Influence of depth on the amount of nucleating QDs per holes. In (a), the fraction of the number of QDs per hole nucleating inside a hole is given. With increasing etching duration and therefore depth, the number of QDs per hole decreases. Also, the broadening of the distribution and therefore the standard deviation of the number of QDs per hole is smaller. The influence of the volume of the hole on the number of QDs nucleating per hole is given (b). Both images show the superior properties of deeper holes. In (c), an amplitude picture of an AFM scan is given. It can be seen that although the diameter is quite large with a size of 150.3±4.1 nm and an aspect ratio of 1.164±0.071 is also not perfect, the number of QDs can be decreased to one to two QDs per hole. Optimizing these parameters should therefore lead to a number of QDs closer to one.
Mayer et al. Nanoscale Research Letters 2013 8:504 doi:10.1186/1556-276X-8-504