High Pressure Structural Behavior of Silicon Telluride (Si2Te3) Nanoplates

TL;DR

This study investigates the high-pressure structural and electronic behavior of silicon telluride (Si2Te3) using experimental X-ray diffraction and theoretical calculations, revealing phase transitions, potential metallization, and vibrational properties.

Contribution

It provides new insights into the phase transitions, structural stability, and electronic changes of Si2Te3 under high pressure through combined experimental and computational approaches.

Findings

Si2Te3 transitions from trigonal to hexagonal structure below 1 GPa

Possible new phase transition observed above 8.5 GPa

Metallization occurs above 9.1 GPa, consistent with experimental spectra

Abstract

The high-pressure behavior of silicon telluride (Si2Te3), a two-dimensional (2D) layered material, was investigated using synchrotron X-ray powder diffraction in a diamond anvil cell to 11.5 GPa coupled with first-principles theory. Si2Te3 undergoes a phase transition at < 1 GPa from a trigonal to a hexagonal crystal structure. At higher pressures (> 8.5 GPa), X-ray diffraction showed the appearance of new peaks possibly coincident with a new phase transition, though we suspect Si2Te3 retains a hexagonal structure. Density functional theory calculations of the band structure reveal metallization above 9.1 GPa consistent with previous measurements of the Raman spectra and disappearance of color and transparency at pressure. The theoretical Raman spectra reproduce the prominent features of the experiment, though a deeper analysis suggests that the orientation of Si dimers dramatically influences the vibrational response. Given the complex structure of Si2Te3, simulation of the resulting high-pressure phase is complicated by disordered vacancies and the initial orientations of Si-Si dimers in the crushed layered phase.