  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 suppress 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 Tc ~ 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 of the Te
content. The Bi2Te3 topological insulator shows small amounts of
superconductivity with Tc ~ 5.5 K when reacted with Pd to form materials of the
type PdxBi2Te3.
