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Exciton–phonon interactions in the Cs 3 Bi 2 I 9 crystal structure revealed by Raman spectroscopic studies
Author(s) -
Nilă Andreea,
Baibarac Mihaela,
Matea Adelina,
Mitran Raul,
Baltog Ioan
Publication year - 2017
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201552805
Subject(s) - exciton , photoluminescence , raman spectroscopy , phonon , raman scattering , crystal (programming language) , materials science , excitation , molecular physics , photoluminescence excitation , spectral line , chemistry , condensed matter physics , optics , physics , optoelectronics , computer science , programming language , quantum mechanics , astronomy
The enhancement of the Raman scattering in Cs 3 Bi 2 I 9 is evaluated by the ratio I T / I 300 K between the relative intensities of the Raman line peaked at 146 cm −1 , when the spectra are recorded in the temperature range of 88–300 K, as a signature of exciton–phonon interactions. In the resonant and nonresonant conditions, excitation wavelengths 476, 561, and 660 nm, respectively, are used in order to overlap with great accuracy the bands disclosed by diffuse reflection, photoconductivity (PC), photoluminescence (PL), and photoluminescence excitation (PLE) spectra. Based on the experimental analyses, the strength of exciton–phonon interaction is dependent on the defects in the crystal and the type–range interaction of the excitations in an independent Bi 2 I 9 3− cluster. The noticeable PL band, attributed to excitons trapped on different stacking faults, manifests some defects in crystal that diminish the movement of excitons. This effect significantly decreases the overlaps of excitons with the phonons, resulting in a reduced exciton–phonon coupling.