Temperature‐dependent Raman scattering of natural and isotopically substituted PbS

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 .

Lattice properties ofPbX(X=S,Se,TeRomero1, Cardona2, Kremer3 et al. 2008Phys. Rev. BSelf Cite617391View full textAdd to dashboardCite

“…The (green) arrows at 100, 135, 175, 265 and 290 cm −1 also correspond to structure seen in the experimental spectra, although it is not clear whether the 135cm −1 structure is due to scattering by two phonons or forbidden scattering by one LO phonon. 13 A peak is also observed in the measured spectra at ∼ 90 cm −1 (Ref. 31).…”

“…Ref. 13. Two kinds of second order processes are possible, one in which the frequencies of the two phonons add (sum processes) and the other in which they subtract (difference processes).…”

“…The blue arrows mark structure which is weakly observed (except for the strong 430 -460 cm −1 peaks) in the Raman spectrum of PbS [ at ∼ 150, 180, 200, 220, 250, 320, 340, 430, 460 cm −1 ]. 13 The green arrows indicate possible structure related to the spectra published in Refs. 31 and 32…”

Nanostructured titania films sensitized by quantum dot chalcogenides

“…Lead sulfide crystallizes in rock salt structure precluding first-order Raman scattering from phonons near the centre of the Brillouin zone ( k = 0). However, the formally 'forbidden' LO scattering at 200 to 215 cm -1 may become allowed under conditions of resonant or quasi-resonant Raman excitation via the Fröhlich interaction, while appreciable contributions may also arise at these frequencies from two-phonon scattering of longitudinal acoustic and transverse optical modes in PbS [ 22 ]. A characteristic broad Raman band has been also reported at approximately 430 cm -1 due to 2 LO scattering in PbS [ 22 ], which, however, cannot be safely discriminated in the PbS/TiO 2 spectra due to the additional contribution of the rutile TiO 2 phonon at approximately 447 cm -1 .…”

Electronic, vibrational, and thermodynamic properties of metacinnabarβ-HgS, HgSe, and HgTe

“…A direct consequence of the up-bending is the fact that the corresponding peak in the second order Raman spectrum is not centered at 2 ϫ 105= 210 cm −1 but somewhat higher ͑228 cm −1 at 12 K͒. 54 In contrast, for GaAs, a typical downbending case, the two LO-phonon peak is shifted down by as much as 5 cm −1 with respect to twice the frequency of the LO phonons at ⌫. 55 Effects of the upwards bending on the phonon line widths will be discussed below.…”