Flow-induced composition modulated NiFe thin films with nanometer-scale wavelengths

Described are results showing that an oscillating flow-field can induce spatially periodic composition variations in electrodeposited NiFe thin films. Flow-induced NiFe composition modulated alloys (CMAs) were deposited on the disk of a rotating ring-disk electrode (RRDE) by oscillating the RRDE rotation rate. Deposit composition profiles were analyzed using potentiostatic stripping voltammetry, which allowed the relationship between the alloy deposition parameters and CMA structure to be investigated. Results show that the composition modulation wavelength is inversely proportional to the flow oscillation frequency. CMAs made at disk oscillation frequencies greater than 100 mHz had modulation wavelengths less than 20 nm when plated galvanostatically at -10 mA/cm(2). Scanning tunneling microscopy images indicate that plating at different current densities leads to deposit growth front morphologies that influence the ability to resolve short wavelength compositional structure. The limitations of stripping voltammetry for composition depth profiling, and the implications of the results for the industrial plating of Permalloy in paddle cells, are discussed.