The solid-state reaction of Ni on strained and relaxed (001) Si0.8Ge0.2 has been studied by micro-Raman scattering with a particular emphasis on the influence of Ge-rich Si1-zGez segregation in NiSi1-uGeu films. Raman scattering is found to be a sensitive and useful tool to probe such Ge-rich Si1-zGez segregation that takes place preferentially at the germanosilicide/Si1-xGex interface. From Raman measurements, the composition of Ge within Ge-rich Si1-zGez grains formed due to prolonged rapid thermal annealing can be mapped and the results show consistency with transmission electron microscopy. We have also observed that both shorter annealing time and addition of Pt can effectively suppress the Ge segregation at the interface. Furthermore, Raman scattering can clearly detect the onset temperature of Ge segregation for different thermal annealing conditions. (C) 2004 The Electrochemical Society.