Semiconductor Physics, Quantum Electronics & Optoelectronics, 27 (3), P. 280-286 (2024).
DOI: https://doi.org/10.15407/spqeo27.03.280


Particularities of optical behavior of Ag8SiS6 single crystal

A.I. Pogodin1*, I.O. Shender1, M.M. Pop1, M.J. Filep1,2, T.O. Malakhovska1, O.P. Kokhan1, V.Yu. Izai3, R. Mariychuk4

1Uzhhorod National University, 46, Pidgirna str., 88000 Uzhhorod, Ukraine
2Ferenc Rákóczi II Transcarpathian Hungarian Institute, Kossuth Sq. 6, 90200 Beregovo, Ukraine
3Comenius University, Mlynska dolina, Bratislava 84248, Slovakia
4University of Presov, 17th November 1, Presov 08116, Slovakia
*Corresponding author e-mail: artempogodin88@gmail.com




Abstract. Ag8SiS6 single crystal was grown by directional crystallization from melt. A crystal sample was investigated by optical ellipsometry and spectroscopy. This sample had nonlinear spectral dependences of the refractive index n and the extinction coefficient k. The presence of a sharp maximum in the spectral dependence of the refractive index and a rather sharp decrease in the values of the extinction coefficient k at the wavelength of 780 nm were found. The behavior of the optical absorption edge of the Ag8SiS6 single crystal in the temperature range of 77…300 K was studied. An exponential dependence of the absorption coefficient α obeying the Urbach rule was observed at all the investigated temperatures. The optical pseudo-gap Eg* and the Urbach energy EU were calculated from the obtained experimental data. An increase in temperature of the Ag8SiS6 crystal was found to lead to a monotonic, almost linear decrease in Eg* (1.853…1.615 eV) and a monotonic nonlinear increase in EU (44.32…55.01 meV). The contributions of the temperature-independent (EU)X,C and temperature-dependent (EU)T components to the total Urbach energy EU for Ag8SiS6 were evaluated within the Einstein model.

Keywords: argyrodite, single crystal, optical absorption edge, Urbach’s rule.

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