Near-surface Raman scattering in germanium clusters and ultrathin amorphous films

Vibrational studies of Ge clusters and ultrathin amorphous semiconducting films have been performed in situ in ultrahigh vacuum. A combination of multichannel and interference-enhanced methods has allowed Raman scattering of a solid to be achieved at film thicknesses of less than an equivalent monolayer coverage. Substantial changes in the amorphouslike Raman spectral form with decreasing film thickness indicate the increasing role of near-surface dangling bonds and bond-angle disorder on the phonon density of states. This is confirmed by H chemisorption effects.