ABOVE THE BAND-GAP STRUCTURES IN GE NANOPARTICLES - OPTICAL-ABSORPTION SPECTRA

We report absorption measurements on Ge nanoparticles in the range 0.6 -6 eV. By reducing the dot average radius to about 13 Angstrom one obs erves a relevant blue-shift of the E(1) + Delta(1) and E(2) peaks and a change of the oscillator strength of the two main structures. Simula tions using effective-medium theories have been carried out and the em bedding matrix contribution to the measured properties has been evalua ted. The different behaviour of the absorption peaks E(1), E(1) + Delt a(1) and E(2) under quantum confinement has been related to their spec ific nature within the whole Brillouin zone.