SECOND ORDER RAMAN SCATTERING IN CRYSTALLINE SULPHUR SELENIUM AND TELLURIM

The second order Raman spectrum of orthorhombic (o-) S is reported and compared with the spectrum of monoclinic (m-) Se. The spectra of these ring systems exhibit very similar structure. Three regions of scattering are observed, two of which suggest a predominance of overtone scattering. The features of the other region arise from combination processes. A comparison between the high frequency bands of trigonal(t-) Te, t-Se, m-Se and o-S is also presented. Differences in these spectra are qualitatively explained in terms of the molecular unit of the crystal (ring or chain) and changes in inter-unit and intra-unit coupling

RAMAN SCATTERING IN ANNEAL STABLE AMORPHOUS SILICON

First order Raman scattering measurements are reported on anneal stable amorphous Si prepared by chemical vapor deposition. The results in dicate substantial modifications of the Raman spectra relative to a-Si prepared by other methods. The results indicate improved short range order in CVD a-Si resulting from a narrowing of the bond angle distribution. Similarties t o a-Si1-xHx spectra suggest improved short order in the hydrogen alloys

THE VIBRATIONAL SPECTRA OF CRYSTALLINE AND AMORPHOUS PHOSPHOROUS

Inelastic neutron scattering measurements are reported on polycrystalline orthorhombic black phosphorous (o-black P) and on amorphous red phosphorous (a-red P). The a-red P results indicate that the vibrational density of states is composed of three distinct spectral bands, with gaps or pseudo-gaps separating these regions. While the high frequency phonon band of o-black P occurs near to that of a-red P, considerable differences exist at lower frequencies. In particular the lowest band in a-red P is less structured and shows a strong shift towards smaller energies i.e. a pronounced softening of the lower part of the a-red spectrum is displayed. The vibrational densities of states have been employed to determine the lattice specific heats and Debye temperatures

OPTICAL ABSORPTION AND STRUCTURAL ORDER IN SPUTTERED AMORPHOUS PHOSPHORUS

Optical absorption measurements are reported for rf sputtered a-P films prepared under conditions of variable substrate temperature. Variations in the optical gap with Ts are similar to changes in the Raman scattering and x-ray diffraction spectra. The results suggest that intermediate-range order plays an important role for the structural, vibrational and optical properties for more ordered a-P films. Photostructural effects in As-chalcogenides which exhibit analogous behavior also suggest modifications of intermediate-range order