Raman scattering and electric conductivity in Bi2(Te0.9Se0.1)3 thin films

High-grade Bi2(Te0.9Se0.1)3 thin films have been obtained and studied by means of confocal Raman spectroscopy and electrical measurements. The annealed films demonstrate the Raman-active modes, A11g(61 cm-1) and E2g(101 cm-1), which were not observed on as-grown samples. At densities of incident laser irradiation above 50 W/mm2, the infrared-active modes, (95 cm-1) and A21u(120 cm-1), emerge in the Raman spectra. The last fact is ascribed to symmetry breaking that is resulting from the internal stress and structural deformations caused by local over-heating. The obtained Bi2(Te0.9Se0.1)3 films manifest dielectric rather than metallic conductivity that is usually observed for bulky crystals of this sort. The variable range hopping conduction has been found to be dominant at temperatures below 100 K. Localization radius and density of localized states at Fermi level have been estimated. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)