Abstract
Bismuth telluride (Bi2Te3) has garnered significant interest in thermoelectric applications and three-dimensional topological insulators due to its unique electronic, transport, and thermal properties. Bi2Te3 and Sb2Te3 chalcogenide compounds have the same crystal structure. While Sb2Te3 has been shown to be a prototypical phase change memory (PCM) compound along the pseudobinary tie-line of Ge-Sb-Te alloys, whether Bi2Te3 can also exhibit PCM functionality is still not well established. In this work, a systematic study on the structural, dynamical, and electronic properties of amorphous Bi2Te3 during the quenching process has been performed by using ab initio molecular dynamics simulations. Pair correlation function, coordination number, bond-angle distribution functions, and a novel atomistic cluster alignment method are used to explore the structural characteristics of Bi2Te3 as a function of temperature. Our study shows that there are many distorted octahedral clusters in amorphous Bi2Te3. In comparison with the local structures in Sb2Te3, we found that the degree of distortion of the octahedrons in the Bi2Te3 system is smaller than that in Sb2Te3 system. Moreover, the changes in the dynamical properties of Bi2Te3 from liquid to glassy state are also explored. The approximate range of liquid-to-glass transition temperature is determined to be between 673 and 723 K. The electronic properties of Bi2Te3 and Sb2Te3 are also analysed by density-of-states and Bader charge calculations, both of them in glass state are semiconductors. Our studies provide useful insights into the local structure and dynamical properties of Bi2Te3 at the atomistic level during the fast cooling process, and suggest that the compound can be a candidate for PCM materials.
Highlights
Phase change memory (PCM) materials can repeat ultrafast and reversible phase changes between amorphous and crystalline states via appropriate heating processes [1, 2]
Liquid and amorphous states of Bi2Te3 were modelled by ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT), using the Vienna ab initio simulation package (VASP) code [19, 20]
The first peaks in total pair correlation functions (PCF) become stronger with decreasing temperature, demonstrating that the system is more ordered at the glassy state
Summary
Phase change memory (PCM) materials can repeat ultrafast and reversible phase changes between amorphous and crystalline states via appropriate heating processes [1, 2]. Bi2Te3 and Sb2Te3 compounds have the same rhombohedral crystal structure with space group D35d (R3 m), and the atomic layers are arranged in the order of Te1-Bi(Sb)-Te2-Bi(Sb)-Te1 in the hexagonal cell [5]. Both compounds have been shown to exhibit excellent thermoelectric performance, and have played an important role in the thermoelectric studies over the past few decades [6,7,8]. Since Sb2Te3 is the prototypical PCM along the pseudobinary tie-line of Ge-Sb-Te alloys, and has been widely studied and applied [12,13,14,15], it is of great interest to explore whether Bi2Te3 can be a good candidate for PCM
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