Kanetoshi Shibata

Pulsed corona discharge as a source of hydrogen and carbon nanotube production

Experiments are performed to develop a pulsed corona plasma system for the production of hydrogen and carbon nanotubes (CNTs), directly by methane decomposition, at atmospheric pressure (/spl sime/760 torr). The corona discharge is energized by a pulse voltage (/spl les/7 kV) with pulsewidth 12 /spl mu/s at a repetition rate of about 1 kHz. The simultaneous measurement of both hydrogen gas and CNTs within nonthermal methane discharge at atmospheric pressure are presented. The influences of argon gas on the production rate of hydrogen have also been studied. Resistivity 0.15 /spl Omega/cm of CNTs is observed with the help of a four-probe method. The structural geometry of the CNT is observed by transmission electron microscope (TEM). The soot that comes out of the discharge is collected from the cathode. The present experimental technique could be useful for the mass production of future energy source providing by hydrogen cells and the nanoelectronics.

SHEET-SHAPED PLASMA PRODUCED BY ELECTRON CYCLOTRON RESONANCE HEATING

A new production technique of sheet‐shaped plasma by means of electron cyclotron resonance heating (ECRH) is proposed. The sheet plasma is produced in a vessel with rectangular cross section set in a rectangular magnetic field coil. The maximum density and electron temperature of the sheet plasma are about 2.6×1011 cm−3 and 7 eV, respectively, in a typical argon gas pressure of P0=5×10−4 Torr. The sheet plasma has several peaks of the density profile across the plasma width. These modes appear according to the change of working gas pressure. Those parameters including plasma density, density profile, and ion energy are controllable. This plasma is expected to be useful for material processing or plasma‐based high‐energy particle accelerators.

Application of sheet shaped plasma supplemented with radio frequency plasma source for production of thin films

Production technique of thin films is described as an application of a sheet shaped electron cyclotron resonance heating plasma supplemented with a radio frequency plasma source for controlling the plasma parameters. The deposition rate of thin films onto the substrate can be varied from 6 to 102 nm/min depending on the experimental conditions under control. The thin film is made uniformly in space over a wide range of plasma parameters. The present plasma source also has typical characteristics of sharp density and temperature gradient at the edge of the sheet plasma to make a uniform, low temperature (Te⩽1 eV) plasma in the outer peripheral region. The present experimental technique could be applicable to the plasma source for material processing such as thin film formation, semiconductor devices such as solar batteries or flat panel display, and so on.

Control of plasma parameters in sheet‐shaped electron cyclotron resonance heating plasma supplemented with radio frequency discharge

Production and parameter control techniques of sheet‐shaped electron cyclotron resonance heating (ECRH) plasma are described. When rf power (f≂13.56 MHz) is supplemented by the sheet‐shaped ECR plasma, the ion temperature, Ti, ion fluxes, nb/n0, and high energy component, ei, of ions deposited to the substrate can be controlled arbitrarily within the range of 0.3 eV≤Ti≤10.0 eV, 0≤nb/n0≤30%, and 0≤ei≤60 eV, respectively, in the neutral Ar gas pressure, 4×10−4≤p≤3×10−3 Torr. Furthermore, the ion energy and/or the ion flux flowing onto the substrate could be well controlled by changing the bias voltage supplied to the substrate holder. We can expect that the present experimental technique could be applied to the material processing in a well‐defined manner.

Characteristics of electron cyclotron resonance plasma generated in a rectangular waveguide by high-power microwave

A new source for the generation of overdense plasma is developed using an electron cyclotron resonance (ECR) technique in a rectangular waveguide by a high-power (1 kW) microwave of frequency 2.45 GHz. The characteristics of the plasma for Ar gas are presented, including a large surface area to fill the entire waveguide of length 100 cm with uniformity ±3% over 50 cm. With the help of a Langmuir probe, plasma density about 1012 cm−3 and electron temperature of 8–12 eV are observed, and their dependence on the background gas pressure and magnetic field are also examined. It is shown that these parameters can be controlled by adjusting the gas pressure, magnetic fields, and/or microwave power. Such a plasma could be useful in plasma processing and in background plasma for the concept of plasma-based particle accelerators as well.

Production of Nb thin film by ECR sheet plasma

The production technique of thin film is described by using sheet-shaped electron cyclotron resonance heating (ECRH) plasma supplemented with RF plasma source for controlling the plasma parameters. The deposition rate of thin film onto the substrate can be varied from 6 to 102 nm/min depending on the experimental conditions. The thin film is almost uniformly formed over the wide range of plasma parameters. The present experimental technique can be applied to the plasma source for material processing such as thin film, semiconductor devices, and so on.