Synthesis of semimetal A3Bi (AÂ =Â Na, K) thin films by molecular beam epitaxy

Three-dimensional (3D) Dirac cones are predicted to reside in semimetals A3Bi (A = Na, K). By using molecular beam epitaxy (MBE) and scanning tunneling microscopy (STM), we have successfully established the growth conditions for Na3Bi thin films on Si(1 1 1)-7 × 7, and determined that the lattice of Na3Bi is rotated by 30 degree with respect to that of Si(1 1 1)-7 × 7. The Na3Bi/Si(1 1 1)-7 × 7 thin film was further used as the substrate for the growth of K3Bi. The 3D Dirac-cone-like electronic band structures of Na3Bi and K3Bi have been clearly revealed by angle resolved photoelectron spectroscopy (ARPES).