Ay. Belov et al., Dissociation of screw dislocations in (001) low-angle twist boundaries: a source of the 30 degrees partial dislocations in silicon, PHIL MAG L, 79(8), 1999, pp. 531-538
The first experimental evidence for dissociation of grain boundary screw di
slocations is presented for (001) low-angle twist boundaries in silicon. Us
ing a combination of high-resolution electron microscopy and the weak-beam
technique of transmission electron microscopy, it is found that the grain-b
oundary screw dislocations (b =1/2[110]) can dissociate in the (111) plane
into 30" partials, forming an intrinsic stacking fault, as do lattice screw
dislocations of the glide set. On dissociation one partial dislocation sta
nds off the grain-boundary plane. Some segments of the grain-boundary screw
dislocations, however, may remain undissociated. An atomic model for the u
ndissociated screw dislocation core, as well as a mechanism of its transfor
mation into cores of individual 30 degrees partials upon dissociation, are
proposed on the basis of classical molecular dynamics simulations with an e
mpirical interatomic potential. The model enables an understanding of the r
esults of electron microscopy investigations.