Second-order Raman scattering of small Ge particles in resonance with the E1 and E1+ Delta 1 edges.

Abstract

Second-order Raman spectra of Ge particles with sizes of about 10 nm have been studied under resonance with the ${\mathit{E}}_{1}$ and ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ edges. The obtained spectra are analyzed in terms of discrete electronic and vibrational energy levels and in terms of the surface phonon mode. The discreteness of those eigenstates yields a decrease in the scattering rate of holes due to the k\ensuremath{\sim}0 phonons in the small particles. A Raman band located just below the 2TO-phonon band is attributed to the scattering by two surface phonons.