Long-wavelength lattice vibrations of Ag3In5Se9 and Ag3In5Te9 single crystals: An inversion of LO- and TO-mode frequencies

HASANLI N.

MODERN PHYSICS LETTERS B, vol.30, no.18, 2016 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 30 Issue: 18
  • Publication Date: 2016
  • Doi Number: 10.1142/s0217984916502298
  • Journal Name: MODERN PHYSICS LETTERS B
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: Semiconductors, chalcogenides, optical properties, infrared reflection, ABSORPTION, SPECTRA
  • Middle East Technical University Affiliated: Yes

Abstract

Infrared (IR) reflectivities are registered in the frequency range of 50-2000 cm(-1) for Ag3In5Se9 and Ag3In5Te9 single crystals grown by Bridgman method. Three infrared active modes are detected in spectra. The optical parameters, real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes (TO and LO modes) and oscillator strength were also determined. The bands detected in infrared spectra were tentatively attributed to various vibration types (valence and valence-deformation). The inversion of LO- and TO-mode frequencies of the sandwiched pair was observed for studied crystals.