Pressure-Induced Insulator–Metal Transition in Silicon Telluride from First-Principles Calculations

Abstract

Silicon telluride (Si2Te3) is a two-dimensional semiconductor with unique structural properties due to the size contrast between Si and Te atoms. A recent experiment shows that the material turns metallic under hydrostatic pressure, while the lattice structure of the metallic phase remains to be identified. In this paper, we propose two metallic phases, M1 and M2, of Si2Te3 using the evolution algorithm and firstprinciples density functional theory (DFT) calculations. Unlike the presence of Si-Si dimers in the semiconducting (SC) phase, both M1 and M2 phases have individual Si atoms, which play important roles in the metallicity. Analysis of structural properties, electronic properties, dynamical as well as thermal stability is performed. The energies of these new structures are compared with the SC phase under the subsequent hydrostatic pressure up to 12 GPa. The results show that M1 and M2 phases have lower energies under high pressure, thus elucidating the appearance of the metallic phase of Si2Te3. In addition, the external pressure causes the SC phase to have an indirect-direct-indirect bandgap transition. Analysis of Raman spectra of the SC phase at a different pressure shows the shifting of the major Raman peaks, and finally disappearing confirms the phase transition. The results are in good agreement with the experimental observations. The understanding of the insulator-metal phase transition increases the potential usefulness of the material system.

Chemical Reactions and Phase Stabilities in the Si–Te System at High Pressures and High Temperatures

“…The Te 8 @(Si 38 Te 8 )-type clathrate was also obtained and quenched to atmospheric pressure from the starting Si/Te composition of 38:16. We found no evidence for the formation of any phases of SiTe and Si 2 Te 3 reported earlier from theoretical predictions. ,− , …”

“…We found no evidence for the formation of any phases of SiTe and Si 2 Te 3 reported earlier from theoretical predictions. 5,[10][11][12]14 The F-centered clathrate Te 7+x Si 20−x (cF) was identified for the compositional mix of Si 38 /Te 16 , where it formed simultaneously with the Te 8 @(Si 38 Te 8 )-type clathrate after the hexagonal phase disappeared (Figure S2). At higher temperatures, the Te 8 @(Si 38 Te 8 )-type clathrate is favored and is retained on cooling.…”

“…Two metallic layered phases (triclinic and hexagonal) were proposed as candidates for the high-pressure polymorph of Si 2 Te 3 . 14 The Si 2 dumbbells are absent in both of them.…”

“…All of these observations suggest that the formation of SiTe from Si and α-Si 2 Te 3 could be facilitated by the structural instability of the latter at pressures below 10 GPa. Two metallic layered phases (triclinic and hexagonal) were proposed as candidates for the high-pressure polymorph of Si 2 Te 3 . The Si 2 dumbbells are absent in both of them.…”

First-Principles Investigations on the Semiconductor-to-Metal Phase Transition of 2D Si2Te3 for Reversible Resistive Switching

“…23 The recent theoretical study identified two different metallic phases of Si 2 Te 3 by using density functional theory (DFT) calculations with the evolution algorithm. 24 The study proposed that the key of the semiconductor-to-metal transition (SMT) of Si 2 Te 3 is that Te forms bonds with single Si atoms instead of bonds with Si−Si dimers, which can be observed in the semiconducting phase. However, they failed to explain why the formation of the single Si−Te bond could lead to the SMT of Si 2 Te 3 .…”