Fracture toughness of silicon in nanometer-scale singular stress field

• We successfully introduced a short crack into a single-crystal Si micro-specimen.
• The singular stress field size in micro-specimens with a crack is 23–57.9 nm.
• The crack propagation behavior was directly observed by means of a TEM.
• The KIC in a nanometer-scale is equivalent to that of the bulk counterpart.
• The fracture toughness in a nanometer-scale is independent of the size.

The purpose of this study is to examine the size effect of a singular stress field on the fracture toughness at the nanometer scale. The cracking behavior is investigated using small single-crystal silicon specimens with different precrack lengths where the size of the singular stress field, ΛK, near the crack tip is 23–58 nm. The fracture toughness, KIC, is approximately 1 MPam1/2 in all of the specimens, which is in good agreement with that of the macroscale (bulk) counterpart. This clearly indicates that the fracture toughness is independent of size while it was reported that the tensile strength without a crack showed strong dependence at the nanometer scale.