On the origin of the Boson peak in the Raman scattering spectrum of As2S3 glass

Paper presents a Raman study of H-and O-doped vitreous As2S3, with emphasis on the frequency region below 100 cm-1. Authors found that while doping with H up to 1660 ppm does not affect the Raman spectrum of As2S3 glass, similar doping with O results in an increase of the intensity of the Boson peak. Doping with O also results in an increase in intensity of the 310 cm-1 peak, due to asymmetric vibrations of the glass network. A comparative study of the Raman spectra of glassy and crystalline As2S3 indicates a matching of the broad glassy Boson peak with the narrow crystalline peak at 26 cm-1. Authors suggest that asymmetric optical vibrations of the AsS3 pyramids with respect to each other may be related to the Boson peak. While the 310 cm-1 peak is due to vibrations of the pyramids involving intramolecular (covalent) primary bonds, the Boson peak is suggested to originate, in part, on a translatory vibration involving intermolecular (van der Waals) secondary bonds between the S atoms and their surroundings. 23 refs.