FLOW-INDUCED COMPOSITION MODULATED NIFE THIN-FILMS WITH NANOMETER-SCALE WAVELENGTHS

Described are results showing that an oscillating flow-field can induc e spatially periodic composition variations in electrodeposited NiFe t hin films. Flow-induced NiFe composition modulated alloys (CMAs) were deposited on the disk of a rotating ring-disk electrode (RRDE) by osci llating the RRDE rotation rate. Deposit composition profiles were anal yzed using potentiostatic stripping voltammetry, which allowed the rel ationship between the alloy deposition parameters and CMA structure to be investigated. Results show that the composition modulation wavelen gth is inversely proportional to the flow oscillation frequency. CMAs made at disk oscillation frequencies greater than 100 mHz had modulati on 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 de pth profiling, and the implications of the results for the industrial plating of Permalloy in paddle cells, are discussed.