Epitaxy of nickel electrodeposits on a copper (110) face, from a sulphamate bath, in relation to rate of deposition, deposit thickness, degree of stirring, and bath temperature

Abstract

Grazing-incidence electron diffraction at 50–60 kV shows the surface structure of smooth electropolished Cu (110) faces and of the epitaxial Ni deposits on them from the bath: Ni(SO₃· NH₂)₂· 4H₂O 350 g/l., NiCl₂· 6H₂O 5g/l., H₃BO₃ 35 g/l.

The Ni deposits were all f.c.c. The effects of c.d. (up to 600 mA/cm²), thickness (100–60 000 Å), temperature (50 and 20°C), and vigorous stirring, are shown in detail. The effects of codeposition of Ni(OH)₂ at high c.d. are also shown.

Special points of interest are: (1) at 50°C although {111} twinning of the “parallel” epitaxial Ni was strong near the interface (100–200 Å Ni deposits) at up to ∼150 mA/cm², it was weaker at 200 and absent at 300–600 mA/cm²(at least up to thousands of Å thickness), and this is similar to our results for Ni on (100) and (111) Cu; (2) at up to ∼150 mA/cm² at 50°C with unstirred bath the strongly twinned Ni at up to 1000 Å thickness showed no “directed disorientation” though accompanied by an extremely small trace of widely disoriented (random?) Ni, possibly associated with the epitaxial misfit and contacting crystal nuclei; (3) at 10 000 Å or more, at up to ∼150 mA/cm² at 50°C with unstirred bath, additional weak arcs showed a small amount of {100} Ni, and at 30 000–60 000 Å these arcs became strong and showed a {100} Ni orientation but limited to azimuths associated with those of the {111} twins of the “parallel” Ni, arising from the twins by a “directed disorientation”(a range of rotation round the horizontal [10] Ni direction, presumably due to contacts between the twins, as they grow, with misfit stresses and strains at their interface), followed by cube face development leading to preferred growth of crystals in {100} orientation.