Electrodeposition of CuNiW alloys: thin films, nanostructured multilayers and nanowires

Electrodeposition operating conditions were determined for the deposition of copper-nickel-tungsten alloys and compositionally, multilayered deposits. Multilayered alloys with one layer rich in Cu and the other layer rich in NiW were fabricated as both thin films and nanowires. The electrolyte contained 0.6 M Na3C6H5O7, 0.2 M Na2WO4, 0.3 M NiSO4 and variable CuSO4 concentration at a pH of 8 adjusted with ammonium hydroxide at 70 +/- A 2 A degrees C. The deposit composition and current efficiency were characterized using rotating cylinder electrodes with and without a Hull configuration. Addition of Cu(II) to the electrolyte lowered the tungsten partial current density and hence the W wt% in the deposit. Thin film multilayered alloys, with a modulation in composition, were fabricated with pulse current deposition and conditions to selectively etch one layer was determined with a view towards fabricating nanotemplates. Nanowires with modulated composition were also demonstrated, electrodeposited into alumina nanoporous templates. However, the nanowire deposition was confounded by the formation of oxide during the modulation, and results herein recommend that the potential of the more noble step be more negative than -0.9 V versus SCE to avoid this situation, despite metallic alloy formation in unrecessed electrodes.