Superconductivity and non-metallicity induced by doping the topological insulators Bi2Se3 and Bi2Te3

We show that by Ca doping the Bi2Se3 topological insulator, the Fermi level can be fine tuned to fall inside the band gap and therefore suppresses the bulk conductivity. Non-metallic Bi2Se3 crystals are obtained. On the other hand, the Bi2Se3 topological insulator can also be induced to become a bulk superconductor, with T-c similar to 3.8 K, by copper intercalation in the van der Waals gaps between the Bi2Se3 layers. Likewise, an as-grown crystal of metallic Bi2Te3 can be turned into a non-metallic crystal by slight variation in the Te content. The Bi2Te3 topological insulator shows small amounts of superconductivity with T-c similar to 5.5 K when reacted with Pd to form materials of the type Pd2Bi2Te3. (C) 2010 Elsevier Ltd. All rights reserved.