Spectroscopic Ellipsometry Investigation of Optical Constants and Dispersion Parameters of TlGaS2 Single Crystals
CRYSTAL RESEARCH AND TECHNOLOGY, cilt.61, sa.8, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 61 Sayı: 8
- Basım Tarihi: 2026
- Doi Numarası: 10.1002/crat.70138
- Dergi Adı: CRYSTAL RESEARCH AND TECHNOLOGY
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Chemical Abstracts Core, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO)
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
Spectroscopic ellipsometry measurements were performed on freshly cleaved layer-plane (001) surfaces of TlGaS2 crystals, with the surface normal approximately oriented along the reciprocal-lattice direction , in the photon-energy range of 1.2-6.2 eV at room temperature. The measured ellipsometric parameters, acquired at a fixed incidence angle and analyzed using ambient-substrate model, were used to determine the dielectric function as well as the effective refractive index and extinction coefficient for the present oblique-reflection configuration. From these effective optical functions, corresponding absorption coefficient, optical penetration depth, and dielectric-related response functions were derived. The derived absorption spectrum exhibits a pronounced absorption-edge feature near 2.43 eV, as identified from the first derivative of the absorption coefficient with respect to photon energy. The low-energy dispersion behavior was analyzed using Wemple-DiDomenico single-oscillator model. In addition, the surface and volume energy-loss functions were evaluated to further characterize the effective electronic response in the measured geometry. The resulting effective optical parameters provide a configuration-specific description of the optical response of TlGaS2, relevant to optoelectronic and photonic applications. Because TlGaS2 is a monoclinic and optically anisotropic crystal, these quantities do not represent the complete intrinsic dielectric tensor or separately resolved polarization-dependent optical constants of the material.