INFLUENCE OF THE DEGREE OF DISORDER OF AMORPHOUS SOLIDS ON THE INTENSITY OF LIGHT-SCATTERING BY ACOUSTIC PHONONS

It is observed experimentally that in the low-frequency Raman light sc attering spectrum of amorphous porous silicon the boson peak situated in the acoustic range is more sensitive to the structural order than t he optical mode presently used to determine the degree of disorder. It is shown that this is because, unlike the coefficient of interaction with optical vibrations, the coefficient of interaction between light and acoustic vibrations contains an additional factor, the square of t he reciprocal correlation length of the vibrational excitations, i.e., the intensity of light scattering by acoustic phonons has an addition al dependence on the degree of disorder. (C) 1998 American Institute o f Physics.