科研之友
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摘要
This study investigates the crystallographic orientations most widely known to exhibit fractures in silicon, such as those on the (111) plane cracks travelling along the [(2) over bar 11] direction (Si(111) [211] cracks). The (111) crack plane is believed to be the most stable fracture plane. However, fracture instabilities caused by brittle crack jumps remain on (111) the crack plane in a discontinuous manner. In this study, molecular dynamics simulations were performed to investigate the atomistic-level studies of fracture properties under a uniaxial tensile load (mode I load) in the (111) [(2) over bar 11] Si system. Our simulation results suggest that the formation of untypical-membered Si atomic rings in the vicinity of the crack tip, which can be induced by atomic stress near the crack tip, has an important role in the behavior of crack propagation instabilities. The presence of untypical-membered Si atomic rings acts as a self-protecting mechanism that contribute in maintaining the crack on the (111) fracture plane. Notably, our simulations also presented that the situation when a seven-Si atomic ring moves away from the crack tip associated with a sudden jump of crack speed can be regarded as the origin of the peculiar speed advancement behavior of the Si(111) [(2) over bar 11] systems. Moreover, several of our simulation results are in agreement with related experimental measurements.
