High-efficient production methods of microplasma using nano-size-structured and active-functional electrodes

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For efficient production of micro-plasma, nano-size-structured and/or active-functional electrodes have been developed. It is expected that the plasma-surface interaction, especially on the electrode providing electrons, will be important to sustain micro-size plasma due to its large ratio of the surface area to the volume.In this research, it has been examined to use diamond with excellent material properties and carbon nanotubes (CNTs) with fine nano-structures. We have succeeded to fabricate CNTs on diamond nano-whiskers for cathode material with highly improved electron field emission property. It was confirmed that the breakdown voltage in a micro-gap discharge were extremely higher than the conventional gas discharge due to small probability of ionization by cosmic ray. By using CNTs for cathode, the breakdown voltage was successfully decreased.It was proposed that with using excellent field emission material for cathode in a higher pres-sure more than 1MPa with a smaller electrode gap below 10 μm, it would make field emission electron excited microplasma. The challenge to sustain microplasma by the continuous field emission has not been demonstrated successfully because of difficulty in controlling the small gap in the high pressure. However, some important experimental parameters have been clarified.It was also demonstrated that microplasma was produced locally in a SEM chamber with in-situ observation of the specimen. For the local gas injection in the differentially pumping, it was suitable to use a small orifice as a gas nozzle. The microplasma process in SEM will be useful for local recovery of integrated circuits and fabrication of micro devices. LF (low frequency) microplasma jet using Ar gas instead of conventional He was also studied by time-spatial resolved optical emission spectroscopic measurements. It was succeeded to sustain stable microplasma jet also with Ar and the generation mechanism for LF jet was mostly clarified.