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Optical properties of thin films from new chalcogenide GeSe2-Sb2Se3-PbTe glasses

K. PETKOV1,* , J. TASSEVA1, V. VASSILEVa1, L. ALJIHMANI2

Affiliation

  1. Institute of Optical Materials and Technologies “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 109, 1113 Sofia, Bulgaria
  2. Department of Semiconductors, University of Chemical Technology and Metallurgy, 8 Kl. Ohridsky Blvd, 1756 Sofia, Bulgaria

Abstract

Thin GeSe2–Sb2Se3–PbTe films with controllable composition were deposited by thermal evaporation. Their optical properties are studied as a function of the PbTe content and at different GeSe2/Sb2Se3 ratio. The optical constants (refractive index, n and absorption coefficient, α) and thickness, d as well as the optical band gap, Eg, depending on the PbTe content are derived from the transmission and reflection spectra measured in the region 500-2500 nm applying the Swanepoel’s envelop method and Tauc’s procedure. With the increase of PbTe content in the layers, the absorption edge is shifted to the longer wavelengths, i.e. lower energies - from 1.52 eV for (GeSe2)80(Sb2Se3)20 to1.14 eV for (GeSe2)48(Sb2Se3)12(PbTe)40, the refractive index increases while the optical band gap decreases. Similar dependence was observed with the increase of Sb2Se3 content in the layers with 10 at. % PbTe. A correlation between the optical band gap and the composition of the thin films from the studied system could be seen. These results indicate an increase of the bond’s stronger metal character and probable formation of a complicated band gap structure..

Keywords

Thin films, Chalcogenide glasses, Optical properties, IR spectroscopy.

Submitted at: June 14, 2011
Accepted at: Nov. 23, 2011

Citation

K. PETKOV, J. TASSEVA, V. VASSILEVa, L. ALJIHMANI, Optical properties of thin films from new chalcogenide GeSe2-Sb2Se3-PbTe glasses, Journal of Optoelectronics and Advanced Materials Vol. 13, Iss. 11-12, pp. 1514-1518 (2011)