Acoustic phonons in semiconductor nanocrystals

The vibrational modes and low frequency Raman spectra of semiconductor InP nanocrystals embedded in different surrounding matrix have been calculated by using elastic continuum model. The frequency of vibrational modes increases with decrease in size. The surrounding matrix significantly affects the Raman lines representing acoustic modes and results into the line width broadening accompanied by damping of modes, which are explained based on the mismatch of acoustic parameters of matrix and nanocrystals. The mechanical coupling is found to play an important role in the damping mechanism of Raman frequencies.