TRANSVERSE ACOUSTIC PHONONS IN AMORPHOUS-SILICON

The evolution of the broad transverse-acoustic phonon density-of-states peak at approximately 150 cm-1 in amorphous silicon produced by introducing increasing damage to a crystal is investigated. By comparison to the phonon density of states as derived from second-order Raman scattering on the same samples, and to a theoretical calculation of these branches, it is concluded that the L-branch ([111]-direction) is most susceptible to the loss in periodicity. Further, it is found that at low damage levels phonons with longer wavelengths contribute more to the phonon density of states than zone-boundary vibrations.