M. Noda

Formation of graphene nano-particle by means of pulsed discharge to ethanol

Nano-graphene particles (NGPs) were deposited by a pulsed discharge (PD) to ethanol in Ar gas atmosphere of about 600 Torr. The frequency (f) of the PD was changed from 1 to 5 kHz at constant duty ratio of 20%. Evaluations of the NGPs were performed with scanning electron microscope, high resolution transmission electron microscope, and Raman spectra. When f was changed from 1 to 5 kHz, domain size of the NGPs was decreased from 34 to 19 nm. The number of the graphene layers (GLs) was decreased from about 20 to 4, though the number of GLs was scattered from 24 to 2. These results show that the domain size and the number of the GLs can be controlled with f of the PD.

Deposition of SiO2 Thin Films on Polycarbonate by Atmospheric-Pressure Plasma

Low-temperature, atmospheric-pressure SiO2 thin film deposition was achieved using dielectric barrier discharge plasma with a high-voltage pulse. Experiments were conducted using diethoxydimethylsilane as the silicon source at different oxygen concentrations, gas flow rates, and deposition times. Hard, transparent thin-coated films were obtained at high oxygen concentrations because of the capture of carbon by oxygen during deposition. A deposition rate of 60 nm/min was achieved with the pulsed plasma at a duty ratio of 4%, gap length of 1 mm, and peak voltage of 13 kV without cooling or heating of the polycarbonate substrate. A usable SiO2 hard-coat film with a thickness of 1.6 µm and an indentation hardness of 1480 N/mm2 was obtained after a deposition time of 30 min in oxygen.

Optical Emission Spectra Related to Microstructures of Diamond Film Deposited by Plasma Enhanced Chemical Vapor Deposition

Optical emission spectra from plasma during deposition of diamond film were investigated by an optic multi-channel spectrometer using a CCD array sensor. The diamond film was deposited by DC plasma enhanced (PE) chemical vapor deposition (CVD) using hydrogen and methane gas mixture, where substrate was located at near the plasma and the discharge was performed by intermittent discharge. When Pg during the deposition was increased from 50 to 250 Torr, the optical emissions of hydrogen (Hα and Hβ) and C2 were increased, and corresponding to these increases, deposition rate of the diamond film was increased and crystalline quality became superior. When Cm was changed from 1 to 3 %, the emission from C2 was increased, and whereas, the emission from hydrogen was decreased. Corresponding to these changes of the emission, the deposition rate of the film was increased and amorphous component in the deposited film was also increased. These results show that the increase of C2 results in the increase of the deposition rate, and increase of hydrogen is effective to eliminate amorphous component, and therefore, monitoring of the optical emission from hydrogen and C2 is useful for the deposition process of the diamond film.