The structure of electrodeposited copper—III: The effect of current density and temperature on growth habit

Abstract

The effect of temperature and current density on the structure of copper deposits on copper single crystal surfaces near {100} has been studied. The electrolyte was a carbon-purified normal acid copper sulphate solution. At temperatures between 20 and 45°C, four basic structural types were observed; the current density at which any one type occurred increased with the electrolyte temperature. Overpotential measurements showed that each structural type was associated with a limited range of polarization. At overpotentials above approximately 100 mV the deposit was polycrystalline; below this it was coherent with the base, its habit being determined by the polarization. Below approximately 10 mV the surface was ridged, between 40 and 70 mV it was composed of platelets and between 70 and 100 mV it consisted of blocks and fine platelets. A gradual transition from ridges to platelets occurred at overpotentials between 10 and 40 mV. The structure was also found to be influenced by impurities in the electrolyte. A Tefel relationship between current density and overpotential was observed; the Tafel line changed slope as the current density was increased.