The effects of defects upon coherent phonons in ion-implanted Bi, graphite and GaAs were studied. Ultra-fast dynamics of coherent phonons in the time-domain were investigated by means of femtosecond pump–probe reflectivity techniques. For Bi, the de-phasing rate of the A1g phonon increased linearly with increasing ion dose, which was explained by the additional de-phasing of coherent phonons by the defect scattering. For graphite, the coherent acoustic phonon relaxation was also accelerated due to the additional scattering by defects. The linear dose-dependence of the decay rate was understood as scattering of propagating acoustic phonons by single vacancies. The

coherent LO phonon–plasmon coupled modes were annihilated by the 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