Abstract
The structural evolution of helium related extended defects in silicon, formed after intermediate dose helium implantation and annealing has been investigated. It is found that the highest helium concentration (annealing at 300ºC) is associated to clusters of bubbles arranged in a platelet-like morphology. At 500ºC the helium concentration markedly decreases and clusters of cavities formed by a central, large cavity surrounded by small cavities (planetary like structures) are detected. The thermal treatment at 900ºC accomplishes the complete helium effusion from the sample leaving behind empty cavities i.e. voids.