It was shown by energy- and time-resolved phonon spectroscopy with superconducting tunneling junctions that acoustic phonon scattering depended upon the size of O precipitates in the annealed Czochralski Si crystals. After heat treatment at about 1050C, a series of rather narrow scattering resonances was found that shifted under stress. They were suggested to be due to electronic excitations of acceptor-like states related to O aggregation.

Phonon Scattering of Oxygen-Related Defects in Annealed Silicon Crystals. F.Zeller, K.Lassmann, W.Eisenmenger: Physica B, 2002, 316-317, 417-20