Optical constants and interband transitions of anisotropic layered structured Tl2GaInS4 crystals by spectroscopic ellipsometry

Spectroscopic ellipsometry measurements were carried out on Tl2GaInS4 layered crystals for orientations of electric field vector, parallel (E//c∗) and perpendicular (E⊥c∗) to optical axis c∗. The measurements were performed in the 1.2–6.2 eV spectral range at room temperature. The real and imaginary components of the pseudodielectric function, pseudorefractive index and pseudoextinction coefficient were calculated from the analysis of ellipsometric data. The energies of interband transitions (critical points) have been found from the least-square fitting of the second derivative spectra of the pseudodielectric function. The results indicated five each interband transition structures for E//c∗ and E⊥c∗ configurations. The obtained critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure given in literature.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Ellipsometry measurements were carried out in the 1.2–6.2 eV spectral range. ► Anisotropic behavior of the optical properties of Tl2GaInS4 crystal was studied. ► Spectral dependence of optical constants n and k were obtained. ► Second derivative spectra of dielectric function revealed interband transitions.