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 Γ–M and Γ– K directions. Furthermore, the energy band of Na₃Bi at higher energy is uncovered by doping Cs atoms on the surface.