Anisotropic optical properties of GeS investigated by optical absorption and photoreflectance

Abstract

We present a comprehensive study of bulk GeS optical properties and their anisotropy, by investigation of the fundamental band gap of the material and the energetically higher direct transitions.

Anisotropic Optical and Vibrational Properties of GeS

“…We found that the low-temperature (T = 5 K) optical band-gap absorption is governed by a single resonance related to the neutral exciton, while the corresponding emission is dominated by disorder/impurity-and/or phonon-assisted recombination processes. Moreover, both the RC and PL spectra are found to be linearly polarized along the armchair direction of the crystal, which is consistent with previous works [12,16,17]. The measured RS spectra as a function of temperature from 5 to 300 K are composed of six Raman peaks, the energies and symmetries of which are in agreement with phonon dispersion calculated using Density Functional Theory (DFT).…”

“…or absorption [17]. Moreover, according to the authors of [17], the X resonance can be related to the direct transition at the Γ point of the Brillouin zone (BZ), which is linearly polarized along the armchair crystallographic direction.…”

“…or absorption [17]. Moreover, according to the authors of [17], the X resonance can be related to the direct transition at the Γ point of the Brillouin zone (BZ), which is linearly polarized along the armchair crystallographic direction. Using DFT methods, we also calculated the band-gap energy at the Γ point of the BZ, which is on the order of 1.749 eV.…”

“…Despite the fact that the properties of GeS have been studied in several papers [12][13][14][15][16][17], most of these investigations were limited to a single particular experimental technique, e.g., photoluminescence (PL). In this work, we study anisotropic optical and vibrational properties of GeS with the aid of three types of optical experiments, moreover, performed with polarization resolution.…”

Anisotropic Optical And Vibrational Properties Of GeS

“…It is seen that both the emission and absorption signals of the X transitions are linearly polarized along the same direction (167 o and 170 o , respectively). The result confirms directly the same origin of the X feature apparent in both the PL and RC spectra, as previously reported independently for the emission 18 , photoreflectance 19 or absorption 20 . Moreover, according to Ref.…”