In a Brillouin scattering study of ZnSe-ZnSe1-xSx strained-layer super
lattices' film, we have observed large increases for the longitudinal
elastic constants C-11, and significant decreases for shear elastic co
nstants C-44, than the predicted value seems to be only relevant to th
e existence of imperfect interfaces. In order to explain these results
, we use an interface layer (I layer) model. The structure (-AIBIAIBI-
) of superlattices has been both observed in transmission-electron mic
roscopy (TEM) observations and Raman spectra.