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Article Citation - WoS: 22Citation - Scopus: 24Synthesis and Temperature-Tuned Band Gap Characteristics of Magnetron Sputtered Znte Thin Films(Elsevier, 2020) Isik, M.; Gullu, H. H.; Parlak, M.; Gasanly, N. M.Zinc telluride (ZnTe) is one of the attractive semiconducting compounds used in various optoelectronic devices. The usage of ZnTe in optoelectronic applications directs researchers to search its optical characteristics in great detail. For this purpose, structural and optical properties of magnetron sputtered ZnTe thin films were studied by means of x-ray diffraction and transmission spectroscopy measurements. Structural analyses indicated that ZnTe thin films having cubic crystalline structure were successfully grown on soda-lime glass substrates. Transmittance spectra in the 400-1000 nm were recorded in between 10 and 300 K temperature region. The analyses of absorption coefficient spectra resulted in band gap energies decreasing from around 2.31 (10 K) to 2.26 eV (300 K). Temperature dependency of gap energy was studied by Varshni and O'Donnell-Chen relations to determine various optical parameters like absolute zero temperature band gap energy, change of gap energy with temperature, phonon energy.Article Citation - WoS: 7Citation - Scopus: 7Sns2 and Ho-Doped Sns2 Thin Films: Synergistic, Dft, Photocatalytic, and Antibacterial Studies(Elsevier Sci Ltd, 2024) Radja, Imane; Khane, Yasmina; Oliveira, Marisa C.; Longo, Elson; Ribeiro, Renan A. P.; Isik, Mehmit; Khan, Mohammad MansoobThis study investigates Ho-doped tin disulfide (Ho-SnS2) thin films prepared via spray coating, focusing on varying Ho doping levels (0 at. %, 2 at. %, and 4 at. %). Structural analysis through XRD and SEM showcased enhanced crystallinity and morphology in Ho-SnS2 films. Raman and XPS studies provided insight into the film's composition and chemical states. The antibacterial properties of the films were investigated using a bacterial growth inhibition assay. The results showed significant antibacterial activity against Gram-positive and Gram-negative bacteria, highlighting the potential applications of Ho-SnS2 thin films in antibacterial coatings. Ho-SnS2 films exhibited superior photocatalytic activity and antibacterial properties compared to SnS2 films, attributed to efficient charge separation. DFT analysis proposed a mechanism for the antibacterial activity. These findings highlight the efficacy of the spray coating technique in producing Ho-SnS2 films and the potential of Ho-SnS2 films for diverse applications like photocatalysis and antibacterial coatings.Article Citation - WoS: 7Citation - Scopus: 7In situ monitoring of the permanent crystallization, phase transformations and the associated optical and electrical enhancements upon heating of Se thin films(Elsevier Science Bv, 2019) Qasrawi, A. F.; Aloushi, Hadil D.In this work, the in situ structural transformations from amorphous to polycrystalline upon heating and the associated enhancements in the structural parameters of selenium thin films are studied by means of X-ray diffraction technique. The Se thin films which are grown onto ultrasonically cleaned glass substrate by the thermal evaporation technique under vacuum pressure of 10(-5) mbar exhibits structural transformation from amorphous to polycrystalline near 353 K. The films completed the formation of the structure which includes both of the hexagonal and monoclinic phases at 363 K. It is observed that the hexagonal phase dominates over the monoclinic as temperature is raised. Consistently, the thermally assisted crystallization process is accompanied with increase in the crystallite size, decrease in the microstrain, decrease in defect density and decrease in the percentage of stacking faults. The scanning electron microscopy measurements also confirmed the crystallinity of selenium after heating. The time dependent reputations of the crystallization test has shown that the achieved phase transitions and enhancements in structural parameters are permanent in selenium. Optically, the crystallization process is observed to be associated with redshift in the absorption spectra and in the value of the energy band gap. Electrically, the in situ monitoring of the electrical conductivity during the heating cycle has shown that the electrical conductivity stabilizes and exhibit a decrease in the acceptor levels from 566 to 321 meV after the crystallization was achieved.Article Citation - WoS: 10Citation - Scopus: 11Spectroscopic Ellipsometry Investigation of Optical Properties of Β-ga2s3< Single Crystals(Elsevier Science Bv, 2018) Isik, M.; Gasanly, N. M.; Gasanova, L.Ga2S3 single crystals were studied by x-ray diffraction (XRD), energy dispersive spectroscopy and spectroscopic ellipsometry measurements. XRD pattern of the sample is well-matched with reported hexagonal structure of beta-Ga2S3 . The spectra of real and imaginary parts of complex dielectric function (epsilon = epsilon(1) + epsilon(2)) and refractive index (N = n + ik) were plotted in the 1.2-6.2 eV range according to results of ellipsometric data. The e 2 -spectrum and analyses of absorption coefficient pointed out that studied sample has band gap energy of 2.48 eV which is consistent with that of beta-Ga(2)S(3)2. Critical point energies of beta-Ga2S3 were also reported in the present study.Article Citation - WoS: 10Citation - Scopus: 9Structural and temperature-tuned band gap energy characteristics of PbMoO4 single crystals(Elsevier, 2022) Isik, M.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.PbMoO4 is one of the member of the molybdate materials and has been a significant research interest due to its photocatalytic and optoelectronic applications. In the present paper, the structural and optical properties of PbMoO4 single crystals grown by Czochralski technique were investigated. X-ray diffraction pattern presented well-defined and intensive peaks associated with tetragonal scheelite structure. Energy dispersive spectroscopy analyses presented the atomic compositional ratio of constituent elements as consistent with chemical formula of PbMoO4. Raman and infrared transmittance spectra were reported to give information about the vibrational characteristics of the compound. Room temperature transmission spectrum was analyzed by derivative spectroscopy technique and band gap energy was found as 3.07 eV. Temperature-tuned band gap energy characteristics of the single crystal were investigated by performing transmission measurements at different temperatures between 10 and 300 K. The analyses indicated that band gap energy of the PbMoO4 single crystal increases to 3.24 eV when the temperature was decreased to 10 K. Temperature-band gap energy dependency was studied considering Varshni and Bose-Einstein models. The successful fitting processes under the light of applied models presented various optical parameters like absolute zero band gap energy, variation rate of band gap with temperature and Debye temperature.Article Citation - WoS: 3Citation - Scopus: 6Structural and Optical Properties of Thermally Evaporated Cu-Ga (cgs) Thin Films(Elsevier, 2018) Gullu, H. H.; Isik, M.; Gasanly, N. M.The structural and optical properties of thermally evaporated Cu-Ga-S (CGS) thin films were investigated by Xray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and optical transmittance measurements. The effect of annealing temperature on the results of applied techniques was also studied in the present paper. EDS results revealed that each of the elements, Cu, Ga and S are presented in the films and Cu and Ga concentration increases whereas S concentration decreases within the films as annealing temperature is increased. XRD pattern exhibited four diffraction peaks which are well-matched with those of tetragonal CuGaS2 compound. AFM images were recorded to get knowledge about the surface morphology and roughness of deposited thin films. Transmittance measurements were applied in the wavelength region of 300-1000 nm. Analyses of the absorption coefficient derived from transmittance data resulted in presence of three distinct transition regions in each thin films with direct transition type. Crystal-field and spin-orbit splitting energies existing due to valence band splitting were also calculated using quasicubic model.Article Citation - WoS: 4Citation - Scopus: 4Thermally Controlled Band Gap Tuning in Cuo Nano Thin Films for Optoelectronic Applications(indian Assoc Cultivation Science, 2024) Delice, S.; Isik, M.; Gasanly, N. M.Temperature dependency of band gap in CuO nano thin films has been investigated by virtue of transmission experiments at different temperatures. Structural and morphological characterization were achieved using X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Analysis on the XRD diffractogram revealed the presence of monoclinic structure for the CuO. Average crystallite size was determined as 17.8 nm. Absorption characteristics in between 10 and 300 K were presented in the wavelength range of 360-1100 nm. The band gap of the CuO was found to be similar to 2.17 eV at 300 K using Tauc and spectral derivative methods. This value increased to similar to 2.24 eV at 10 K. Both methods showed that the band gap extended with decreasing temperature. Temperature dependency of the band gap was studied using Varshni relation. The band gap at absolute temperature, variation of the band gap with temperature and Debye temperature were calculated as 2.242 +/- 0.002 eV, - 5.4 +/- 0.2 x 10(-4) eV/K and 394 +/- 95 K, respectively.Article Citation - WoS: 12Citation - Scopus: 13Optical and Structural Characteristics of Electrodeposited Cd1-xznx< Nanostructured Thin Films(Elsevier, 2021) Erturk, K.; Isik, M.; Terlemezoglu, M.; Gasanly, N. M.The structural and optical characteristics of Cd1-xZnxS (CdZnS) thin films grown by the electrodeposition method were investigated in the present paper. The crystalline structure of the grown CdZnS thin film was determined as cubic wurtzite due to observed diffraction peaks associated with (111) and (220) planes. Atomic compositional ratios of the constituent elements were obtained using energy dispersive spectroscopy and doping concentration of the Zn was found as 5% (x similar to 0.05). Scanning electron microscopy image of the studied thin film indicated that grown film is nanostructured. Raman spectra of CdS and CdZnS thin films were measured and it was seen that observed longitudinal optical modes for CdZnS present a blue-shift. Temperature-dependent band gap energy characteristics of the thin films were studied performing transmission experiments in the 10-300 K temperature range. The analyses of the recorded transmittance spectra showed that direct band gap energy of the films decreases from 2.56 eV (10 K) to 2.51 eV (300 K) with the increase of temperature. The band gap energy vs. temperature dependency was studied applying well-known Varshni optical model and various optical parameters of the films were reported according to the results of the applied model.Article Citation - WoS: 6Citation - Scopus: 6Linear and Nonlinear Optical Characteristics of Bi12sio20 Single Crystals(Elsevier, 2022) Isik, M.; Gasanly, N. M.Bi12SiO20 single crystals grown by Czochralski method were optically investigated in detail in the present paper. Transmission and reflection measurements were performed at room temperature in the 400-800 nm spectral range on the (111) plane. Linear and nonlinear optical characteristics of the Bi12SiO20 crystal were determined analyzing the transmission and reflection spectra. The spectral dependencies of absorption coefficient, skin depth, refractive index, optical and electrical conductivities, real and imaginary parts of dielectric function were plotted. Analyses of optical parameters presented the direct band gap and Urbach energies as 2.55 and 0.33 eV, respectively. Static refractive index and dielectric constant, oscillator strength, dispersion and single oscillator energies, nonlinear refractive index, first- and third-order nonlinear susceptibilities were revealed. Structural properties of the Bi12SiO20 crystal were investigated by x-ray diffraction and scanning electron microscopy measurements.Article Citation - WoS: 3Citation - Scopus: 4Optical Properties of Cu3in5< Single Crystals by Spectroscopic Ellipsometry(Elsevier Gmbh, 2018) Isik, M.; Nasser, H.; Ahmedova, F.; Guseinov, A.; Gasanly, N. M.Cu3In5S9 single crystals were investigated by structural methods of x-ray diffraction and energy dispersive spectroscopy and optical techniques of ellipsometry and reflection carried out at room temperature. The spectral dependencies of optical constants; dielectric function, refractive index and extinction coefficient, were plotted in the range of 1.2-6.2 eV from ellipsometric data. The spectra of optical constants obtained from ellipsometry analyses and reflectance spectra presented a sharp change around 1.55 and 1.50 eV, respectively, which are associated with band gap energy of the crystal. The critical point (interband transition) energies were also found from the analyses of second-energy derivative of real and imaginary components of dielectric function. The analyses indicated the presence of four critical points at 2.73, 135, 4.04 and 4.98 eV.
