The optical response of bulk germanium sulfide (GeS) is investigated systematically using different polarization-resolved experimental techniques, such as photoluminescence (PL), reflectance contrast (RC), and Raman scattering (RS). It is shown that while the low-temperature (T=5 K) optical band-gap absorption is governed by a single resonance related to the neutral exciton, the corresponding emission is dominated by the disorder/impurity- and/or phonon-assisted recombination processes. Both the RC and PL spectra are found to be linearly polarized along the armchair direction. The low and room (T=300 K) temperature RS spectra consist of six Raman peaks identified with the help of Density Fuctional Theory (DFT) calculations: Ag1, Ag2, Ag3, Ag4, B1g1, and B1g2, which polarization properties are studied under four different excitation energies. We found that the polarization orientations of the Ag2 and Ag4 modes under specific excitation energy can be useful tools to determine the GeS crystallographic directions: armchair and zigzag.
@article{arxiv.2110.14977,
title = {Anisotropic Optical And Vibrational Properties Of GeS},
author = {Natalia Zawadzka and Łucja Kipczak and Tomasz Woźniak and Katarzyna Olkowska-Pucko and Magdalena Grzeszczyk and Adam Babiński and Maciej R. Molas},
journal= {arXiv preprint arXiv:2110.14977},
year = {2022}
}