Haruka Suzuki

Desorption behavior of zinc atoms from zinc-sulfate solution irradiated with pulsed DC plasma

A DC pulsed plasma ignited between a metal needle and zinc sulfate (ZnSO4) solution electrode was used to investigate Zn metal desorption from an electrolyte solution. Using an ICCD camera and optical band-pass filter, 2D atomic absorption spectroscopy was carried out during irradiation of pulsed plasma to the surface of the solution. The time-resolved measurement of Zn atoms released to the gas phase revealed that the Zn desorption rate monotonically increased with increasing number of discharge repetitions. The surface temperature of the electrolyte solution was observed with a thermographic camera, and correlations between the H2O and Zn desorption rate were inspected. The correlation between the H2O and Zn desorption rate suggested that Zn desorption is assisted not only by the electric field of the discharge but also by H2O evaporating from the solution.

Low-pressure sustainment of surface-wave microwave plasma with modified microwave coupler

Sustainment of long-scale surface-wave plasma (SWP) at pressures below 1 Pa is investigated for the application of the SWP as an assisting plasma source for roll-to-roll sputter deposition. A modified microwave coupler (MMC) for easier surface-wave propagation is proposed, on the basis of the concept of the power direction alignment of the slot antenna and surface-wave propagation. The superiority of the MMC-SWP over conventional SWPs is shown at a sustainment pressure as low as 0.6 Pa and an electron density as high as 3 × 1017 m−3. A polymer film is treated with the MMC-SWP at a low pressure of 0.6 Pa, and surface modification at a low pressure is proved using Ar plasma. These results show the availability of the MMC-SWP as the surface treatment plasma source that is compatible with sputter deposition in the same processing chamber.

Magnet-free uniform sputtering of dielectric film by RF and microwave power superposition

A novel sputtering device that is free of magnets (magnet-free surface wave sputtering plasma: MF-SSP) is developed by combining a surface wave plasma and RF bias power. Low-pressure (<0.5 Pa) plasma sustainment is demonstrated by MF-SSP with a uniform sputter deposition rate with a deviation of less than 5% within an area of 10 × 10 cm2. Highly oriented MgO films are deposited at a substrate temperature of 200 °C.

New line plasma source excited by 2.45 GHz microwave at atmospheric pressure

A new device for the production of atmospheric-pressure microwave line plasma is proposed. By using a loop-structure waveguide and a circulator, only traveling waves transmitted in the waveguide are superimposed in phase with each other by impedance matching of an EH tuner. The spatiotemporal behavior of the plasma and the spatial distribution of the emission intensity were investigated using a high-speed camera and a digital still camera. A stable discharge is sustained inside a slot of 60 cm length and 0.1 mm width in pure helium gas at a microwave power of 1.0 kW in the cw mode.

An approach to line-shaped nitrogen plasma production at atmospheric pressure by slot-excited microwave discharge

For large-area surface treatment processing at atmospheric pressure, a one-dimensional line-shaped plasma source using molecular gas discharge excited by a 2.45 GHz microwave was investigated. From the results of three-dimensional microwave simulation, a flat waveguide is proposed to increase the power density for the enhancement of the electric field inside the slot and easy breakdown and sustainment without markedly increasing the input power. A pure N2 plasma of submeter length was produced by a travelling wave of CW microwave power using the flat waveguide with a narrow-gap slot of 30 cm length incorporated into the loop waveguide system to suppress standing waves. The plasma length was increased by increasing the input microwave power from 1.0 to 2.5 kW and its maximum was about 14 cm. The medium gas temperature of 1100 K was measured from the rotational temperature of the N2 second positive band evaluated by optical emission spectroscopy.