Size effects on deformation mechanism of nanopillars by FIB-CVD using double-cantilever testing

Nanopillars and nanocoils fabricated by chemical vapor deposition using a focused ion beam were used to estimate bending and torsional rigidities under infinitesimal deformation and to investigate nonlinear large deformation behaviors. For the pillars, we performed bending tests using a unique double-cantilever specimen, which was made by joining two pillars together using focused electron beam deposition in a scanning electron microscope. The reproducible load–deflection curves, which were not severely disturbed by the ambiguous chuck condition of the specimens, indicated that the pillar deformation resistance decreased after the linear response (called softening), and it was dependent on the pillar diameter and the ratio of diameter to length. However, all pillars became extremely hardened at large deformation. At diameters of less than 300 nm, and at diameter/length ratios of over 10−2, this nanopillar size effect (characterized as softening) was consistently observed.