Synchrotron X-ray topographic observations were performed in situ on initially dislocation-free single crystals which were deformed in creep at between 975 and 1075K, using tensile stresses of 22 or 44MPa. It was observed that the first dislocations, which were created at Vickers micro-indentations or residual surface damage, did not develop in a strictly planar manner. Prismatic half-loops, which glided on two {111} planes simultaneously, were commonly observed. Cross-slip events appeared to be quite frequent; in the bulk as well as at free surfaces. Groups of similar dislocations soon exhibited irregular shapes, with cusps and trailing dipoles. This was taken to be an indication that they developed jogs during their motion. Several configurations of dislocation sources, which were formed from mobile dislocations, were observed. The formation of new sources usually involved cross-slip. The jogs which were formed by forest-cutting seemed to be important. The efficiency of the sources was strongly limited by a lack of stability of the cross-slipped segments, which acted as poles for the Frank-Read mechanism.

Dislocation Multiplication in Silicon at the Onset of Plasticity Observed by in situ Synchrotron X-Ray Topography. A.Jacques, F.Vallino, F.Serbena, A.George: Journal of Physics - Condensed Matter, 2000, 12[49], 10045-58