Self-ordered CdSe quantum dots in ZnSe and (Zn,Mn)Se matrices assessed by Transmission Electron Microscopy and Photoluminescence Spectroscopy

Single and multilayer sheets of self-assembled CdSe (QDs) were grown by means of molecular beam epitaxy in both ZnSe and (Zn0.9Mn0.1)Se matrices. Both types of structures were assessed by means of transmission electron microscopy in the scanning, high-resolution, and diffraction-contrast modes. Complementary results from wider sample areas were obtained by means of photoluminescence spectroscopy. In one of the samples analyzed, a fractional monolayer of MnSe was deposited immediately before the CdSe deposition. A second structure grown under identical conditions, but without the MnSe fractional monolayer was also analyzed. This comparison provides direct evidence for an enhanced size and shape homogeneity of 3D QDs caused by the presence of a tiny amount of MnSe at the interface. In the multilayer structure, we observed the co-existence of highly strained quasi-2D QDs and CdSe rich aggregates with compositional modulations on certain crystallographic planes in close proximity.