1 research outputs found
The Role of Interdiffusion and Spatial Confinement in the Formation of Resonant Raman Spectra of Ge/Si(100) Heterostructures with Quantum-Dot Arrays
The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beam
epitaxy in an apparatus integrated with a chamber of the scanning tunneling
microscope into a single high-vacuum system are investigated using Raman
spectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes are
considerably enhanced upon excitation of excitons between the valence band
and the conduction band (the E1 and E1 +
transitions). This makes it possible to observe the Raman spectrum of very
small amounts of germanium, such as one layer of quantum dots with a germanium
layer thickness of 10 \r{A}. The enhancement of these modes suggests a strong
electron-phonon interaction of the vibrational modes with the E1 and E1 +
excitons in the quantum dot. It is demonstrated that the frequency
of the Ge-Ge mode decreases by 10 cm^-1 with a decrease in the thickness of the
Ge layer from 10 to 6 \r{A} due to the spatial-confinement effect. The optimum
thickness of the Ge layer, for which the size dispersion of quantum dots is
minimum, is determined.Comment: 14 pages, 9 figure