Nanostructuring of Single Crystalline SnSb 2 Te 4 and GeBi 2 Te 4 van der Waals Compounds by High-Energy Ball Milling

Abstract

Thermoelectric materials, an important class within the semiconductor family for energy conversion, have been extensively studied in bulk form. However, growing interest in nanoscale materials driven by the quantum confinement effect has made it increasingly important to investigate how their properties change at reduced dimensions. In this work, we demonstrate the successful fabrication of nanosized ternary van der Waals (vdW) compounds SnSb 2 Te 4 and GeBi 2 Te 4 from their high-quality single crystals using High Energy Ball Milling (HEBM) for the first time. Here we discuss the effect of milling variables, i.e., materials of the milling container or grinding vessel and balls, milling medium (wet vs. dry), milling time, etc. The scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analysis of the fabricated nanopowders reveals a strong sensitivity of the samples to the grinding vessel and ball materials, which introduces significant contamination during the milling process. Upon the milling time, this contamination can significantly impact the final composition of the powder, which is undesirable for functional semiconductor materials, where electronic properties are highly sensitive to impurities. Using different types of milling equipment, we demonstrate that nanoscale refinement with minimal impurity can be achieved simply by selecting appropriate milling materials, without modifying the target material or using protective agents. This result is particularly valuable for the preparation of high-purity nanoscale thermoelectric materials based on single-crystalline layered vdW compounds by the top-down method.