Raman spectroscopy of carbon-induced germanium dots

Raman spectroscopy is used to study C and Ge diffusion in multilayers of C- induced Ge dots deposited on Si(100). The initial Ge content is fixed to 2 ML and the C precoverage varied from 0.1 to 0.3 ML. The resulting concentra tion of isolated substitutional C atoms depends on the C precoverage and th e thermal annealing performed after growth. C atoms are mostly localized in the areas around the dots, due to the repulsive Ge-C interaction. When C i s added, the interface around the burried dots becomes sharper, and less Ge alloying occurs. C mainly increases the strain contrast around the dots an d induces a strain-enhanced Ge interdiffusion, even at 650 degreesC. At 800 degreesC, Ge and C interdiffuse simultaneously. (C) 2001 American Institut e of Physics.