Above the band gap structures in Ge nanoparticles: optical-absorption spectra

Summary We report absorption measurements on Ge nanoparticles in the range 0.6–6 eV. By reducing the dot average radius to about 13 ?, one observes a relevant blue-shift of theE ₁+Δ ₁ andE ₂ peaks and a change of the oscillator strength of the two main structures. Simulations using effective-medium theories have been carried out and the embedding matrix contribution to the measured properties has been evaluated. The different behaviour of the absorption peaksE ₁,E ₁+Δ ₁ andE ₂ under quantum confinement has been related to their specific nature within the whole Brillouin zone. The authors of this paper have agreed to not receive the proofs for correction.