van der Waals Epitaxy of Bi Nanowires and Bi2Se3 Thin Films on an Antiferromagnetic Substrate of CoNb3S6

The combination of a topological insulator and an antiferromagnet is expected to exhibit the quantum anomalous Hall effect due to the breaking of the time-reversal symmetry. As a layered antiferromagnet, CoNb3S6 was recently found to exhibit an anomalous Hall effect below the Néel temperature (TN = 29 K). Here, we report the controllable growth of Bi nanowires and Bi2Se3 thin films on CoNb3S6 substrates using molecular beam epitaxy. The composition and morphology of the as-prepared Bi nanowires and Bi2Se3 thin films were studied by atomic force microscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy. We found that the as-grown Bi nanowires with abundant sizes are oriented along high-symmetry directions of the substrate, forming firework-like structures. Such firework-like structures of Bi nanowires exhibit a high edge-to-surface ratio as well as a strong anisotropy, highly desirable for photoelectric devices and industrial catalysts. The absence of oxidation peaks verifies that the as-prepared samples are of high quality and air stability, very promising for applications.