Thermally Induced Structural Evolution and Nanoscale Interfacial Dynamics in Layered Metal Chalcogenides

TL;DR

This study combines in situ TEM and DFT calculations to explore how layered metal chalcogenides structurally evolve and undergo sublimation at the nanoscale when heated, highlighting defect roles and interfacial dynamics.

Contribution

It provides new insights into the temperature-dependent nanoscale dynamics, defect roles, and sublimation pathways in layered chalcogenides, informing future material design.

Findings

Polygonal nanopores form via Te dissociation at specific sites.

Heterostructures exhibit reduced thermal stability and distinct sublimation pathways.

Native antisite defects like TeBi influence sublimation mechanisms.

Abstract

Layered chalcogenides including Bi2Te3, Sb2Te3, Bi-Sb-Te ternary alloys and heterostructures are known as great thermoelectric, topological insulators and recently highlighted as plasmonic building blocks beyond noble metals. Here, we conduct a joint in situ transmission electron microscopy (in situ TEM) and density functional theory (DFT) calculations to investigate the temperature dependent nanoscale dynamics, interfacial properties and further identifying the role of native defects and edge configurations in anisotropic sublimations of Bi2Te3-Sb2Te3 in-plane heterostructure and Sb2-xBixTe3 alloy. Structural dynamics including edge evolution, formation, expansion, and coalescence of thermally induced polygonal nanopores are reported. The nanopores appear to be initiated by preferential dissociation of chalcogenide species (Te) from the center, heterointerface and edges in the heterostructure and only from the outer edges in the alloy counterpart. This results in a reduced thermal stability and significantly different sublimation pathways of the heterostructure. Furthermore, triangular and quasi hexagonal configurations are observed to be the dominant nanopores configurations in the heterostructure. Additionally, our DFT calculations provide a mechanistic understanding on the role of native defects and edge formation energies, revealing the antisite defects TeBi to be the dominant native defect in a Te-rich condition and playing a key role on the defects assisted sublimation. These findings significantly impact our understanding of controlling the nanoscale sublimation dynamics and can ultimately assist us in designing tunable low-dimensional chalcogenides.