Mechanical properties of columnar submicron cobalt structures with various cross-sectional geometries

Submicron-scale columnar cobalt structures with three different cross-sectional geometries – solid cylinders, x-shaped pillars and keyhole-shaped pillars – were characterized by uniaxial compression tests. All electroplated specimens possess a hybrid polycrystalline–nanocrystalline microstructure. Results of uniaxial compression revealed that the average mechanical strengths of submicron cobalt specimens are statistically indistinguishable, regardless of cross-sectional geometry. This surprising result is in contrast with previous studies of solid cylindrical pillars, where the mechanical strength shows a dependence on specimen size.