Nanoscale Metal/Metal Multilayers Electrodeposited from Ethaline

Abstract

Nanoscale metal/metal multilayer films electrodeposited from a single electrolyte under either potentiostatic or galvanostatic control have been widely studied. When the electrolyte contains two metal species it is possible to alternate between depositing the more noble component and an alloy of both simply by switching either the deposition potential or current density. Most work in this field has used aqueous electrolytes, but in some situations working with alternative solvents could offer advantages. Here we present results for Ni-Cu/Cu multilayers electrodeposited from an ethaline (1:2 choline chloride: ethylene glycol) electrolyte containing 1.2 M NiCl2 and 0.06 M CuCl2. The deposition potential was alternated between −0.45 V vs Ag/AgCl to deposit Cu and −1.2 V at which a Ni-rich Ni-Cu alloy was expected. Specular films consisting of multiple repeats with nominal thicknesses down to 5 nm Ni-Cu/ 1 nm Cu were obtained, and their multilayer structure was confirmed by X-ray diffraction. Average composition measurements for series of multilayers in which the thickness of one of the components was maintained constant provide further insight to the multilayer deposition process.