Surface effect on the quantum size energy levels in semiconductor nanocrystals

Friday, February 13, 2009 - 2:30pm - 3:00pm
Lind 305
Alexander Efros (Naval Research Laboratory)
We study the effect of the surface on the electron and hole energy level structure in spherical semiconductor nanocrystals within 8 band effective mass approximation. The surface properties are modelled by the General Boundary Conditions that allow us to exclude spurious and wing contributions to the eight band envelope function. The boundary conditions contain a surface parameter that is independent of the energy of the electronic states and should be considered as additional to the set of effective mass parameters describing the bulk semiconductor. We have shown that this parameter: (i) effects strongly the size dependence of the electron and hole quantum size energy levels, (ii) changes the symmetry of the lowest energy levels in the valence band, (iii) leads to the existence of surface localized states with energies within the forbidden gap, (iv) induces the spin-orbit splitting of the conduction band states, and (v) causes additional magnetic moment of the electrons.