Effect of surface morphology on the fracture strength of silicon nanobeams

The effect of nanoscale surface morphology on the fracture strength of 190-nm-thick, doubly clamped Si beams was measured experimentally. The surface morphology was controlled through aqueous etching and characterized by atomic force microscopy. The beams fractured along the primary cleavage planes, {111}. Fracture strength was extracted using finite element simulations of the experiment. Nanobeams etched with relatively smooth morphologies (0.4 nm rms) were able to sustain a tensile stress of 15.8 GPa, close to theoretical strengths predicted by previous atomistic calculations. In contrast, nanobeams decorated with nanometer-high step bunches (1.5 nm rms) had a 20% lower fracture strength, 12.8 GPa, suggesting that careful attention to processing is necessary for maximum strength. (c) 2006 American Institute of Physics.