Raman, optical-absorption, and transmission electron microscopy study of size effects in germanium quantum dots

Quantum confinement effects in Ge nanocrystals in the size range 26-130 Angstrom have been investigated both on the electronic joint density of states and Raman spectra. The high degree of crystallinity of the particles as well as the minimized interaction with the matrix allow detection of shift and broadening of the TO Raman peak, which can be compared with theoretical expectations based on phonon confinement. The evolution of Raman and absorption spectra and their dependence on the nanocrystal dimensions can be related