Excitonic Quasimolecules in Nano Systems of Semiconductor and Dielectric Quantum Dots

The idea of superatom was fruitful for the development of nanophysics Superatom (quasiatomic nanoheterostructures) consists of a spherical quantum dot (QD) with radius a, the volume of that contains the semiconductor (or dielectric) material. QD is surrounded by dielectric(semiconductor) matrix. A hole is localized in the volume of QD, and the electron is localized over a spherical interface (QD-matrix). In this nanosystem the lowest electronic level is in matrix, and the lowest hole level is within volume of QD. A large shift of the valence band (700 meV) generates the localization of holes in the volume of QD. A significant shift of the conduction band (about 400 meV) is a potential barrier for electrons. 

The electrons moving in the matrix and do not penetrate in the volume of QD. Theenergy of the Coulomb interaction of electron with hole and the energy of thepolarization interaction of electron with interface (QDmatrix) form a potential well, in which the electron is localized over the surface of quantum dot. The certain orbitals, localized surrounding quantum dot correspond to electrons in superatom . During investigation of the optical characteristics of nanosystems with CdS, ZnSe, Al2O3 and Ge quantum dots in experimental papersit was found that the electron can be localized above the surface of the QD while the hole here moves in the volume of the QD. In Ref.