Growth of the intrinsic superlattice material Bi4Se3 by DC magnetron sputtering: Layered to faceted growth

Abstract

The Bi4Se3 system is an intrinsic superlattice of two topological materials, a 2D Bi2 sheet and a quintuple layer (QL) slab of Bi2Se3. Both the QL slab and 2D sheet host distinct topologically protected states; this, in turn, allows for the selection of the topologically protected electronic state with the choice of surface layer termination. The Bi4Se3 films were grown by direct current magnetron sputtering under an additional external magnetic field to further confine the plasma region. We developed a recipe to transition from an atomically smooth layered growth to a smooth faceted granular growth. We characterized the morphology, composition, and local crystal orientation of grown films via scanning electron microscopy, energy dispersive x-ray spectroscopy, and electron backscattered diffraction. Additionally, characterization by scanning tunneling microscopy/spectroscopy confirmed the presence of the topologically protected surface states in these films. This work buttresses the commercial scalability of sputtering materials with tunable Bi4Se3 morphology, which provides the option of tuning the surface topological state and thus expanding the possibilities for the production of devices with this material systems.