Electrochemical characterization of copper deposited on plasma and thermally modified titanium surfaces

Thin oxide films were grown at temperatures from 373 to 1073 K in plasma and in air on commercially pure titanium substrates. It was determined that the color, thickness, composition, phase, and polarization behavior in a copper electrolyte varied with operating conditions: temperature, oxygen partial pressure, and plasma composition. High-temperature and high oxygen partial pressure plasma produced a thick oxide film. The surface film structure transformed from TiO₂ (anatase) to TiO₂ (rutile) at a temperature of 600 °C. A lower oxide of the form Ti _n O_2n−1, such as Ti₂O₃ (which may be porous) or possibly Ti₃O₅, was formed on a thermally treated sample (400 °C, 80 mtorr O₂, 3 hours). This sample exhibited the lowest potential for copper nucleation and gave a very uniform, smooth, and hole-free copper foil.