Different quantum behavior of the E1 and E2 spectral structures in Ge nanocrystals

In this paper we report absorption measurements in the range 0.6-6.0 eV, performed at 77 K on Ge nanocrystals grown by a self-organization process applied to a semiconductor. Evidence of a relevant blueshift of E2 and weakening of E1 with size reduction is obtained. This behavior is interpreted in terms of quantum confinement in connection with the different nature of the two structures.