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The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beamepitaxy in an apparatus integrated with a chamber of the scanning tunnelingmicroscope into a single high-vacuum system are investigated using Ramanspectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes areconsiderably enhanced upon excitation of excitons between the valence band$\Lambda_3$ and the conduction band $\Lambda_1$ (the E1 and E1 + $\Delta_1$transitions). This makes it possible to observe the Raman spectrum of verysmall amounts of germanium, such as one layer of quantum dots with a germaniumlayer thickness of 10 \r{A}. The enhancement of these modes suggests a strongelectron-phonon interaction of the vibrational modes with the E1 and E1 +$\Delta_1$ excitons in the quantum dot. It is demonstrated that the frequencyof the Ge-Ge mode decreases by 10 cm^-1 with a decrease in the thickness of theGe layer from 10 to 6 \r{A} due to the spatial-confinement effect. The optimumthickness of the Ge layer, for which the size dispersion of quantum dots isminimum, is determined.

The Role of Interdiffusion and Spatial Confinement in the Formation of Resonant Raman Spectra of Ge/Si(100) Heterostructures with Quantum-Dot Arrays