Dislocation networks in twisted silicon

In order to introduce an excess screw dislocation density into Si single crystals, cylindrically shaped specimens were twisted around a [111]-axis at 1290 K to different twist angles. A subsequent annealing treatment (various durations) followed at 1420 K. The dislocation structures were examined by transmission electron microscopy (TEM); in addition, high-voltage TEM and stereographic methods were applied. The optimum experimental conditions were given by a twist angle of 240° cm−1 and 4 hours anneal. An average screw dislocation density of 2 × 109 cm−2 was then obtained, which is identical to a fraction of 65% of the total dislocation content.