Establishment of innovational materials surface treatment / modification technology with using supercritical cluster plasma fluid

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(A) We generated micrometer-scale discharge plasma in high-pressure H_2O and Xe up to supercritical conditions. In our previous paper, we reported the existence of two peculiar features in the breakdown voltages under high-pressure CO_2. The first one was the downward shift at the right-hand side of Paschen's curve above about 2.5 MPa, and the second one was the drastic decrease in the breakdown voltages near the critical point. We have experimentally confirmed that these features are also observed in H_2O and Xe, even though there are some differences among these materials. Our theoretical fitting involving a density fluctuation term ED agrees well with the experimental results, especially for Xe. We suppose that these unique features are brought about by decreases in the electron-to-particle cross section □, ionization potential □_i, and secondary electron coefficient □', and changes in the discharge space.(B) We diagnosed the inner state of the supercritical CO_2-DBD (dielectric bar … More rier discharge) plasma by micro-Raman spectroscopy. From Raman band of CO_2 near 1388 cm' inside the plasma, the large-wavenumber shift, which correspond to a decrease of CO_2 density was not observed. It was also found that the Raman band obtained from CO_2 with the plasma showed a local shift near the critical point, comparing with other high-pressure condition.(C) Under an optimal condition, dense Cu-carbon composite films were successfully deposited by dielectric barrier discharge method in sc-CO_2 and Ar. Diagnostics of DBD generated in scCO_2 and scAr was conducted. From V-I measurement, the negative charge density of our SCF plasma was estimated to be more than 10^<18> cm^<-3>, which shows that our SCF plasma has a high density of ions and electrons, which are required for obtaining a highly reactive plasma. Cu/C films were successfully obtained and its dependence on power frequency and applied voltage was studied. Cu content of films obtained in an scCO_2 and scAr was about 10 % and 60 % maximum, respectively. This result suggests the advantage of Ar in terms of the fineness of synthesized materials. The deposition rate was about 300 nm/min in scCO_2 and 190 nm/min in scAr. These results suggest the potential of an SCF plasma processing for realization of high-speed metal film deposition. Moreover, strip-line microwave micro plasma was also generated, in which substrate conditions, such as temperature and distance from plasma, can be controlled independently of plasma. Less