Increases in Si content and the calculated Raman spectra acquired from the Si_xGe_（1-x） alloys reveal that the frequencies of the Ge-Si and Si-Si modes are up-shifted obviously,meanwhile that of the Ge-Ge optical mode is down-shifted,which is strongly dependent on their microstructural changes.The linear decrease and increase caused by their force constant（bond lengths and bond angles） changes,which can be used as a fingerprint to identify the average Si content.The complex microstructural changes induced by increasing Si content can be clearly displayed by Raman spectra transformation.
