Anisotropic Optical Properties of 2D Silicon Telluride
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MRS Advances © 2020 Materials Research Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercialShareAlike licence (http://creativecommons.org/licenses/by-ncsa/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the same Creative Commons licence is included and the original work is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use. DOI: 10.1557/adv.2020.186
Anisotropic Optical Properties of 2D Silicon Telluride Romakanta Bhattarai,1 Jiyang Chen,1 Thang B. Hoang,1 Jingbiao Cui,2 and Xiao Shen1 1
Department of Physics and Materials Science, University of Memphis, Memphis, TN 38152, USA
2
Department of Physics, University of North Texas, Denton, TX 76201, USA
ABSTRACT Silicon telluride (Si2Te3) is a silicon-based 2D chalcogenide with potential applications in optoelectronics. It has a unique crystal structure where Si atoms form Si-Si dimers to occupy the “metal” sites. In this paper, we report an ab initio computational study of its optical dielectric properties using the GW approximation and the Bethe-Salpeter equation (BSE). Strong in-plane optical anisotropy is discovered. The imaginary part of the dielectric constant in the direction parallel to the Si-Si dimers is found to be much lower than that perpendicular to the dimers. The optical measurement of the absorption spectra of 2D Si2Te3 nanoplates shows modulation of the absorption coefficient under 90-degree rotation, confirming the computational results. We show the optical anisotropy originates from the particular compositions of the wavefunctions in the valence and conduction bands. Because it is associated with the Si dimer orientation, the in-plane optical anisotropy can potentially be dynamically controlled by electrical field and strain, which may be useful for new device design. In addition, BSE calculations reduce GW quasiparticle band gap by 0.3 eV in bulk and 0.6 eV in monolayer, indicating a large excitonic effect in Si 2Te3. Furthermore, including electron-hole interaction in bulk calculations significantly reduces the imaginary part of the dielectric constant in the out-of-plane direction, suggesting strong interlayer exciton effect in Si2Te3 multilayers.
INTRODUCTION Since the last decade, two-dimensional materials have drawn a lot of interest in potential applications and fundamental sciences. Many 2D materials: graphene [1-3], transition-metal dichalcogenides such as MoS2 [4], phosphorene [5,6], and more have been fabricated, and the investigations revealed interesting properties different from their bulk forms. Among the many properties of 2D materials, the optical properties are
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particularity notable, as the low dimensionality significantly
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