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The trap centers have a significant impact on the electronic properties of lead tungstate (PbWO4), suggesting their crucial role in optoelectronic applications. In the present study, we investigated and revealed the presence of shallow trap centers in PbWO4 crystals through the utilization of the thermally stimulated current (TSC) method. TSC experiments were performed in the 10–280 K range by applying a constant heating rate. The TSC spectrum showed the presence of a total of four peaks, two of which were overlapped. As a result of analyzing the TSC spectrum using the curve fit method, the activation energies of revealed centers were found as 0.03, 0.11, 0.16, and 0.35 eV. The trapping centers were associated with hole centers according to the comparison of TSC peak intensities recorded by illuminating the opposite polarity contacts. Our findings not only contribute to the fundamental understanding of the charge transport mechanisms in PbWO4 crystals but also hold great promise for enhancing their optoelectronic device performance. The identification and characterization of these shallow trap centers provide valuable insights for optimizing the design and fabrication of future optoelectronic devices based on PbWO4. [ABSTRACT FROM AUTHOR]

This study presents a thorough examination of the structural and thermal characteristics of Bi12SiO20 crystal. X-ray diffraction (XRD) analysis was employed to investigate the crystallographic structure, while scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to ascertain morphological features and elemental composition, respectively. The XRD spectrum exhibited numerous peaks corresponding to the cubic crystalline structure. Thermal behavior was investigated through thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Within the crystal, negligible weight loss was observed up to 750 °C, followed by weight loss processes occurring in the temperature ranges of 750–919 °C and above 919 °C. The 2% weight loss in the range of 750–919 °C was associated with the decomposition process, and the activation energy of this process was found to be 199 kJ/mol considering Coats-Redfern expression. A significant weight loss was observed in the region above 919 oC and was associated with the decomposition of the Bi12SiO20 compound and/or the melting processes of the components of the Bi12SiO20 compound. Three endothermic peaks were observed in the DTA plot. Additionally, DSC measurements conducted under varied heating rates indicated endothermic crystallization process around 348 °C, with an activation energy of 522 kJ/mol determined through the Kissenger equation. These findings present valuable details regarding the crystal's structural configuration, morphological attributes, and decomposition/phase transitions, thereby illuminating its potential applications across various fields. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The compound NaBi(MoO4)2 has garnered significant interest in optoelectronic fields. This study employs spectroscopic ellipsometry to thoroughly examine the linear and nonlinear optical characteristics of NaBi(MoO4)2 crystals, offering detailed insights into their optical behavior. Our investigation presents a precise method for discerning the crystal's spectral features, revealing the spectral variations of key optical parameters such as refractive index, extinction coefficient, dielectric function, and absorption coefficient within the 1.2-5.0 eV range. Through analysis, we determined optical attributes including bandgap energy, critical point energy, and single oscillator parameters. Additionally, we explored the nonlinear optical properties of NaBi(MoO4)2, unveiling potential applications such as optoelectronic devices, frequency conversion, and optical sensors. This study enhances comprehension of optical properties of NaBi(MoO4)2, underscoring its significance in future optical and electronic advancements. [ABSTRACT FROM AUTHOR]

Bi12SiO20 single crystals have attracted interest due to their remarkable photorefractive characteristics. Since bandgap and refractive index are related theoretically to each other, it takes much attention to investigate temperature dependency of bandgap energy to understand the behavior of photorefractive crystals. The present study aims at investigating structural and optical characteristics of photorefractive Bi12SiO20 single crystals grown by the Czochralski method. The structural characterization methods indicated that atomic composition ratios of constituent elements were well-matched with the chemical compound Bi12SiO20, and grown crystals have a cubic crystalline structure. Optical properties of crystals were investigated by room temperature Raman spectroscopy and temperature-dependent transmission measurements between 10 and 300 K. The analyses of transmittance spectra by absorption coefficient and derivative spectrophotometry techniques resulted in energy bandgaps decreasing from 2.61 to 2.48 eV and 2.64 to 2.53 eV as temperature was increased from 10 to 300 K. The Varshni model was applied to analyze temperature-bandgap energy dependency. [ABSTRACT FROM AUTHOR]

GaSe0.75S0.25 having layered structure is a potential semiconductor compound for optoelectronics and two-dimensional materials technologies. Optical and structural measurements of the GaSe0.75S0.25 thin film grown on the glass substrate showed that the compound has hexagonal structure and band energy of 2.34 eV. GaSe0.75S0.25 thin film was also grown on the silicon wafer and p-GaSe0.75S0.25/n-Si heterojunction was obtained. To make the electrical characterization of this diode, temperature-dependent current–voltage (I–V) measurements were carried out between 240 and 360 K. Room temperature ideality factor and barrier height of the device were determined from the analyses of I–V plot as 1.90 and 0.87 eV, respectively. Temperature-dependent plots of these electrical parameters showed that the ideality factor decreases from 2.19 to 1.77, while barrier height increases to 0.94 from 0.71 eV when the temperature was increased from 240 to 360 K. The conduction mechanism in the heterojunction was studied considering the Gaussian distribution due to presence of inhomogeneity in barrier height. The analyses presented the mean zero-bias barrier height, zero-bias standard deviation, and Richardson constant. [ABSTRACT FROM AUTHOR]

In the present paper, we studied linear and nonlinear optical properties of lead molybdate (PbMoO4) single crystals grown by Czochralski method. Raman measurement was performed in the range of 50–1000 cm−1 and 11 active vibration modes were defined in the spectrum. The nature of the observed modes was discussed in detail. Optical absorption of the material was investigated utilizing room temperature transmission and reflection experiments in the spectral range of 360–1000 nm. Spectral changes of absorption coefficient, skin depth, refractive index, optical conductivity, and complex dielectric function of PbMoO4 crystals were studied. Absorption coefficient and optical conductivity exhibited strong increment around 3.0 eV with increasing photon energy. Cut-off wavelength was determined to be 390 nm from the skin depth spectrum. Tauc and derivative spectral analyses revealed the presence of direct bandgap with the energy of 3.05 eV. The static refractive index and dielectric constant were estimated as 2.25 and 5.08, respectively, using Wemple–DiDomenico single oscillator model. Urbach energy was calculated to be 0.071 eV from the exponential dependence of absorption coefficient to photon energy. Dielectric constant increased to 5.42 with energy up to 2.60 eV and then it exhibited decreasing behavior. Second energy derivative analysis of imaginary dielectric function resulted in existence of a critical point at 3.19 eV. First- and third-order nonlinear susceptibilities and nonlinear refractive index were found to be 0.32, 1.9 × 10−12 and 31.7 × 10−12 esu, respectively. These results show that the material may be used in UV filter and sensor applications. [ABSTRACT FROM AUTHOR]

The structural and optical properties of electrodeposited Cd1-xZnxS nanostructured thin films were investigated in the present paper for compositions of x = 0, 0.03, 0.06 and 0.09. X-ray diffraction patterns of the deposited thin films consisted of diffraction peaks related to cubic crystal lattice. The atomic compositional ratios were determined by performing energy dispersive spectroscopy measurements. Scanning electron microscopy images indicated that deposited thin films have nanostructured forms. Raman spectra of the Cd1-xZnxS thin films exhibited two vibrational modes associated with longitudinal optical mode and its first overtone. Transmission measurements were performed on the deposited thin films to get their band gap energies. It was seen from the analyses of absorption coefficient that band gap energy of Cd1-xZnxS thin films increases almost linearly from 2.40 to 2.51 eV as the composition was increased from x = 0 to x = 0.09. [ABSTRACT FROM AUTHOR]

Compositional variation of the band gap energy and refractive index of TlMeX2-type (Me?=?Ga or In and X?=?S or Se) layered mixed crystals have been studied by the transmission and reflection measurements in the wavelength range of 400-1100?nm. The analysis of absorption data of TlGa1-xInxSe2, TlGa(S1-xSex)2, TlGa1-xInxS2, and TlIn(Se1-xSx)2 mixed crystals revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps of mixed crystals decrease at the replacing of gallium atoms by indium and of sulfur atoms by selenium ones. Through the similar replacing of atoms (smaller atoms by larger ones) in the studied mixed crystals, the refractive index shows the quite opposite behavior. [ABSTRACT FROM AUTHOR]

The trap center(s) in Tl2Ga2S3Se single crystals has been investigated from thermoluminescence (TL) measurements in the temperature range of 10-300 K. Curve fitting, initial rise, and peak shape methods were applied to observed TL glow curve to evaluate the activation energy, capture cross section, and attempt-to-escape frequency of the trap center. One trapping center has been revealed with activation energy of 16 meV. Moreover, the characteristics of trap distribution have been studied using an experimental technique based on different illumination temperature. An increase of activation energy from 16 to 58 meV was revealed for the applied illumination temperature range of 10-25 K. [ABSTRACT FROM AUTHOR]

TlGaS2 and TlGaSe2 ternary semiconducting compounds have been of scientific interest due to their large ultrafast optical nonlinearity characteristics. These remarkable properties make them promising semiconducting materials in photonic applications. A series of (TlGaS2)x‒(TlGaSe2)1−x layered mixed crystals grown by Bridgman method were investigated from the standpoint of their Raman spectroscopy characteristics. Experimental Raman scattering study of crystals were reported in the frequency range of 80–400 cm−1 for compositions of x = 0, 0.25, 0.50, 0.75 and 1.0. The effects of crystal disorder on the line-width broadening of Raman-active modes were studied in detail. The asymmetry in the Raman line-shape was analyzed for two highest-frequency intralayer mode presenting two-mode behavior. It was shown that mixed crystal disorder effect is the major source for change of Raman line-shape with composition. [ABSTRACT FROM AUTHOR]

Cu0.5Ag0.5InSe2 (CAIS) thin films were deposited on a glass substrate by sequential sputtering of Cu, Ag, and In2Se3-stacked film layers. Structural characterization showed that the deposited CAIS film satisfies nearly the stoichiometric form with uniform and homogeneous surface structure. The single-phase polycrystalline behavior without any secondary-phase formation was observed from the diffraction profile. The optical properties were investigated using temperature-dependent transmission measurements in the wavelength region of 600–1100 nm and in between 10 and 300 K. In the region of interest, the transmission spectra shifted towards the higher wavelengths as a result of an increase in the sample temperature. The analysis of the absorption data based on the transmission spectra resulted in absorption coefficient values of around 105 cm−1 and the presence of direct allowed optical transition. From the Tauc plots, CAIS samples were found to have three distinct direct optical transitions depending on the possible splitting in the valence band. The obtained room temperature uppermost band gap energy value of 1.09 eV was found in the energy limit of ternary analogues (CuInSe2 and AgInSe2), and also in a good agreement with the previous works in the literature. The dependency of the band gap energy on the temperature was analyzed using fundamental relations. In addition, the electrical characteristics of the film layer were discussed in four-contact conductivity measurements, and room temperature conductivity was observed as 0.8 Ω−1 cm−1. Additionally, two activation energy values were found in the temperature-dependent conductivity profile. As a diode application, CAIS/Si heterojunction was fabricated and the main diode parameters were extracted at dark and room temperature conditions. [ABSTRACT FROM AUTHOR]