Alternating current etching of aluminum in chloride solution produces an etched layer composed of an ant-like porous structure that is used as electrodes in electrolytic capacitors for a large specific surface area. The effect of frequency and etchant on the layer formation was examined by means of capacitance measurement of etched foil, scanning electron microscopy and Auger electron spectroscopy. The structure of the layer can be characterized by etched depth, etch products amount and its distribution and cubic etch cell size. The amount of etch products was greater at lower etchant temperature, at higher frequency of current, and at the subsurface than at the bottom of a layer. Changes in the typical etch cell size with frequency to the -0.63th power was discussed in terms of current efficiency.
The ratio of drive frequency f to capacitance C of the barrier layer on electrodes was investigated to generate a glow-like barrier discharge in air at atmospheric pressure. The uniformity of the discharge was estimated by observing the optical emission from the discharge through a transparent electrode and a glass plate used as the barrier layer. The impedance of the barrier layer 1/(2πfC) was kept at 12.3kΩ and the drive frequency f was varied from 33.3kHz to 100kHz. Air and nitrogen were both used as the discharge gas. The discharge contained bright spots generated by self-organization. The distribution and diameter of the bright spots were affected by f/C and the species of discharge gas used. The lager f/C was chosen, the more homogeneous the discharge that appeared when nitrogen served as the discharge gas. In contrast, the optimum value of the f/C that allowd homogeneous discharge occurred when air was used. It seems that the bright spots appear more readily when either the discharge cycle is shorter than the lifetime of the active species or when the effects of discharge current regulation by the barrier layer lessen.
Cu foils for circuit board manufacturing in microelectronics are produced using electrodeposition method from copper (II) sulfate aqueous solutions containing various additives. Such additives as gelatine and chloride ion are added to form the deposit surface having a periodic roughness. However, the composition in the electrodeposition bath and electrolytic current are the product of empirical research and the actions of these additives are still far from being fully understood. In this study, the effects of gelatine and chloride ion on copper electrodeposition were investigated. The surface morphology and crystal orientation of the deposits were examined by SEM and XRD. The copper deposits from the electrolyte containing gelatine and chloride ion grew in the ‹110› direction and columnar structures were formed. Moreover, on the deposits surface, pyramidal shapes were observed. The sharpness of the pyramidal shape increased with an increase of the concentration of gelatine and chloride ion and an excessive addition of gelatine caused the decrease of the sharpness. These results suggest that chloride ion is adsorbed preferentially on the (220) plane and promotes the electrodeposition of copper on the plane, on the other hand, gelatine is adsorbed preferentially on the (111) plane and suppresses the electrodeposition on the plane.
Adsorption behavior of a polyphosphate-zinc as corrosion inhibitor was examined on a gold electrode. While under a constant cathodic potential, the inhibitor's behavior was investigated in-situ by means of an electrochemical quartz crystal microbalance technique and surface observation using atomic force microscopy (AFM). The electrode potential (E), the concentration of dissolved oxygen (DO), the amount of polyphosphate-zinc inhibitor, and the solution pH affected on the cathodic current density and the change in the mass of the electrode. The amount of adsorbed inhibitor increased with an increase in the inhibitor concentration and concentration of dissolved oxygen, as well as with a decrease in the electrode potential at pHs7 and 8. The adsorbed amount reached 9μgcm-2 within 1200s at E=-0.75V with respect to a Ag/AgCl (sat. KCl) reference electrode in a 0.1moldm-3 Na2SO4 solution containing sodium hexametaphosphate (68ppm PO4), zinc chloride (20ppm Zn), and 20ppm poly-acrylic acid at pH7, DO=7.8ppm and 298K. The adsorpant was found to be several nanometers thickness according to AFM observation
On the photoelectrochemical cell consisiting of the TiO2 photoanode prepared from thermal oxidation of titanium and the graphite cathode in 100mL of the aqueous solution of 10μmol/L Pb(NO3)2-0.1mol/L HNO3, the UV irradiation led to the performance of the elimination of Pb2+ ions by the photoanodic deposition of PbO2 on the TiO2 surface.