Anisotropic optical properties of single Si2Te3 nanoplates

Jiyang Chen,Jingbiao Cui,Romakanta Bhattarai,Thang Hoang,Xiao Shen

doi:10.1038/s41598-020-76265-1

Jiyang Chen, Jingbiao Cui + Show 3 more

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https://doi.org/10.1038/s41598-020-76265-1

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Abstract

We report a combined experimental and computational study of the optical properties of individual silicon telluride (Si2Te3) nanoplates. The p-type semiconductor Si2Te3 has a unique layered crystal structure with hexagonal closed-packed Te sublattices and Si–Si dimers occupying octahedral intercalation sites. The orientation of the silicon dimers leads to unique optical and electronic properties. Two-dimensional Si2Te3 nanoplates with thicknesses of hundreds of nanometers and lateral sizes of tens of micrometers are synthesized by a chemical vapor deposition technique. At temperatures below 150 K, the Si2Te3 nanoplates exhibit a direct band structure with a band gap energy of 2.394 eV at 7 K and an estimated free exciton binding energy of 150 meV. Polarized reflection measurements at different temperatures show anisotropy in the absorption coefficient due to an anisotropic orientation of the silicon dimers, which is in excellent agreement with theoretical calculations of the dielectric functions. Polarized Raman measurements of single Si2Te3 nanoplates at different temperatures reveal various vibrational modes, which agree with density functional perturbation theory calculations. The unique structural and optical properties of nanostructured Si2Te3 hold great potential applications in optoelectronics and chemical sensing.

Highlights

We report a combined experimental and computational study of the optical properties of individual silicon telluride (Si2Te3) nanoplates
At temperatures below 150 K, a direct band structure is observed with a band gap value of 2.394 eV at 7 K
Polarized reflection measurements at different temperatures show an anisotropic behavior that is related to an anisotropy in the dielectric functions along different crystal directions due to the orientation of the Si–Si dimer

Summary

Introduction

We report a combined experimental and computational study of the optical properties of individual silicon telluride (Si2Te3) nanoplates. Polarized reflection measurements at different temperatures show anisotropy in the absorption coefficient due to an anisotropic orientation of the silicon dimers, which is in excellent agreement with theoretical calculations of the dielectric functions. Shen et al.[5] reported the variabilities of the electronic properties of nanostructured S i2Te3, including the tunable bandgap and band structures due to different Si–Si dimer orientations. The complication of the structural properties of Si2Te3 at low dimensions due to the orientation of the silicon dimers at different temperatures and strains could lead to strikingly different optical or electronic properties[5]. Polarized reflection measurements at different temperatures show an anisotropic behavior that is related to an anisotropy in the dielectric functions along different crystal directions due to the orientation of the Si–Si dimer. The measured polarized Raman and reflection results agree well with the first-principles calculations, which reveals the role of the Si–Si dimer orientations

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