A Raman scattering study of self-assembled pure isotope Ge/Si(100) quantum dots

Use of self-assembled Ge/Si(100) quantum dots (QDs) grown from pure isotope Ge70 and Ge76 sources provides a unique possibility to experimentally deconvolute contributions from Ge QDs and Si substrate into the Raman spectrum. We demonstrate that raw Raman spectra of Ge/Si(100) QDs are dominated by the Si substrate. We further show that intermixing in the QDs depends on the dot size and is stronger in smaller dots, and that the Ge-rich area exists as a core of the dots. It is also shown that the amplitude of the Raman peak is not directly proportional to the number of the corresponding bonds.