Crystal structure and elementary electronic properties of Bi-stabilized α-In2Se3

The introduction of Bias a substitution for In at similar to 12% in In2Se3 stabilizes the alpha-polymorph and facilitates the crystal growth by the modified Bridgeman method. The crystal structure (R-3m, Z = 3, a = 3.9978(8) angstrom, c = 28.276(6) angstrom) and composition, (In0.88Bi0.12)(2)Se-3, of the crystals were determined by single crystal X-ray diffraction. The structure, of the tetradymite type, displays positional disorder within the middle Se layer. Optical measurements indicate that (In0.88Bi0.12)(2)Se-3 has an indirect band gap of about 1.19 eV, shown by electronic structure calculations to be from valence band states near the Gamma point to conduction band states at the L point. Resistivity and Hall effect measurements on Sn-doped crystals of composition (In0.88Bi0.115Sn0.005)(2)Se-3 show it to have a relatively high semiconducting resistivity, about 6 x 10(4) Omega cm at 300 K, with an n-type carrier concentration varying from 10(12)/cm(3) at 300 K to 10(15)/cm(3) at 400 K. (C) 2013 Elsevier Ltd. All rights reserved.