A Raman study of high-pressure phases of lead chalcogenides PbX (X=S, Se, Te)

Abstract

Pressure-induced phase transitions of lead chalcogenides were studied by Raman spectroscopy. The number of Raman modes observed for the first high-pressure phases was found to be significantly less than expected from selection rules for the proposed GeS-type orthorhombic structure. The observations are consistent with the alternative assignment as CrB-type. In the case of PbS, the disappearance of the intermediate-phase Raman lines in the pressure range of 19–25 GPa, i.e., in the vicinity of the orthorhombic to CsCl-type phase transition, is accompanied by a strong increase in a structureless background. The Raman background is attributed to light scattering by charge carriers in the metallic CsCl-type phase.

^†This paper was presented at the XLVI^th European High Pressure Research Group (EHPRG 46) Meeting, Valencia (Spain), 7–12 September, 2008.

Keywords:

• Raman scattering
• lead chalcogenides
• pressure
• phonons
• semiconductor to metal transition

Acknowledgements

The work was supported by the Russian Foundation for Basic Research (Grant no. 05-02-16780, 08-02-00437 and 07-08-00338). Yu.S.P. acknowledges support by the Max-Planck Society.

Notes

^†This paper was presented at the XLVI^th European High Pressure Research Group (EHPRG 46) Meeting, Valencia (Spain), 7–12 September, 2008.