Anisotropic Optical Properties of Layered Germanium Sulfide

TL;DR

This paper investigates the anisotropic optical properties of layered germanium sulfide (GeS), demonstrating polarization-dependent Raman scattering and photoluminescence, supported by theoretical calculations, highlighting its potential for novel physical phenomena and device applications.

Contribution

It provides the first detailed analysis of GeS's anisotropic optical properties, combining experimental Raman and photoluminescence studies with density functional theory.

Findings

Polarized Raman peaks confirm crystal orientation.

Room temperature photoluminescence peak at 1.66 eV observed.

Anisotropic optical transition near the band edge identified.

Abstract

Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals an anisotropic optical transition near the band edge of GeS, which is also supported by the density functional theory calculations. This anisotropic layered GeS presents the opportunities for the discovery of new physical phenomena and will find applications that exploit its anisotropic properties.