Semimetal Na3Bi Thin Film Grown on Double-Layer Graphene by Molecular Beam Epitaxy

Atomically flat thin films of topological semimetal Na3Bi are grown on double-layer graphene formed on 6H-SiC(0001) substrates by molecular beam epitaxy. By combined techniques of molecular beam epitaxy, scanning tunneling microscopy and angle resolved photoelectron spectroscopy, the growth conditions for Na3Bi thin films on double-layer graphene are successfully established. The band structure of Na3Bi grown on graphene is mapped along (Gamma) over bar-(M) over bar and (Gamma) over bar-(K) over bar directions. Furthermore, the energy band of Na3Bi at higher energy is uncovered by doping Cs atoms on the surface.