First-principles calculations of vibrational spectra of CdSe/CdS superlattices

The vibrational spectra of CdSe/CdS superlattices (SLs) with different layer thicknesses are calculated from first principles within the density functional theory. It is shown that, along folded acoustic and confined optical modes, a number modes appear in SLs. In structures minimum thickness one layers, microscopic interface similar to local gap crystals appear. An analysis projections eigenvectors SLs onto orthonormal basis normal binary compounds enables establish details formation these and, particular, determine degree intermixing modes. A comparison frequencies nanoplatelets separate influence size quantization surface relaxation on nanoplatelets. Keywords: phonon spectra, semiconductor superlattices, cadmium selenide, sulfide, nanostructures.