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1The 30th International Conference on Advanced Laser Technologies LS-P-8
ALT'23
Electronic properties of TlFeS2 and TlFeSe2 semiconductors. Theory
and experiment
Z.I. Badalova, Z.A. Jahangirli, E.G. Alizade, T.G. Mammadov, N.A. Abdullayev
Institute of Physics of the Ministry of Science and Education of Azerbaijan, Baku
E-mail: abnadir@mail.ru
We have obtained and characterized by X-ray diffraction, Raman and infrared spectroscopy crystals of TlFeS2 and TlFeSe2 semiconductor compounds [1]. Ab initio calculations of electronic, including optical, properties were carried out on the basis of DFT using the method of full-potential linearized augmented plane waves (FP-LAPW) implemented in the Wien2k code. To experimentally study the optical characteristics of semiconductor compounds TlFeS2 and TlFeSe2, we carried out spectral ellipsometric studies based on determining the change in the polarization of light as a result of its interaction with the surface of crystals upon reflection. The measurements were carried out on an optical range ellipsometer M-2000 DI (J.A. Woollam Co, Inc., US). Figure 1 shows the values of the real Re s (Fig. 1a) and imaginary Im s (Fig. 1b) parts of the dielectric function at different energies for TlFeS2 crystals. Curves 1 and 2 are the theoretically calculated values of the dielectric function for directions along the x and z axes, respectively. Curve 3 is the experimentally determined value of the dielectric function for a polycrystalline sample from ellipsometric measurements. Note the coincidence of critical points (ds/dE = 0) in the dependences s(E). In the TlFeS2 compound, for the real part of the dielectric function (Fig. 1a), this energy is 3.3 eV, and for the imaginary part of the dielectric function, the energies are 2.1, 2.8, and 3.5 eV. The dispersion of the refractive, extinction, and absorption coefficients is also determined. The width of the direct forbidden zone is estimated. Ab initio calculations determine the electronic band structure, the origin of energy states, and projected onto atoms partial densities of states (PDOS).
0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14
Energy, eV Energy, eV
Fig.1. Real (a) and imaginary (b) parts of the dielectric function of TlFeS2: (1, 2) result of theoretical calculation along the crystallographic directions x and z and (3) experimental data.
[1] R.G. Veliyev, N.A. Abdullaev, I.R. Amiraslanov, I.A. Mamedova, D.A. Mamedov, Z.I. Badalova, Sh.K. Qudavasov, S.A. Nemov, Optical Pho-nons in TlFeS2 and TlFeSe2 Semiconductor Compounds, Semiconductors, vol. 56, pp. 32-37, (2022).
