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 Ne ' el temperature (T-N = 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 asprepared samples are of high quality and air stability, very promising for applications.