Atomic structure and core composition of partial dislocations and dislocation fronts in β-SiC by high-resolution transmission electron microscopy

We study the atomic structure of single dislocations and of dislocation fronts in recrystallized β-SIC, using high-resolution transmission electron microscopy images of edge-on defects. The Burgers vectors of the defects are determined on the images. The structural units (SUs) and the core composition of the defects are obtained by an analysis of the image contrast. Single 30° Si(glissile) or 30° C(glissile) are emitted during recrystallization of β-SiC at T > 1900°C. Their SU verifies the model proposed for elementary and compound semiconductors. The dislocation fronts gliding under thermal or thermodynamic stresses consist of a pile-up of different Shockley partials. The dislocation triplets consist of one 90° C(glissile) and two 30° Si(glissile) or vice versa. The core compositions of the 90° and of the 30° partial dislocations are also different in the fronts of two dislocations characterized by a Burgers vector equal to 1/12 [Left Angle Bracket] 112 [Right Angle Bracket] ac. The SUs of the dislocation fronts are due to a reconstruction of the SUs characteristic of the 90° and of the 30° SUs. The probability of formation of the dislocation fronts is independent of the core composition of the partials.