Observation par topographie aux rayons X des configurations de dislocations développées a l'extrémité d'une fissure dans le silicium

Interaction of a dislocation with a crack tip: From stimulated emission to avalanche generation

“…This number is in agreement with the small activity noticed at secondary sources during creep experiments (less than 10 dislocations emitted per source) under comparable K Ia values (0.34-0.48l p b) [16]. Another indirect support to our model is given by the two-step loading procedure used to decrease the dislocation density in the plastic zone in order to facilitate the Burgers vector analysis [19].…”

“…The distribution of etch pits on the crystal's face orthogonal to the crack front was observed after plastic relaxation under creep conditions on {1 1 1} cleavages [16]. On the outer part of the plastic zone, a small number of welldefined rows of pits containing a few dozen dislocations are observed.…”

“…{1 1 0} cleavages propagating along a h1 1 0i direction were introduced by the wedge technique [16]. The crack length and the crack quality were checked by conventional X-ray topography.…”

Dislocation Nucleation and Multiplication at Crack Tips in Silicon

“…Tapered double-cantilever beam (DCB) samples of approximately 0.6 mm thickness were used [1,13]. Pre-cracking was achieved at room temperature using St. John's wedge technique.…”

“…0X5K IC . In ordinary a samples, static loading at K 0X3K IC is sufficient to create dislocations [2,13]. With highly perfect cracks, loadings during hours at K I approaching K IC failed to induce plastic deformation at the crack tip in the accessible temperature range, up to %1000 K. It was not possible to wait for longer times because a few hours anneal was observed to significantly relieve the crack tip stress field, probably by surface diffusion which causes crack tip blunting of the initially atomically sharp crack.…”