Dependence on diameter and growth direction of apparent strain to failure of Si nanowires

Previous studies of the mechanical properties of Si nanowires have not shown the size-dependent strengths that are expected for this prototypical brittle material. A potential source of the ambiguity in the literature is the development of tensile stresses during the large (nonlinear) deflections that were present during the flexure tests. In this work we show that size-dependent strengths can be observed in Si nanowires when they are evaluated using uniaxial tension loading conditions. Si nanowires with diameters ranging from 268 to 840 nm were fabricated using the vapor-liquid-solid method and were strained to failure in vacuum using a micromachined load frame. The smallest nanowires were the strongest but the magnitude of the size effect suggests that the flaw populations in Si nanowires are orientation-dependent. © 2011 American Institute of Physics.