Controlled growth of 3D topological insulator BiSb(Te1−ySey)3 nanocrystals via chemical vapor transport

Abstract

The structural and electrical properties of thin nanocrystals of the 3D topological insulator BiSb(Te_1−ySe_y)₃ (y = 0, 0.01, 0.02, …, 0.09) have been investigated. The nanostructures were synthesized from bulk parent BiSb(Te_1−ySe_y)₃ polycrystalline powder on different substrate materials using the bottom-up chemical vapor transport (CVT) method without the addition of transport agents, resulting in well-faceted and thin single crystals with dimensions of ∼20 μm in length and ∼20 nm in height. Thermodynamic calculations were performed to optimize the growth process. The chemical composition and morphology of the nanocrystals were analyzed by energy dispersive X-ray spectroscopy, scanning electron microscopy, and atomic force microscopy. The Rm crystal structure of individual nanocrystals and their high crystalline quality were studied by high-resolution transmission electron microscopy. Magnetotransport measurements confirm that bulk-charge compensation could be achieved by adding a small amount of Se to the ternary compound BiSbTe₃, and the transport properties of thin flakes further reveal the enhanced carrier mobility of topological surface-state carriers.