Anisotropic Optical Properties and Vibrational Characteristics of 2D Silicon Telluride Nanoplates

The p-type semiconductor silicon telluride (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. Here, we report a combined experimental and computational study of the optical properties of individual Si2Te3 nanoplates (NPs). 2D Si2Te3 NPs with thickness of tens to hundreds of nanometers and diameter of tens of micrometers are synthesized by the chemical vapor deposition technique. Polarized reflection measurements at different temperatures show a 90-degree periodic change in the absorption coefficient, which indicates an anisotropic orientation of the Si-Si dimers and is in agreement with the theoretical calculation of the dielectric constants. Polarized and spatial Raman mapping measurements of single Si2Te3 NPs at different temperatures reveal various vibrational modes, which are in agreement with the Density Functional Theory calculation.