Phonon modes in spherical GaAs quantum dots (QDs) embedded in spherical AlA
s shells with up to 11 855 atoms (about 8.0 nm in diameter) are calculated
by using a valence force field model. All the vibration frequencies and vib
ration amplitudes of these shell QDs are calculated directly from the latti
ce dynamic matrix by employing the projection operators of the irreducible
representations of the group theory. The effects of the size of GaAs cores
and the thickness of AlAs shells on the phonon modes are investigated. The
quantum confinement effects of both the vibration frequencies and vibration
strengths are investigated. The microscopic interface modes, which can onl
y be revealed by the microscopic model, are identified and discussed. (C) 2
001 American Institute of Physics.