Defect-Mediated Growth of Layered Lateral Bi₂Te₃–Sb₂Te₃–Bi₂Te₃ Heterostructures

Abstract

In-plane heterostructures of Bi2Te3-Sb2Te3 (BT-ST) have garnered significant interest owing to their topological properties and their applications as thermoelectric materials and in p-n junction devices. While various solution-based approaches have been employed in the past for heterostructure formation, using multistep methods, achieving one-step synthesis has been challenging. Herein, a successful synthesis of BT-ST heterostructure using a one-pot solution-based synthetic strategy is reported, where in situ generated Bi2Te3 nanosheet acts as a template to grow Sb2Te3. Furthermore, this strategy has been extended to form the double shell heterostructure of Bi2Te3-Sb2Te3-Bi2Te3 (BT-ST-BT). Control experiments by varying precursor ratio, time, and temperature have been conducted to elucidate the growth process. Cross-section high-angle annular dark field scanning-transmission electron microscope imaging reveals the existence of steps on the growth surface, providing clues to a screw-dislocation-mediated growth mechanism. To gain insights into the screw-dislocation-driven growth, atomic-resolution imaging has been carried out by using an aberration-corrected scanning-transmission electron microscope. The presence of screw dislocations is evident from the 2-layer defect at the interface, owing to which the usual quintuple-layer structure is perturbed by the formation of a 5-layer 7-layer structure. These dislocations contain Te-Bi/Sb layers and join the upper block of one-quintuple layer (Te-Bi/Sb) to the lower block of other quintuple layers (Bi/Sb-Te) via atom inversion and serve as attachment sites for further growth of Bi2Te3 onto the BT-ST heterostructure. The screw dislocations are found to originate from pristine Bi2Te3 and play a critical role in the overall growth process. Overall, this study demonstrates the versatility of a solution-based approach in designing multishell nanostructures and detailed analysis of interfaces, which provide insights into the atomic arrangement during the screw-dislocation-mediated growth mechanism. © 2024 American Chemical Society