The effects of defects upon coherent phonons in ion-implanted Bi, graphite and GaAs were studied. The ultra-fast dynamics of coherent phonons in the time-domain were investigated by means of fs pump–probe reflectivity techniques. In Bi, the de-phasing rate of the A1g phonon increased linearly with increasing ion dose. This was explained by an additional de-phasing of coherent phonons by defect scattering. In graphite, the coherent acoustic phonon relaxation was accelerated due to additional scattering by defects. A linear dose-dependence of the decay rate was explained in terms of scattering of propagating acoustic phonons by single vacancies. Coherent LO phonon–plasmon coupled modes were annihilated by defect-induced carrier trapping.

Application of Time-Domain Vibrational Spectroscopy to the Study of Defects in Ion-Implanted Materials. M.Kitajima, M.Hase, K.Ishioka, K.Ushida: Nuclear Instruments and Methods in Physics Research B, 2003, 206, 99-102