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.
@article{arxiv.1606.06953,
title = {Anisotropic Optical Properties of Layered Germanium Sulfide},
author = {Dezhi Tan and Hong En Lim and Feijiu Wang and Nur Baizura Mohamed and Shinichiro Mouri and Koirala Sandhaya and Wenjing Zhang and Yuhei Miyauchi and Mari Ohfuchi and Kazunari Matsuda},
journal= {arXiv preprint arXiv:1606.06953},
year = {2016}
}