Size-dependent fracture properties of cracked silicon nanofilms

We evaluate the applicability of the critical energy release rate as a crack propagation criterion with a focus on the effect of the material size. Cracked silicon nanofilms of various thicknesses under uniaxial tensile loading are simulated to examine the influence of film thickness on the critical energy release rate. Tensile stress–strain curves in addition to the atomic configurations corresponding to different strain levels are presented to elucidate the deformation mechanism. The cracked silicon nanofilms subjected to mode I loading deform nonlinearly to some extent. The critical energy release rates are calculated by three approaches: a molecular statics simulation, the Griffith criterion, and linear elastic fracture mechanics. Results obtained from these three methods are compared with each other and the differences between them are discussed. The critical energy release rate may be capable of predicting crack propagation when the silicon nanofilms are thicker than approximately 18 nm.