Temperature Dependence of the Raman Spectrum and the Depolarization Spectrum of AmorphousAs2S3

Abstract

The polarized Stokes and anti-Stokes Raman spectrum of amorphous As2S3 has been measured at several temperatures in the range 20 ".". 8 'K with a He-Ne laser, and at room temperature with a c.w. dye laser. Using the Shuker -Gammon data-reduction method, the approximate density of vibrational states has been determined from the Raman spectra and has been found to be temperature independent.A new type of spectrum, the depolarization spectrum, has been measured for amorphous As2S, . The depolarization spectrum has been defined to be the dispersion of the Raman depolarization ratio. The measured Raman and depolarization spectra have been used to test the validity of the two structural models of vitreous As, S, proposed to date, namely: the planar-random-network model of Bermudez and the molecular model of Lucovsky and Martin. It has been shown that both models can be used to calculate Raman spectra in reasonable agreement with experiment while only the molecular model is compatible with the observed depolarization spectrum, Further, it has been demonstrated that the depolarization spectrum, not the Raman spectrum, provides a test of the applicability of the Shuker-Gammon data-reduction technique to a given amorphous solid. The low-temperature (~20 'K) Raman and room-temperature infrared transmission spectra of orpiment, the crystalline form of As, S3, have been measured. Several lines unresolved in previously reported room-temperature Raman spectra of orpiment have been resolved in the low-temperature spectra. The envelope of the approximate density of vibrational states of orpiment has been found to resemble remarkably the approximate density of vibrational states of amorphous AS2S3 This resemblance has been explained using the molecular model.

Raman spectroscopic and low-temperature calorimetric investigation of the low-energy vibrational dynamics of hen egg-white lysozyme

“…It has been found almost frequency independent in the investigated frequency range and to have a value of about 0.2 comparable to that previously obtained for amorphous systems [16]. The occurrence, at frequencies below 50 cm -1 , of a deviation of ρ(ν) from its constant value suggests a character of the modes lying in the Boson Peak frequency region slightly more polarized compared to the vibrations contributing to the second band in the Raman spectra.…”

Chalcogenide nanowires by evaporation–condensation

“…The peaks at 498 cm À1 and possibly 159 cm À1 corresponded to S-S vibrations possibly from either S 8 ring structures or S 2 groups, as reported by Nemanich [31] and Ward [32]. The dominant peak at 340 cm À1 is typical of amorphous As 2 S 3 , and has been attributed to intra-molecular As-S vibrations from the AsS 3 pyramidal units that comprise the random continuous network structure of this glass [33,34]. The three peaks found at 233, 222, and 182 cm À1 are in close proximity to those reported for homo-polar As-As vibrations from As 4 S 4 moieties which are also typically present in un-annealed, thermally evaporated, As 2 S 3 thin films [33,35].…”

New evidence of light-induced structural changes detected in As–S glasses by photon energy dependent Raman spectroscopy

“…3, the intensity of $320 cm À1 Raman mode is higher for As-rich As-S glass composition and the intensity of this mode increases with increasing exciting photon energy (1.58, 1.96, and 2.41 eV) that may be connected with light-induced planarity of the network. The maximum at 380 cm À1 is assigned to As-S-As water-like vibrations [14]. The exciting photon energies also influence the intensity of this peak in the differential Raman spectra of both As-S glasses.…”