Indentation of single-crystal silicon nanolines: Buckling and contact friction at nanoscalesa)

High-quality single-crystal silicon nanolines (SiNLs) with a 24 nm linewidth and a height/width aspect ratio of 15 were fabricated. The mechanical properties of the SiNLs were characterized by nanoindentation tests with an atomic force microscope. The indentation load-displacement curves showed an instability with large displacement bursts at a critical load ranging from 9 to 30 μN. This phenomenon was attributed to a transition of the buckling mode of the SiNLs under indentation, which occurred preceding the final fracture of the nanolines. The mechanics of SiNLs under indentation was analyzed by finite element simulations, which revealed two different buckling modes depending on the contact friction at the nanoscale.