(a), (b) Schematic views of the QD arrangement in the QD lattice formed during self-assembled growth of a (Ge+SiO2)/SiO2 multilayer. The lattice formed has a three-dimensional rhombohedral structure with the  axis perpendicular to the sample surface. It is described by basis vectors . (c) STEM image showing ordering within a small domain. (d), (e) Measured and simulated GISAXS maps, respectively. The parameters of simulation are given in Table 2.