The frequencies of the Si-Si, Si-Ge, and Ge-Ge Raman modes in (Formula presented)(Formula presented)(Formula presented) alloys with y⩽0.03 have been measured. All frequencies are found to increase as a function of the carbon concentration. Within experimental error, this dependence is linear with a large slope, which can be explained qualitatively in terms of the large bond distortions caused by the lattice mismatch between (Formula presented)(Formula presented) and diamond. Good numerical agreement with theoretical predictions is obtained if the mode frequencies are plotted as a function of the substitutional carbon fraction determined from Rutherford backscattering studies. For the “Si-Si” mode, the magnitude of the carbon contribution to the bond-distortion dependence of the Raman frequency shift is found to be 15 times larger than the Ge contribution. This disagrees with the 8-to-1 strain compensation ratio predicted form Vegard’s law, but agrees well with theoretical predictions of this ratio.
|Original language||English (US)|
|Number of pages||7|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jan 1 1996|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics