Glide Band Formation in Silicon

Abstract

Birfringence and etch pit studies of the initial stages of plastic flow in octagonal‐shaped silicon crystals oriented for single slip and compressed at low strain rates in the temperature range 750–800 °C show characteristics quite similar to that found for avalanche behavior and ``Luders‐band'' type flow in alkali‐halide crystals. The narrow glide bands taper to a single plane at opposite ends and the dislocation morphology, as revealed by their phase retardation birefringencecharacteristics, is in the form of large concentric loops on neighboring planes with staggered sources in the central region of the band. Calculations show that the stress field from dislocation arrays enhances the formation of neighboring arrays by double cross slip and multiplication, and show how different kinds of defects can form. The enhanced shear stress at the cross‐slipped segment is significantly greater if the initial source operates on the surface. The effects of partialized dislocations and various dynamic effects which affect the begining and cessation of glide band formation and broadening are shown to be consistent with avalanche behavior.