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

The Bi 4Se 3 system is an intrinsic superlattice of two topological materials, a 2D Bi 2 sheet and a quintuple layer (QL) slab of Bi 2Se 3. 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 Bi 4Se 3 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 Bi 4Se 3 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.