Temperature-dependent Raman scattering of natural and isotopically substituted PbS

TL;DR

This study investigates how temperature affects Raman spectra of natural and isotopically substituted PbS, revealing insights into phonon behavior through experimental data and ab initio calculations.

Contribution

It provides the first detailed temperature-dependent Raman spectra of PbS with isotopic variations and compares them with theoretical lattice dynamics calculations.

Findings

Temperature influences the two-phonon Raman band at ~430 cm-1.

Resonance effects enable Raman detection despite forbidden first-order scattering.

Isotopic substitution affects phonon frequencies and intensities.

Abstract

Lead sulfide is an important semiconductor that has found technological applications for over a century. Raman spectroscopy, a standard tool for the investigation and characterization of semiconductors, has limited application to this material because of the forbidden nature of its first order scattering and its opacity to visible lasers. Nevertheless, useful vibrational spectra from two-phonon processes are obtained with red lasers, probably because of a resonance in the concomitant electronic transitions. Here we report temperature dependent spectra, covering the 10-300 K range, for two samples with different sulfur isotopic compositions. The results are analyzed by comparison with ab initio calculations of the lattice dynamics of PbS and the corresponding densities of one and two-phonon states. Emphasis is placed on the analysis of the two phonon band centered at ~430 cm-1.