Controlled MOCVD growth of Bi ₂Se ₃ topological insulator nanoribbons

Topological insulators are a new class of materials that support topologically protected electronic surface states. Potential applications of the surface states in low dissipation electronic devices have motivated efforts to create nanoscale samples with large surface-to-volume ratios and highly controlled stoichiometry. Se vacancies in Bi ₂Se ₃ give rise to bulk conduction, which masks the transport properties of the surface states. We have therefore developed a new route for the synthesis of topological insulator nanostructures using metalorganic chemical vapour deposition (MOCVD). MOCVD allows control of the Se/Bi flux ratio during growth. With the aim of rational growth, we vary the Se/Bi flux ratio, growth time, and substrate temperature, and observe morphological changes which indicate a growth regime in which nanoribbon formation is limited by the Bi precursor mass flow. MOCVD growth of Bi ₂Se ₃ nanostructures occurs via a distinct growth mechanism that is nucleated by gold nanoparticles at the base of the nanoribbon. By tuning the reaction conditions, we obtain either single-crystalline ribbons up to 10μm long or thin micron-sized platelets.