Development of functional electrodes for dissociation of water molecules and its applications to the electrochemical machining procesges in ultrapure water

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Catalytic electrodes which can dissociate water molecules effectively were proposed and developed for ultraprecision electrochemical machining processes in ultrapure water. Surface carboxylated or sulfonated carbon polycrystalline electrodes were successfully prepared and etching rate of 8nm/s was obtained far etching of Cu polycrystalline surface using these surface modified electrodes. Especially, in the case of using the surface sulfonated carbon electrodes, ultra-smooth surfaces whose roughness are 4nm (Ra) were obtained with 100% current efficiency. On the other hand, for the etching processes of cathode metal or semi-conductor, we used aminated gold electrodes, and etching rates of 0.2nm/s were obtained for the cathode AL. Applying these results, a new ultraprecision machining method in which using surface modified fine-particles dispersed in ultrapure water were proposed and tested. Surface aminated ultrafine particle whose diameters are 30nm were dispersed in ultrapure water and using dialysis the density of impurity of metal ions were lowered to ppb level. By using this new "electrolyte", we performed ultraclean electrochemical etching process of Si surfaces. The observed surface roughness for (001) and (111) surfaces were 0.1228nm (Ra) and 0.064nm (Ra), respectively. Finally, the present new electrochemical machining processes were applied to transcription of the geometry of electrodes to Cu, Al and W surfaces. In the case of using fine-particles whose diameters are 5mm, the transcriptions were successfully achieved.