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    NaBi(MoO4)2 crystal: Defect states and luminescence properties for optoelectronic applications
    (Elsevier, 2025) Isik, M.; Altuntas, G.; Gasanly, N. M.; Darvishov, N. H.
    This paper investigates the electronic and optical properties of NaBi(MoO4)2 crystal through absorbance, thermally stimulated current (TSC), and photoluminescence (PL) measurements. Absorbance analysis revealed important information about the bandgap and the degree of disorder within the material. The bandgap energy of the compound was found to be 2.94 eV. TSC measurements revealed the presence of hole defect centers and provided information regarding charge transport mechanisms. Two TSC peaks were observed at temperatures of 69.3 and 127.5 K, and the activation energies of the trap centers associated with these peaks were found to be 0.05 and 0.14 eV. Two PL peaks were observed around 487 and 536 nm corresponding to the blue and green emissions, respectively. These findings provide a comprehensive understanding the band structure of the NaBi (MoO4)2, highlighting its suitability for use in optoelectronic devices, sensors, and light-emitting applications.
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    Spectroscopic ellipsometry study of linear and nonlinear optical properties of NaBi(Mo0.5W0.5O4)2 crystal
    (Springer, 2024) Isik, M.; Guler, I.; Gasanly, N. M.; Darvishov, N. H.
    In this study, linear and nonlinear optical characteristics of NaBi(Mo0.5W0.5O4)(2) crystal, a new material that may have potential for optoelectronic applications, were investigated. NaBi(Mo0.5W0.5O4)(2) single crystals were grown via the Czochralski method. Two sharp and well-defined peaks were observed in the x-ray diffraction pattern. These peaks were associated with tetragonal crystal structure. The data obtained from ellipsometer measurements was matched with a suitable optical model. This allowed for the presentation of the spectral dependence of various optical parameters like refractive index, dielectric constant, optical conductivity, extinction, and absorption coefficients in the range of 1.2-5.0 eV. As a result of studying the spectral dependence of the absorption coefficient under Tauc relationship, bandgap energy of the compound was found to be 3.20 eV. Using the spectral dependence of the dielectric function, the existence of two critical points with energy values of 3.72 and 4.44 eV was revealed. The change of the refractive index in the region under the bandgap was studied using the single oscillator model. Single oscillator and dispersion energies were determined from the analysis results. Nonlinear optical parameters of NaBi(Mo0.5W0.5O4)(2) crystal were also determined. With this study, the optical properties of the NaBi(Mo0.5W0.5O4)(2) are presented in more detail and valuable information is presented for the potential use of the material in optoelectronic devices.