抄録
Cathodic current-potential curves were measured for copper electrode in copper pyrophosphate solutions at a pH of 8.5. The deposited copper was examined by means of electron probe microanalysis, scanning electron microscopy and X-ray diffraction techiniques. The cathodic polarization characteristics revealed. that the amount of pyrophosphate ion adsorption decreases with increasing cathodic polarination and it becomes almost zero beyond the critical potential of Eb (ca. -0.75V vs. SCE). As could be expected, the phosphorus content in the deposit was relatively high (0.07-0.05%) in the potential region I which is less negative than Eb, and it was low (-0.02%) in the region II which is more negative than Eb. Smooth, semibright deposits were always obtained when the potential was in the region I and current was larger than about 5mA/cm2. The smooth deposit exhibited random orientation and main peaks were of (111), (200), (220) and (311). On the contrary, rough deposits obtained in the region II showed strong preferred (220) orientation and it is consistent with the preferred orientation theory. The deposition of a semibright layer in the region I is explained as being due to the pyrophosphate adsorption which prevents the surface migration of ad-atoms (or ad-ions) and hence the preferred orientation of crystals.
