OPTICAL-PROPERTIES OF B12P2

On polycrystalline B12P2 obtained by chemical vapor deposition on sili con substrates, the absorption edge and its low-energy tail were optic ally determined and analyzed with respect to interband transitions (in direct allowed transitions at 1.62, 1.80, 2.17, 2.46 and 2.75 eV) and ten gap-state-related transitions. Six of them exhibit energies which agree with electron traps generated by electron-phonon interaction in beta-rhombohedral boron. The number of one-phonon resonance frequencie s agrees with that group-theoretically determined. The two-phonon proc esses are quantitatively measured as well. Strong luminescence radiati on is superimposed on the FT-Raman spectrum, which differs qualitative ly from those traditionally measured. This difference is explained by fluctuating distortions of the icosahedra related to the strong optica l excitation of electrons from intrinsic electron traps.