Epitaxy and oblique face development in nickel electrodeposits on a copper cube face, in relation to rate of deposition, deposit thickness, degree of stirring and bath temperature

Abstract

The epitaxial crystal growth and surface form of fcc nickel electrodeposits from the nickel sulphamate bath, on smooth copper {100} faces, are studied systematically by electron diffraction. Current densities up to 600 mA cm−2 and thicknesses up to 60 000 Å are investigated. The results with the bath at 20 and 50°C, and unstirred, show quantitatively the effects of the bath temperature, and additional results show the effects of vigorous stirring at 50°C.At 50°C two main isostructural regions of current density and thickness are distinguished, subdivided into five subregions where the surface or subsurface form is different. In the single-crystal region, negligible twinning due to lattice misfit occurs, in marked contrast to the strong twinning in Ni on Cu {110} and {111} using the same bath and conditions. The development of oblique faces is studied and a new region is found at high current density where their development is again very slow or absent. Above a certain current density, varying with deposit thickness, co-deposition of Ni(OH)2 occurs, leading to twinning and random Ni crystals.

The structure and crystal growth of nickel electrodeposits from a sulphamate bath on polished polycrystalline copper, in relation to thickness, rate of deposition, temperature and stirring

“…The present results show that Ni(OH)2 is co-deposited at cd at which the current efficiency falls appreciably below loo%, and hydrogen is evolved at the cathode. This agrees with the views of previous authors (see Verma and Wilman 1971) that it is due to removal of hydrogen ions by deposition and Hz evolution at the cathode, resulting in the solution near the cathode increasing in pH (becoming more alkaline), leading to precipitation of hydroxide on the cathode. Germer (1938) obtained electron diffraction patterns from crystalline Ni(0H)z formed by reaction of a nickel alloy (German silver) with water, and found it had the normal hexagonal structure with a=3*117A and c=4,595A.…”

“…This form is similar to that first shown for the onset of twinning by Setty and Wilman (1955) in the case of silver deposits from the cyanide bath on electropolished silver single-crystal faces, and subsequently in this laboratory by Cusminsky and Wilman (to be published) and Cusminsky (1965) for copper deposits from a 0.5M CuS04-0.5M HzS04 bath on smooth electropolished copper crystal faces, and by Sundaram (1966) for silver deposits from O.5N AgN03 on electropolished silver crystal faces. This form was also obtained in our nickel electrodeposits from this sulphamate bath on electropolished copper single-crystal faces (Verma and Wilman 1971). Matthews et al (1961) pointed out that this form is roughly similar to that which would correspond to a particular stage of cathode surface roughness, and therefore to a particular effective local cd on the cathode projections (larger than the mean cd), at which most of the deposition was occurring.…”

“…The effect caused by rotating the cathode is similar to that of stirring, namely to reduce the thickness of the diffusion layer, and it has been discussed theoretically by Levich, Agar and Vetter (see Verma and Wilman 1971). Some observations by electron diffraction were made in this laboratory by Yang (1948) on the effect of rotating the cathode at several thousand rpm.…”

“…Although empirical expressions have been given by Levich (1942Levich ( , 1944Levich ( , 1962, Agar (1947) and Vetter (1967) (for references see Verma and Wilman 1971) for the effect of forced convection by a rotating stirrer on the thickness of the diffusion layer, the effective increase in the rate of supply of cations to the actual regions of deposition on the cathode is not easy to estimate. The above estimate from observations of the boundaries of the isostructural regions is thus particularly valuable and has the advantage of directness.…”

Potential Modulated Multilayer Deposition of Multisegment Cu/Ni Nanowires with Tunable Magnetic Properties

“…The fcc stacking twin structure can be clearly distinguished in the inset. We note that strong twinning has been reported for nickel films deposited from sulfamate solution on Cu (110) and Cu (111) 7 High-resolution TEM image of a Ni segment in a 100 nm diameter multilayer nanowire with 10 nm Ni layers and 5 nm Cu layers showing a high density of twins.…”