Circular and Hexagonal Stacking Faults in Bulk Silicon Crystals

Circular and hexagonal defects were formed in bulk silicon crystals by annealing and slow cooling. Some of these circular defects were unusual in possessing spoke‐like radial lines in 〈110〉 directions. By use of the rule that the Burgers vector is invariant against displacement of the Burgers circuit through good crystal regions, the radial lines are shown to have zero net Burgers vector and thus are probably dislocation dipoles. A mechanism is presented that accounts for the observed defects in terms of the formation of Frank sessile loops and half‐loops. The principal significance of this interpretation is that when the circular defects containing radial lines appear, precipitates are present in the material.