Optical constants at and below energy gap of layered ternary Tl compounds

Abstract

Incoherent reflection mode of spectroscopic phase modulated ellipsometry (SPME) was firstly applied to quasi-two-dimensional TlInS2, TlGaS2 and TlGaSe2 to obtain uniaxial optical anisotropy of these materials at room temperature. Simulation of the measured SPME signal was performed within uniaxial incoherent reflection model, with a result of perfect match to experimental data for all three compounds. Birefringence in a photon energy range from below the energy gap of each material and down to 0.76eV was reliably determined. Obtained birefringence agrees well with optical anisotropy reported earlier from light figure studies of the above materials in the visible spectral range. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)