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 TlInS 2 , TlGaS 2 and TlGaSe 2 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.

Temperature‐dependent spectro‐ellipsometric studies of optical transitions near absorption edge of TlInS2

“…In our works [6,7] the accurate values of the refractive index of TlInS 2 were obtained in both orientations, E//C* and E⊥C*(C*: direction normal to the layer plane, E: electrical vector) at room temperature in a range of the photon energies below the energy gap by using spectroscopic ellipsometry and so-called incoherent reflection model [8].…”

Spectroscopic phase modulated ellipsometry in application to some novel single and polycrystalline ternary compounds

“…6 we demonstrate the obtained photon energy dependence of the birefringence for all TlMeX 2 . More details about refractive indices of TlMeX 2 can be found in the work [28]. Here we would like only to mention that fast SPME is an ideal optical technique to study the photo-refraction and its time development in a relaxor state of layered TlMeX 2 [18], as well as to get information on Burns temperature [29] for glassy state of these materials by measuring the effect of residual spontaneous polarization on refractive indices due to quadratic electro-optic effect.…”

Excitation intensity- and temperature-dependent photoluminescence in layered structured Tl2GaInSe2S2 crystals

“…[3][4][5][6][7][8][9][10] It was revealed that the fundamental absorption edge is formed by indirect transitions with band gap energies E gi ¼ 1.98 and 2.06 eV (TlGaSe 2 ) and E gi ¼ 2.27 and 2.44 eV (TlInS 2 ) at T ¼ 300 and 10 K, respectively. 11,12 A high photosensitivity in the visible range, high birefringence in conjunction with a wide transparency range of 0.6-16 lm make these crystals useful for optoelectronic applications.…”