The bismuth-antimony (Bi-Sb) alloys with some specific Sb concentrations are three-dimensional topological insulators (3D TIs). For the thin Bi-Sb alloy films, the quantum confinement effect can suppress the bulk conduction channels and enhance the transport of the topological surface states. However, the fabrication of Bi-Sb films is still challenging. Here, we have successfully prepared the Bi-Sb alloy films by surface Bi-alloying of the epitaxial Sb nanofilm on highly oriented pyrolytic graphite (HOPG) substrate. The morphology, atomic structure, and electronic structure of the Bi-Sb alloy films were characterized by a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy/spectroscopy (STM/STS). The formation of hexagonal Bi-Sb surface alloy was confirmed by the atomic-resolution STM images. The quantum-well states (QWS) were directly observed in the STS spectra of Bi-Sb films due to the strong quantum confinement effect. The standing-wave patterns of QWS are further observed in the real-space spectra maps. Our work suggests a promising route to fabricate Bi-Sb alloy films and lays the foundation for further exploring their topological electronic structures.

具有某些特定 Sb 浓度的铋锑 (Bi-Sb) 合金是三维拓扑绝缘体 (3D TI)。对于薄的 Bi-Sb 合金薄膜，量子限制效应可以抑制体传导通道并增强拓扑表面态的传输。然而，Bi-Sb 薄膜的制造仍然具有挑战性。在这里，我们通过在高度取向的热解石墨 (HOPG) 衬底上外延 Sb 纳米膜的表面双合金化成功地制备了 Bi-Sb 合金膜。Bi-Sb 合金薄膜的形貌、原子结构和电子结构通过扫描电子显微镜 (SEM)、原子力显微镜 (AFM) 和扫描隧道显微镜/光谱 (STM/STS) 的组合进行表征。原子分辨率 STM 图像证实了六角形 Bi-Sb 表面合金的形成。由于强量子限制效应，在 Bi-Sb 薄膜的 STS 光谱中直接观察到量子阱态 (QWS)。在实空间光谱图中进一步观察到 QWS 的驻波模式。我们的工作为制造 Bi-Sb 合金薄膜提供了一条有前景的途径，并为进一步探索其拓扑电子结构奠定了基础。