Phonons in amorphous semiconductor superlattices

Raman scattering measurements on amorphous $a-\mathrm{Si}:\mathrm{H}/a-\mathrm{Si}{\mathrm{N}}_x:\mathrm{H}$ and $a-\mathrm{Si}:\mathrm{H}/a-\mathrm{Si}{\mathrm{O}}_x$ superlattices indicate the first observation of heterostructure effects on the phonons of noncrystalline solids. With decreasing thickness the $a-\mathrm{Si}:\mathrm{H}$ Raman spectra imply increased bond-angle disorder associated with interfacial induced modifications of network formation. The results suggest that interfacial bonding constraints in amorphous superlattices result in local disorder that qualitatively differs in character from that of crystalline systems.