The purpose of this work is to study the electrocrystallization behavior of the copper deposit on pure titanium substrate. The electroplating was conducted at 0.7 A/cm 2 , 65°C in cupric sulfate-sulfuric acid bath with various chloride additions ͑45-350 ppm͒. Initial growth morphology and microstructure of the deposit were examined with a field-emission scanning electron microscope ͑FESEM͒ and a high-resolution transmission electron microscope integrated with an energy-dispersive X-ray spectrometer. Results of cathodic polarization and galvanostatic plating experiments show that the increasing concentration of chloride ions in the plating bath would significantly increase the cathodic potential. This cathodic potential increase was found to be induced by the presence of CuCl precipitates on the cathodic surface as well as on the copper cluster formed during the electrocrystallization process. At the initial plating stage, both copper and hexagonal-shaped CuCl precipitates were produced simultaneously. Eventually, the pyramid-shaped CuCl precipitates were observed, which consisted of many parallel hexagonal planes stemming from a screw dislocation. The polarization effect of CuCl precipitate on the Ti substrate was further confirmed and clarified. Through measurement of the electrode response and investigation of the deposit using FESEM, it was observed that under identical electroplating conditions, much less CuCl forms on a copper substrate in the initial stages than on a titanium substrate, leading to lower polarization.
The cyclic voltammetry stripping (CVs) behavior of the tin-doped indium oxide (ITO) on SiO2 in 0.3M HCl is reported. The CVs result showed an obvious reduction-current peak that occurred during the first cathodic potential scanning. Smaller reduction current and more negative potential of the reduction-current peak were also observed for the ITO that was annealed at 500 °C. The result was attributed to the replenished oxygen-deficient site and the oxygen anion density is decreased in the ITO. The present study has proved that CVs is a useful method to differentiate the carrier concentration in ITO film controlled by different pretreatments. Many spherical In-Sn particles were formed on the ITO when the reduction current took place. During precipitation of these spherical particles, the grain boundaries of the ITO were dissolved and the ITO surface nearby the grain boundaries offered a preferred nucleation site for the formation of these spherical In-Sn particles. Based on the microstructure observed and the result derived from the short potential range scanning, the formation mechanism of the spherical particle is proposed.
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