Atomic scale study of Dirac materials: graphene and topological insulator (Bi2Se3)
Ying Liu
Graphene and topological insulator Bi2Se3 are newly discovered Dirac materials with exotic physical and electronic properties. The molecular beam epitaxy (MBE) and in situ characterization at atomic scale of the materials are demonstrated in this talk[1][2]. Artificial defects of graphene are created by Ar for extending its functions. Their structural, electronic properties and charge state were studied by scanning tunneling microscopy (STM) and q-plus atomic force microscopy (q-plus AFM ), respectively. High quality graphene film provides a good starting surface for growing topological insulator. Due to the weak van de Waals interaction with the substrate, Bi2Se3 grows on graphene in a non-trivial way with pinning and winding. The unique epitaxy forms amount of grain boundaries in the epifilm, leading to local in plane tensile and compressive strains, which modify the Dirac surface states[3]. The discovery provides a unique way for manipulating the surface states of topological insulators, as well as developing novel topological insulator based nanodevices with strain tuning.