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 [quantum dots (QDs)] we re 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-contr ast modes. Complementary results from wider sample areas were obtained by m eans of photoluminescence spectroscopy. In one of the samples analyzed, a f ractional monolayer of MnSe was deposited immediately before the CdSe depos ition. A second structure grown underidentical conditions, but without the MnSe fractional monolayer, was also analyzed. This comparison provides dire ct 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 s tructure, we observed the co-existence of highly strained quasi-2D QDs and CdSe rich aggregates with compositional modulations on certain crystallogra phic planes in close proximity.