Raman scattering measurements are used to characterize Co/Si, Co/Ge and CO/Si0.8Ge0.2 thin film reactions. For Co/Si samples, the phase transitions Co--CoSi--CoSi2 are identified by Raman spectroscopy. For Co/Ge samples, Raman features associated with Co5Ge 7 and CoGe2 phases were observed. For CO/Si0.8Ge0.2 samples, only CoSi was identified along with Ge enriched SiGe alloy peaks. No features associated with CoGe or Co(SiGe) were found.