  Mulheran and Blackman have provided a simple and clear explanation of the
scale invariance of the island size distribution at the early stage of film
growth [Phil. Mag. Lett. 72, 55 (1995)]. Their theory is centered on the
concept of capture zone properly identified by Voronoi cell. Here we
substantiate experimentally their theory by studying the scale invariance of
InAs quantum dots (QDs) forming on GaAs(001) substrate. In particular, we show
that the volume distributions of QDs well overlap the corrisponding
experimental distributions of the Voronoi-cell areas. The interplay between the
experimental data and the numerical simulations allowed us to determine the
spatial correlation length among QDs.
