Figure 1.

Schematic diagram of the samples grown for obtaining vertical QD molecule structures. The first layer of nanostructures (QD1), is formed after depositing 1.2, 1.4, and 1.5 ML of InAs into GaAs nanoholes previously formed by droplet epitaxy. After the growth of 4-nm-thick GaAs barrier layer, a second layer of nanostructures (QD2) is formed on top of QD1 by a stress induced growth process when 0.9 ML of InAs is deposited

Alonso-Gonz├ílez et al. Nanoscale Research Letters 2010 5:1913-1916   doi:10.1007/s11671-010-9771-2