We studied the generation of an ordered quantum dot array in an amorphous silica matrix by ion beam irradiation. In particular we investigated the influence of the irradiation process on the nucleation of Ge clusters, on the correlations in their positions and on the crystalline quality of Ge quantum dots formed after subsequent annealing. We have developed a method for the description of the intensity of grazing-incidence x-ray small angle scattering from irradiated multilayers, that enables a precise determination of the arrangement of quantum dots as well as their position correlation and size distribution. The analysis shows that the irradiation causes an ordering of Ge clusters along the irradiation direction, substantially improving the correlation in their positions. The observed phenomena are explained and simulated by a Monte-Carlo model based on the modification of local Ge density induced by ion tracks in the irradiated multilayers.

Fizika