Anisotropic Optical Properties of 2D Silicon Telluride. (2020)

• Record Type: Journal Article
• Authors: Bhattarai, Romakanta; Chen, Jiyang; Hoang, Thang B.; Cui, Jingbiao; Shen, Xiao
• Is Part Of: MRS advances. Volume 5:Number 35/36(2020)
• Page Start: 1881
• Page End: 1889
• Publication Date: 2020
• Subjects: 2D materials, -- optical properties, -- modelings; Electrical engineering -- Congresses; Physics -- Congresses; Materials -- Research -- Congresses; Materials science -- Congresses; 620.11
• DOI: 10.1557/adv.2020.186
• Languages: English
• ISSNs: 2059-8521

Abstract

ABSTRACT: Silicon telluride (Si2 Te3 ) 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 Si2 Te3 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 Si2 Te3 . 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 Si2 Te3 multilayers.