Kink Deformation in Ni-Co-Cu/Cu Multilayered Films Fabricated by Electrodeposition

To investigate the effect of component layer thickness on kink-like deformation of multilayered structure, Ni-CoCu/Cu films having various layer thicknesses were compressed along film plane. The Ni-Co-Cu/Cu multilayered films were fabricated by the special electrodeposition technique at which a rectangle potential wave form was applied to a copper substrate immersed in electrolyte containing Ni2+, Co2+ and Cu2+ ions. Total thickness of the films was approximately 3 μm and individual layer thicknesses ranged from 100 nm to 1 μm. The films were electrodeposited on annealed copper substrates of 3 mm thickness. Then, the substrates were shaped to 3×3×6 mm3 dimension, where a film was coated on one of four longitudinal planes. Compression tests were conducted on the substrates until 20% strain, and thus the films shrank to in-plane direction with substrate. After the compression tests, we observed film surfaces with SEM and found that band-like structures were developed. The band-like structures arranged along transverse direction. From cross sectional observations, the band-like structures had moderate kink shapes expanding normal to surface. Shape of the band-like structure was quantified by surface SEM observation: the longitudinal length and the thickness corresponding to short axis length of each band were measured. The thicknesses of the band-like structure decreased with decreasing component layer thickness, while the longitudinal lengths were almost independent of the layer thickness.