Epitaxial growth of antimony nanofilms on HOPG and thermal desorption to control the film thickness**Project supported by the National Natural Science Foundation of China (Grant Nos. 21622304, 61674045, 11604063, and 61911540074), the National Key Research and Development Program of China (Grant No. 2016YFA0200700), the Strategic Priority Research Program and Key Research Program of Frontier Sciences and Instrument Developing Project (Chinese

Abstract

Group-V elemental nanofilms were predicted to exhibit interesting physical properties such as nontrivial topological properties due to their strong spin–orbit coupling, the quantum confinement, and surface effect. It was reported that the ultrathin Sb nanofilms can undergo a series of topological transitions as a function of the film thickness h: from a topological semimetal (h > 7.8 nm) to a topological insulator (7.8 nm > h > 2.7 nm), then a quantum spin Hall (QSH) phase (2.7 nm > h > 1.0 nm) and a topological trivial semiconductor (h > 1.0 nm). Here, we report a comprehensive investigation on the epitaxial growth of Sb nanofilms on highly oriented pyrolytic graphite (HOPG) substrate and the controllable thermal desorption to achieve their specific thickness. The morphology, thickness, atomic structure, and thermal-strain effect of the Sb nanofilms were characterized by a combination study of scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). The realization of Sb nanofilms with specific thickness paves the way for the further exploring their thickness-dependent topological phase transitions and exotic physical properties.