An Ex-Situ Study on Epitaxial Growth of Nickel on Copper Substrate in Electrodeposition

Abstract

An ex-situ method was used to study the anisotropy of the epitaxial growth of electrodeposited nickel on polycrystalline copper substrate. The substrate grain orientation was characterized by electron backscatter diffraction (EBSD) technique prior to the electrodeposition. Nickel films of approximately 1 μm thick were then deposited onto the polished substrates in a sulfamate bath at current densities 2 to 250 mA/cm2. The orientation of the Ni film in the prior-analyzed area was characterized again by EBSD to reveal the orientation relationship between each deposit/substrate pair. EBSD analysis was also carried out for thick deposit from a transverse direction to clarify the growth behavior and microstructural evolution on grains of different orientations. Results indicated that epitaxial growth was allowed solely on grains having an orientation of <100>//ND at 2 mA/cm2. On the contrary, nickel deposits grew epitaxially on all grains no matter the orientation as the current density was in a range of 10-100 A/cm2. However, the surfaces of the non-(100) oriented epilayers became rough with increasing thickness and finally they were covered by fine nuclei formed via a twin-mediated nucleation process.