Structure and transport of topological insulators on epitaxial graphene

Recent advancements in spintronics have shown that a class of materials, topological insulators (TI), can be used as a spin-current generator or detector. Topological insulators have protected surface states with the electron’s spin locked to its momentum. To access these surface states, (Bi, Sb)$_{2}$Te$_{3}$ can be grown by molecular beam epitaxy to have the Fermi energy near the Dirac point so that transport occurs only through the spin-dependent surface states. Graphene is another 2D material of great interest for spintronics because of its very long spin diffusion length. This is an ideal material to act as a spin channel in devices. The van der Waals nature of the growth exhibited by 2D materials such as (Bi, Sb)$_{2}$Te$_{3}$ and graphene allows heterostructures to be formed despite the large lattice mismatch. We explore the structure and transport of (Bi, Sb)$_{2}$Te$_{3}$ grown on epitaxial graphene on 6H-SiC substrates for spintronic applications.