magnesium oxide particles. A mixture of gases of methane and hydrogen was used for the growth. The effect of gas pressure, ratio of methane to hydrogen, and growth temperature on the structure, purity, and yield of DWCNTs has been studied in detail. Transmission electron microscope studies revealed that the growth temperature is the crucial factor determining the size of the catalyst particles. Scanning electron microscope studies were also carried out to provide information on the purity and diameter of DWCNTs synthesized under various conditions.

Amorphous fluorocarbon polymer (a-C:F) films obtained by plasma enhanced chemical vapor deposition from perfluoro-octane (C8F18) vapor I: Deposition, morphology, structural and chemical properties

The method of obtaining amorphous fluorocarbon polymer (a-C:F) films by plasma enhanced chemical vapor deposition in a capacitively coupled, 13.56 MHz reactor, from a new monomer, namely perfluoro-octane (C8F18) vapor, is presented. For monomer pressure ranging from 0.2 to 1 Torr and input power density from 0.15 to 0.85u2009W/cm3, the maximum deposition rate reached 300 nm/min, while 10% monomer dilution with argon led to a deposition rate of 200 nm/min. The film surface and bulk morphologies, chemical and structural compositions were investigated using scanning electron microscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. It was revealed that the films have a dense and compact structure. The fluorine to carbon ratio (F/C) of the films was between 1.57 and 1.75, and the degree of cross-linking was between 55% and 58%. The relative amount of perfluoroalkyl (CF2) groups in the films was 29%. The FTIR spectra showed absorption bands corresponding to the different vibrationa...

Migration-assisted Si subatomic-layer epitaxy from Si2H6

Submonolayer by submonolayer Si epitaxy (subatomic-layer epitaxy, SALE) from Si2H6 on Si(001) has been successfully realized independent of the adsorption coverage by repeating self-limited Si2H6 adsorption and surface adatom migration induced by surface thermal excitation with Ar+ laser irradiation and self-resistive heating. With the self-limited Si2H6 adsorption and the migration assist, a substrate temperature window and a laser power window with a constant growth rate and an atomically flat surface have been obtained. The fact conversely indicates that the surface temperature control within the limited temperature range is important during the thermal excitation to obtain the atomical surface flattening. On the basis of the results of the reflection high-energy electron diffraction study on a Si2H6/Si(001) system together with the SALE growth experiments, models for the SALE growth mechanisms and the growth modes are proposed.

Carbon nanotube growth on metal-catalyzed substrates in a laser oven apparatus

Carbon nanotubes (CNTs) were grown on Ni- and Fe-coated SiO 2 /Si substrates in a laser oven apparatus. The grown CNTs were analyzed by scanning electron microscopy. It is speculated that the CNTs grow out from the metal nanoparticle after laser-ablated carbon clusters have been dissolved in it. In a range of oven temperatures between 800 and 1100°C, growth of CNTs was achieved at a temperature ≥ 1000°C. The thickness of the Ni film controlled the CNTs diameter.