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Gallium oxide (Ga 2 O 3) nanostructures (NSs) were synthesized via atmospheric pressure chemical vapor deposition (APCVD) technique assisted by hydrogen. The geometrical orientation in terms of the substrate angle was studied to investigate its influence on the morphological, compositional and optical properties of the material. The results revealed that the geometry, stoichiometry and optical parameters of Ga 2 O 3 could be tuned by substrate angle variations during deposition. Tilting the substrate was found to enhance the step coverage of the substrate and the Ga/O atomic ratio above the stoichiometric value. Bandgap of the films was observed to vary inversely (ranged between 4.590 and 4.664eV) to the Ga/O atomic ratio. The refractive index at wavelength of 632.8 nm, dispersion and single oscillator energy of the prepared films were also evaluated, and were found to be in the range of 2.129–3.265, 20.952–56.520eV and 5.309–6.387eV, respectively, with the increase of substrate angle. [ABSTRACT FROM AUTHOR]

The paper considers the modification of the structure and optical properties of chalcogenide films of lead selenide (PbSe) as a result of exposure to a continuous wave (CW) laser with 405 nm wavelength. The mechanisms of oxide layer formation and the accompanying changes in the optical properties of films during laser exposure were considered. Based on the measured reflection and transmission spectra of film regions modified by laser radiation with different exposure times (1–12 s), the extinction coefficient and refractive index were calculated. The study reveals significant modifications in the films' optical constants during the early stages of laser irradiation, leading to oxidation and melting, which are further stabilized by phase transitions. Additionally, temperature field analysis showed that the film's surface temperature in the laser spot's center is strongly influenced by the time-dependent absorption capacity, especially from the 3rd second of exposure onward. [ABSTRACT FROM AUTHOR]

In our investigation, we fabricated high-quality Polyvinyl Alcohol (PVA) films via spin coating on a variety of substrates, with a focus on their potential applications in diverse devices. Through comprehensive characterization techniques, including spectrophotometer measurements, we evaluated the nanostructure and quality of these films. Our analysis revealed a distinct energy gap of 1.74 eV and a significant 5.37 eV direct allowed optical transition, shedding light on the correlation between absorption coefficient and photon energy. Additionally, we meticulously calculated dispersion parameters using the Wemple-DiDomenico relation, obtaining values of 19.1 eV for dispersion energy and 9.48 eV for oscillator energy under the single oscillator model. These results provide further validation of the unique structural characteristics of PVA films. Importantly, our findings underscore the potential of these materials for advanced optoelectronic devices, particularly in the realm of photosensor applications. [ABSTRACT FROM AUTHOR]

In this work, Mn star-shaped structures with 3-fold (3 N) and 4-fold symmetries (4 N) were created on glass substrates. The crystallography of the structures was investigated through X-ray diffraction patterns. The surface morphology and cross-section of the samples were examined using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) images, respectively. The optical spectrum of the structures in the wavelength range of 350–1100 nm was obtained using a single beam spectra photometer. By applying reverse homogenization theory and comparing experimental and theoretical results, the porosity percentage and complex refractive index of the structures were determined. The dielectric constant of the structures was also obtained and analyzed using the real and imaginary parts of the complex refractive index. This investigation revealed that structures with higher porosity exhibited larger grains, a higher refractive index, and a larger dielectric constant. In this work, thin star-shaped layers with different grain sizes and different porosities were prepared., In the investigation of optical properties, it was found that the thin layer with larger grains and higher porosity percentage have a larger refractive index and a larger dielectric constant. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, CeO 2 films incorporating different amounts of Fe (3 %, 5 %, 10 %) were deposited on glass substrates by using the sol-gel method. The physical properties of the films were scrutinized by employing characterization techniques such as X-ray diffractometer (XRD), scanning electron microscopy (SEM) and ultraviolet–visible spectroscopy (UV–vis), respectively. The change of structural parameters was examined using Scherrer, W–H and SSP methods. A decrease in crystallite size was observed with Fe incorporation in all three methods. SEM images presented the homogeneity on the surface increased with increasing Fe doping. Optical measurements showed that the band gap decreased from 3.17 eV to 2.55 eV and at the same time all optical constants decreased with increasing Fe content. These results suggest that the optical properties of CeO 2 films can be tuned by Fe doping. It means that Fe-doped CeO 2 films will play an important role in optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Neodymium doped zinc sulphide (Nd: ZnS) thin films were coated on glass substrates at 450 °C through low cost nebulizer spray pyrolysis (NSP) method. Structure, morphology, opto-electrical characteristics of Nd doped ZnS films with various Nd doping concentrations (0%, 1, %, 3% and 5%) were studied. X-ray diffraction patterns revealed that all coated films were polycrystalline hexagonal structure with (102) as a preferential direction. SEM images showed smooth and uniform spherical grains without any cracks and pinholes. Topological view by AFM described the increasing of roughness of the film through doping concentration. EDAX and Elemental mapping images confirmed the presence of Zn, S and Nd without any other impurities. Raman spectra reveals that E 1 (LO), 2TO, 2LO and 3LO emission modes with corresponding to the wave number. PL spectra showed high intense visible and broad UV emission band at 463 nm and 397 nm, respectively. Thickness of the films increased with Nd doping concentration reflecting the reduction of transparency of the films from 86% to 78% for 0% and 5% of Nd. UV–Vis Spectrum was used to study the energy gap (Eg), dielectric constant(ε), refractive index(n), and extinction coefficient (k) of the prepared films. Four-point probe method was used to calculate the activation energy of Nd: ZnS thin films from the graph drawn between ln (ρ) and (1/T). • Nd:ZnS/glass thin films were coated through low cost nebulizer spray pyrolysis method • SEM mapping and EDX spectra confirm the Nd doped ZnS films with homogeneity. • PL spectra contains intense visible and broad UV emission band at 463 nm and 397 nm, respectively. • High optical transparency was found which is in range from 78 to 86%. • The Ea values are 0.17, 0.13, 0.10 and 0.08 eV, corresponding to 0, 1, 3 and 5% Nd. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) films doped with various concentration (1, 2, 4, 6 wt %) of Methylsilicon (IV) phthalocyanine hydroxide (MeSiPc) were achieved by casting procedure. FTIR results confirmed the increase of disordered ratio within the backbone structure of PVA as the dopant MeSiPc increases. The electrical conductivity versus dopant concentration in the temperature range of 307–392 K was discussed. The linear optical characterizations were studied and three types of interband were observed. Also, some linear optical constants were calculated. The obtained values of the nonlinear constants were increased with the increase of the dopant concentration. Overall, the dopant particles of MeSiPc have a clear impact on the enhancement of the carrier charges mobility, decreasing the width of the band gaps energies and in boosting the molecular polarization of the host material. For these reasons, MeSiPc-PVA matrices are recommended as an excellent candidate material to be exploited in the photo-electronic devices. • PVA films doped with various concentrations of MeSiPc were achieved. • P The increase of MeSiPc ratio causes an increase in the charge carrier mobility. • P PVA-MeSiPc film (6 wt%) could be used as a solar cell due to its low bandgap energy. • P PVA-MeSiPc film is considered as an excellent nonlinear optical material. [ABSTRACT FROM AUTHOR]

A new series of benzobisthiadiazole (BBT)-based donor–acceptor copolymers, namely, PBBT-FT, PBBT-T-FT, and PBBT-Tz-FT, with different π-conjugated bridges have been developed for polymer thin film transistors (TFTs). It was found that inserting different π-conjugated bridges into the backbone of the polymer allowed tailoring of opto-electrical properties, molecular organizations, and accordingly, ambipolar transport of TFTs. Copolymer PBB-T with benzo[1,2-d:4,5-d']bis(thiazole) (BBT) as the accepting unit and benzodithiophene (BDT) as the donor unit is a promising candidate for high-performance non-fullerene polymer solar cells (PSCs). As much as we know the optical and dielectric constants of the PBB-T are not fully known. PBB-T was synthesized and subsequently thin films were properly prepared. By using the Kramers-Kronig relations and the transmission spectra of these thin films, the dielectric and optical constants were calculated and analyzed, including the absorption coefficient, dielectric constant, extinction coefficient, and refractive index of the PBB-T thin films. The results show that these dielectric and optical constants of the PBB-T thin films are quasi-independent on the thicknesses of the thin films, indicating our results are reliable. The features of the dielectric and optical constants show the PBB-T thin films are very promising candidates for high-performance non-fullerene PSCs and potential cut-off filter only permitting red and near-infrared light pass. These results are significant for designing optoelectronic devices related to the PBB-T thin films. Optoelectronic polymer inks are printed to fabricate polymer solar cells. (a) The left panel demonstrates the chemical structures and absorption spectra of the active polymer layer in a typical polymer solar cell. The right panel demonstrates an illustration of the screen-printing process (above) and examples of a laboratory screen printer (bottom left) and an industrial screen printer (bottom right). (b) P3HT:PCBM inks are inkjet-printed to fabricate polymer solar cells. The 3D optical images of the printed polymer features are displayed in the right panel. Image 1 • As much as we know the optical and dielectric constants of the PBB-T are not fully known. PBB-T was synthesized and subsequently thin films were properly prepared. • By using the Kramers-Kronig relations and the transmission spectra of these samples, the optical and dielectric constants were calculated and analyzed, including the absorption, extinction coefficient, dielectric constant and refractive index. • The results show that these optical and dielectric constants of the PBB-T samples are quasi-independent on the thicknesses of the films, indicating our results are reliable.. • The optical and dielectric constants show the PBB-T thin films are very promising candidates for high-performance non-fullerene PSC sand potential cut-off filter only permitting red and near-infrared light pass. [ABSTRACT FROM AUTHOR]

Abstract In this paper we highlight the fabrication of Zinc Telluride (ZT) thin films grown onto glass substrates at 300 °C with varying thickness, in the range of 200 nm–1000 nm, by adopting the simplistic thermal evaporation technique with base pressure of 10−6 m bar. In addition, their structural and optical characterizations are also studied by exploring the influence of substrate annealing temperature and thickness of the samples. The morphology, crystalline nature and composition analysis of the thin films were done by X–ray diffraction and scanning electron microscopy. These results revealed that the sample having thickness around 1000 nm show crystalline nature while the samples having lower thickness demonstrate amorphous structure. The optical characterizations are described in the form of transmission spectra, refractive index, and absorption coefficient. The band gap values obtained by probing optical data, show that all the samples have direct band gaps in the vicinity of 2.25 eV. This suggests possible applications of ZnTe in optoelectronics devices in the visible region of electromagnetic spectra. Highlights • Here is the description of a process for the preparation of graphene oxide in which a little alteration in Hummer's method was done. • In Hummer's method, NaNo3 is used but we have excluded NaNo3 and increased the amount of KMnO4 which resulted in an increase in efficiency of oxidation. • Electrical characterization of sample was accomplished using a complicated ASMEC apparatus to study Capacitance-Voltage (C-V), Current-Voltage (I-V) and Charge Deep-level Transient Spectroscopy investigations. [ABSTRACT FROM AUTHOR]

Abstract Structural and optical properties of 75 mol % Ga 2 Se 3 – 25 mol % Ga 2 S 3 system of single crystals were investigated by experimental techniques of x-ray diffraction (XRD), energy dispersive spectroscopy, Raman spectroscopy and ellipsometry. XRD pattern indicated that the studied compound has crystalline nature with cubic structure. Vibrational modes in the crystal were revealed using Raman spectroscopy experiments in the 90-450 cm−1 frequency range and nine modes were observed in the spectrum. Ellipsometry measurements were utilized in the 1.2–6.2 eV range to get spectral dependencies of optical constants; complex dielectric function, refractive index and extinction coefficient. Under the light of fundamental expressions and models, refractive index and extinction coefficient spectra were analyzed to get various optical parameters of the single crystal. Highlights • Optical properties of (Ga2Se3)0.75 – (Ga2S3)0.25 single crystals were investigated. • Ellipsometry measurements were performed in the 1.2–6.2 eV spectral range. • Spectra of components of complex dielectric function and refractive index were plotted. • Various optical constants of the single crystal were determined. [ABSTRACT FROM AUTHOR]

In this work, a new fluoroborate (B 2 O 3 +AlF 3 +NaF + CaF 2) glass has been fabricated using the melt-quenching technique. Glass sample has been characterized via X-ray diffraction, scanning electron microscope, and optical spectrophotometric measurements for absorption, transmission, and reflection in the range of 350–750 nm. The optical absorption of this transparent glass is used to determine the absorption coefficients, which are then used to estimate the extinction coefficients. The refractive indices as a function of wavelengths are estimated using extinction coefficients and reflectance data of fluoroborate glass. Very important parameters such as density, molar volume, and molar polarizability have been extensively studied. Using these data, fundamental optical parameters such as average oscillator strength (6.42) and inherent absorption wavelength (119 nm) are evaluated using the Drude-Voigt single oscillator model. Compared with previously studied oxide-based glasses, the fluoroborate glass possesses a relatively high refractive index of 1.74 and an Abbe number of 49 in the visible region of 587.6 nm. The relationship between inherent absorption wavelength and Abbe number values is also discussed. Moreover, the values of refractive index and linear optical susceptibility are used to evaluate the third-order optical susceptibility (11.56 × 10−14 esu) and nonlinear refractive index (2.50 × 10−12 esu). These results suggest that fluoroborate glass is a potential material for optical lenses and nonlinear devices in the visible range. [ABSTRACT FROM AUTHOR]

A mixture of sudan yellow 3G dye and poly methyl methacrylate film is fabricated by casting. The optical constants are determined using measurements of absorbance, transmittance, and reflectance spectra. The indirect optical band gap is obtained from Tauc's formula, which is found to be 2 eV. By excitation of the sample with a continuous wave laser beam, the nonlinear optical and the optical limiting properties are studied. The change in refractive index, Δ n , and nonlinear refractive index, n 2 , for the sample is calculated from the diffraction ring patterns and is found to be 44.10 × 10−3 and 18.29 × 10−6 cm2/W respectively. We employ Z-scan to determine nonlinear refractive index n 2 = 0.6 × 10−6 cm2/W and nonlinear absorption coefficient β = 8.79 × 10−3 cm/W. The sample is proven to possess the properties of an optical limiter, as the threshold limiting value of the film is equal to 5.3 mW. [ABSTRACT FROM AUTHOR]

The search for layered structured new semiconductor materials with remarkable optical properties has become a driving force, especially for materials science. Tl 2 In 2 S 3 Se [(TlInS 2) 0.75 (TlInSe 2) 0.25 ], a fascinating compound, holds great promise for advanced photonic and optoelectronic applications. In the present study, the linear and nonlinear optical properties of Tl 2 In 2 S 3 Se layered single crystals were studied by ellipsometry measurements. The variation of refractive index, extinction coefficient, absorption coefficient and skin depth with energy were investigated. Applying the derivative analysis technique to the absorption spectrum, indirect bandgap was found as 2.19 eV. The refractive index data was analyzed considering single-effective-oscillator model. The lattice dielectric constant, plasma frequency, carrier density to the effective mass ratio and zero-frequency refractive index were found. Moreover, the change in optical conductivity with energy yielded to determine the direct bandgap as 2.40 eV. The optical parameters of nonlinear refractive index, first- and third-order nonlinear susceptibilities were also reported. [ABSTRACT FROM AUTHOR]

Using the FP-APW + lo method, the structural, electronic, and optical properties of the Zintl BaAg 2 Te 2 compound were investigated. The calculated unit cell parameters are well matching with the experimental results. In addition, the study of electronic properties reveals that BaAg 2 Te 2 is a semiconductor with a direct bandgap of about 1.445 eV. The optical constants such as loss energy, refractive index, reflectivity, and absorption coefficient have been calculated and analyzed. These constants show a clear anisotropy caused by the different electron polarizability in the x-, y-, and z-directions. Moreover, the direct bandgap and good optical absorption make BaAg 2 Te 2 promising candidates for photovoltaic applications. The thermoelectric properties of the BaAg 2 Te 2 compound in the x, y, and z directions have been studied to obtain the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit (ZT) against temperature and carrier concentrations. Our investigations showed an improvement in the ZT values of BaAg 2 Te 2 with increase in temperature. Moreover, the BaAg 2 Te 2 demonstrated optimal ZT values along the y-axis. [ABSTRACT FROM AUTHOR]

Abstract A theoretical study of the effects of non-resonant intense laser field on the optical response in a Gaussian potential quantum well is performed in the framework of the effective mass approximation. The obtained results indicate that, the depth and range of the considered confinement potential and intense laser field intensity has a significant effect on the optical properties in Gaussian potential quantum wells. Also it was found that the laser field is more effective on the optical response in Gaussian potential quantum wells with smaller range. Highlights • The magnitude of the Absorption Coefficient peak increase with the intense laser field. • The magnitude of the Refractive index changes increase with the intense laser field. • The increase of ILF leads to important effects on the optical properties of GQW. [ABSTRACT FROM AUTHOR]

Ceramic LaFeO 3 (LFO) nanoparticles were synthesized using the solid state reaction method. To grow and study the various optoelectrical parameters of polyvinyl alcohol (PVA) and LFO-PVA nanocomposite films (wt%), the solution casting technique were used. To study optical properties, these films were subjected to Ultraviolet–Visible spectroscopy. From the UV–visible spectra, the high reflectance and low transmittance nature of the sample was observed. The refractive index and extinction coefficient of these films were obtained from reflectance and transmittance data. The optical results reveal that increasing LFO doping concentration decreases the energy band gap (E g) values from 5.20 to 2.74 eV, while Urbach energy (E u) increases from 0.423 eV to 4.871 eV. With doping, the value of single oscillator energy (E o) decreases from 6.212 eV to 3.658 eV, while dispersion energy (E d) increases from 8.481 eV to 158.92 eV. With LFO doping concentration, optical constants and parameters such as refractive index, extinction coefficient, dielectric constants and electron energy loss function were determined from transmittance and reflectance data. The refractive index (n) and extinction coefficient (k) are calculated to be in the ranges from 1.4 to 12 and 5.85 × 10−5 ‒ 26 × 10−3, respectively. The real (ε 1) and imaginary (ε 2) dielectric constants vary from 2 to 138.8 and 3.01 × 10−4 ‒ 3.25 × 10−2, respectively. The volume and surface energy loss functions were determined to be 1.96 × 10−4 ‒ 1.03 × 10−6 and 1.34 × 10−4 ‒ 3.14 × 10−7, respectively. The optical density and skin depth (δ) shows variation with filler concentration (wt%). The maximum optical conductivity σ 1 (ω) and σ 2 (ω) for 48% (wt%) sample were found to be 1.5 × 105 and 1.08 × 109 S−1 at 220 nm. The wavelength dependent real and imaginary parts of the optical dielectric functions and the WDD model were used to calculate the fundamental parameters, including N opt /m*, ε ∞ , τ, μ opt , ω p , ω d , ρ opt , and n 0. The value of N opt /m* was increased from 8.61 × 1052 m3Kg−1 to 5.60 × 1054 m3Kg−1. The reflection loss (RL) and average molar refraction (R m) were found to increase with doping concentration. For these samples, the optical non linear susceptibility (χ(3)) was determined to be in the range from 3.77 × 10−15 to 2.94 × 10−7. The value of electronic polarizability α p decreases from 2.57 × 10−23 to 7.33 × 10−24 for PVA, while for the composite films the value of α p increases from 7.81 × 10−25 to 3.59 × 10−24 in the wavelength range 200–1000 nm. Also, these calculated parameters shows a decreasing trend with LFO doping contents. It was further observed that the investigated parameters exhibit a strong dependence on the LFO doping content. Based on these optoelectronic properties of this material, it could be used for possible optoelectronic applications. • Effect of doping concentration on optoelectrical properties of LaFeO3- polyvinyl alcohol composites films were studied. • The optoelectrical constants of these composites films have been calculated based on the measured transmittance spectra and shows variation with the doping. • The optical band gap and disorder energies with respect to filler concentration in PVA were studied and discussed. • Dielectric properties, Dispersion energy parameters, complex optical conductivity and electronic polarizability were also studied. • The obtained parameters shed light on various physical phenomenonons going in the current system. [ABSTRACT FROM AUTHOR]

Structural and optoelectronic properties of some wurtzite Zn 1- x - y Be x Mg y O quaternary alloys closely lattice-matched to w -ZnO substrate are investigated with density functional theory. The Zn 0·75 Be 0·0625 Mg 0·1875 O, Zn 0·6875 Be 0·0625 Mg 0·25 O and Zn 0·625 Be 0·0625 Mg 0·3125 O alloys having Be/Mg composition ratio in the experimentally prescribed range 2.0–4.0 are considered to achieve high quality stable wurtzite quaternary crystals. Lattice constants (a 0 , c 0) decrease, while direct band-gap (Γ-Γ) increases with increasing Be and Mg composition sum. These optically anisotropic quaternary alloys exhibit diverse optical properties due to electronic transitions from valence O-2p to Be-2p, Be-3s, Zn-5s, Mg-4s, Mg-3p states of conduction band. Calculated optical energy gap, slightly higher than band-gap, shows blue shift with increasing Be and Mg composition sum. Calculated static optical constants ε 1 (0), n (0), R (0) of these alloys reduce with increasing band-gap and vice versa. These quaternary alloys with band-gaps, fundamental absorption edges and optical energy gaps in the UV-A region would have potential applications in fabricating UV-A optoelectronic devices. • Selected w-Zn1-x-yBe x Mg y O/ZnO alloys have Be/Mg content ratio in the range 0.2- 0.4. • Optical features originate from O-2p to Be-2p,3s; Zn-5s,4p; Mg-4s,3p transitions. • Band-gaps (Γ-Γ), fundamental absorption edges & optical gaps lie in the UV-Aregion. • Blue-shift in band-gap & optical energy gap with increasing sum of Be & Mg content. • Selected Zn 1-x-y Be x Mg y O/ZnO alloys are suitable for UV-A optoelectronic devices. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) synthesised via green synthesis using clove extract were incorporated into PEDOT:PSS polymers using the chemical solution deposition technique (CSD), and the effect of surface plasmon resonance in the nanocomposites was investigated. To assess the effect of Silver nanoparticles (AgNPs) (and surface plasmon resonance) on the polymer, TEM, UV–Visible spectroscopy, FTIR, Ellipsometry, and Photoluminescence are used. The surface plasmon peak of the curves in UV–Vis spectroscopy study of these films has shifted towards the infrared region, which may be useful in increasing the efficiency of optical devices. The optical band gap calculated using UV–Vis results reduced from 1.77eV for pure PEDOT: PSS to 1.53eV for the nanocomposite. Ellipsometry data is used to calculate Ψ, Δ values and thickness of films. The Wemple-DiDomenico (WDD) single oscillator model was used to analyse and estimate the dispersion parameters of these films. Refractive indices the films were calculated in the range 1.256–1.643 using the Ellipsometry data. • Conducting Polymer PEDOT: PSS with silver nanoparticles exhibits encouraging optical results. • Wemple – DiDomenico WDD single oscillator model is fitted at visible energy ranges for different films. • Ellipsometry results show a shift towards UV range for polymer metal nanocomposites. • TEM images confirm the size of nanocomposites at 20nm. • Dispersive parameters of PEDOT: PSS thin film are calculated by partial fitting using WDD single oscillator model and Lorentz model. [ABSTRACT FROM AUTHOR]

Pyronin Y dye (PY) is a kind of xanthene derivatives. Thin films of pyronin Y were deposited onto highly cleaned glass substrates using low-cost/spin coating technique. The structure properties of pyronin Y thin films with different thicknesses were investigated by using X-ray diffraction (XRD) and atomic force microscope (AFM). PY thin films for all the studied thicknesses have an amorphous structure supporting the short range order of the grain size. AFM supports the nanostructure with spherical/clusters morphologies of the investigated thin films. The optical constants of pyronin Y thin films for various thicknesses were studied by using UV–vis–NIR spectrophotometer in the wavelength range 350–2500 nm. The transmittance T(λ) , reflectance R(λ) spectral and absorbance ( abs(λ) ) were obtained for all film thicknesses at room temperature and the normal light incident. These films showed a high transmittance in the wide scale wavelengths. For different thicknesses of the studied thin films, the optical band gaps were determined and their values around 2 eV. Real and imaginary dielectric constants, dissipation factor and the nonlinear optical parameters were calculated in the wavelengths to the range 300–2500 nm. The pyronin Y is a new organic semiconductor with a good optical absorption in UV–vis regions and it is suitable for nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Here, we report the doping effect of zinc (Zn) on the physical properties of cadmium oxide (CdO) at various concentrations (1, 2, 3 and 4 wt% of Zn). The studied samples were prepared using sol-gel in addition with sol gel spin coating technique. The structural, optical and dispersive properties were compared with the already reported work in the literature. The structural properties were observed by using atomic force microscopy (AFM). The AFM images show that the grain size decreases with increasing the concentration of Zn. The highest value of average cluster size (78. 71 nm) was found at 1% and the lowest (60.23 nm) when the doping concentration of Zn was 4%. Similar trend was observed in the roughness of the doped thin film when the Zn concentration was increased. The optical properties were examined using Shimadzu UV–Vis–NIR spectrophotometer and we found that the optical band gap of the un-doped CdO and the Zn-doped CdO thin films increases from 2.54 to 2.62 eV as the Zn concentration is increased from 1% to 4%. Also, the optical dispersion parameters ( E o , E d , n 2 ∞ , λ 0 and S o ) were calculated and discussed. We observed that the refractive index dispersion of undoped CdO and the Zn-doped CdO thin films follow the single oscillator model. Finally, spectroscopic method has been exploited to analyze the 3rd order non-linear optical susceptibility χ ( 3 ) and nonlinear refractive index n ( 2 ) . [ABSTRACT FROM AUTHOR]

We have calculated the wavefunctions and energy eigenvalues of spherical quantum dot with infinite potential barrier inside uniform magnetic field. In addition, we have investigated the magnetic field effect on optical transitions between Zeeman energy states. The results are expressed as a function of dot radius, incident photon energy and magnetic field strength. The results present that, in large dot radii, the external magnetic field affects strongly the optical transitions between Zeeman states. In the strong spatial confinement case, energy level is relatively insensitive to the magnetic field, and electron spatial confinement prevails over magnetic confinement. Also, while m varies from −1 to +1, the peak positions of the optical transitions shift toward higher energy (blueshift). [ABSTRACT FROM AUTHOR]

In this research work, manganese antimony sulfide (MnSb 2 S 4) films have been prepared and deposited via the chemical bath deposition route at various thicknesses (189, 275, 329, and 412 nm). The X-ray diffraction results confirmed the polycrystalline character of these films, which exposed orthorhombic structures. The compositional element percentages of these layers were analyzed via energy-dispersive X-ray spectroscopy. The impact of thickness on the optical characteristics of films has also been studied. The optical investigations manifest that these MnSb 2 S 4 films demonstrate a direct optical transition with variable energy gap values (1.77–1.53 eV). The refractive index, optical dielectric constant, absorption coefficient, extinction coefficient, optical conductivity, and others have been estimated and studied. Additionally, the dispersion refractive index, dispersion, and oscillator energies of these spray-deposited films were computed and discussed. In the same way, increasing the thickness of the film has been shown to improve the nonlinear optical parameters. The hot-probe method using a negative voltage was used to investigate the semiconductor behaviour of MnSb 2 S 4 films. It was found that these films tend to behave as p-type semiconductors. This study showed that MnSb 2 S 4 films were utilized as a new absorber layer in photovoltaics. [ABSTRACT FROM AUTHOR]

This research work reports the rigorous studies of the various optical properties of Cadmium containing amorphous thin films (TFs) of multicomponent Se–Te–Sn system. The optical characteristics of prepared TFs are analyzed by using the experimental spectral data of reflection/transmission in the range 4000 Å to 25000 Å. Knowing the spectral variation of the dispersion parameters, we have determined the optical band gap E g o p t and Urbach tail E e. After the addition of Cd, The Urbach energy E e value decreases for the parent Se–Te–Sn sample. The values of the optical bandgap for the present samples are found in the range from 1.24 eV to 1.43 eV with a reversal in trend at x = 4. The indirect optical transition is found in the current study that is confirmed by the transition power factor m. The high dielectric constant (ε ∞), as well as single-oscillator dispersion parameters, are also determined. The dependence of real ε′ and imaginary ε′′ components of optical dielectric constant, relaxation time τ, dissipation factor tan δ , and the optical/electrical conductivities (σ opt and σ ele) on photon energy hν were also studied for multi-components SeTeSnCd (STSC) system. The nonlinear optical characteristics of TFs are examined in terms of their susceptibility and nonlinear refractive index. A discussion has been also discussed about the potential values of the CB- and VB- bands, along with their location. We have observed an excellent agreement between the values of Tauc's constant B determined by Tauc's relation that is obtained by empirical fitting. The present glasses have been found useful for optoelectronic applications after their comparison with different cadmium-containing binary and ternary systems reported by other researchers. [Display omitted] [ABSTRACT FROM AUTHOR]

The organic thin films of fluorescein dye were deposited on fluorine-doped tin oxide glass substrate by using low-cost spin coating technique. The surface of the deposited film was characterized by using AFM and X-ray diffraction spectroscopy, which shows that the film is uniform and amorphous. The spectrophotometric study was carried out at the wavelength range of 300–2500 nm. The spectral dependences of the linear refractive index and absorption index were found to decrease as the wavelength was increased. Tauc's plot study revealed that the film shows the direct transition and energy band gap values were found 1.75 eV and 3.55 eV for the thin film and the substrate, respectively. Optical constants were found nearly the same in the higher energy domain (1.0–4.5 eV). Spectroscopic method was employed to study the nonlinear optical susceptibility χ ( 3 ) . The deposited thin film is a promising optical system for new generation of optoelectronics. [ABSTRACT FROM AUTHOR]

In the current work, the authors present the systematic study on linear and nonlinear optical properties of Copper-phathalocyanine thin film deposited by thermal evaporation system for the first time. The thickness of the prepared thin film was measured and found to be ~300 nm. X-ray diffraction and AFM study confirms that the prepared thin film possess good quality. The orientation of the grown thin film is found to be along (100). UV–vis-NIR study shows that the deposited thin film is highly transparent (>80%) in the wavelength range of 700–2500 nm. Further, the recorded optical data was used to determine the various linear and nonlinear optical parameters. The calculated value of refractive index is found to be in the range of 0.4–1.0. The direct and indirect band gap value is found to be 2.9 and 3.25 eV, respectively. The value of linear and nonlinear susceptibilities is found to be in order of 10 −12 . The higher value of linear and nonlinear parameters makes it suitable for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Single crystal of Tetramethylammonium Tetrachlorozincate has been grown by slow evaporation method. The orthorhombic structure of the material is confirmed by single crystal XRD study. The formation of the material is further supported by Raman study predicting high orientation along ‘ a ’ axis of the crystal. Ferroelectric hysteresis loop gives the evidence for the ferroelectric behaviour of the material. In optical studies, the insulating behaviour of the material is established by Tauc plot obtaining a large value of indirect optical band gap energy which is agreeable with the band gap energy value calculated along ‘ a ’ axis. From the recorded reflectance values, the refractive index and dielectric constant values of the crystal have been calculated. The electronic polarizability also has been calculated using Clausius–Mossotti equation in the high frequency UV–vis–NIR optical region. In addition, the polarizability of the crystal in the lower frequency regions is determined via dielectric studies experimentally, and it is well matched with the theoretically obtained value from Penn analysis. Further, Penn analysis deduces the Plasmon and Fermi energy of the material. [ABSTRACT FROM AUTHOR]

Herein, PbI 2 nanostructured thin films were grown on glass substrates with different (0.5, 1.0 and 1.5 g) solute concentrations using a spin coating technique. The impact of the solute concentration on the structural, optical, nonlinear optical properties was examined thoroughly and was analyzed as a function of solute concentrations. The X-ray diffraction (XRD) patterns of the films confirm a hexagonal wurtzite structure with a preferred orientation along (001) plane. The band gap of the films was calculated using absorbance spectra and found to be about 2.41–2.56 eV. The refractive index (n), extinction coefficient (k), optical dielectric constant, SELF and VELF were investigated and analyzed. In addition, third order optical susceptibility (χ (3) ), nonlinear refractive index (n 2) were also calculated. The obtained data shows that the prepared films are promising for optoelectronics applications. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide (V 2 O 5 ) coatings on quartz and Si(111) substrates are grown by pulsed RF magnetron sputtering technique at constant RF power of 700 W at room temperature. Phase, microstructure and surface morphology are investigated by X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy techniques, respectively. The transmittance and reflectance spectra are recorded for the solar region (200–2300 nm) of the spectral window. Further, optical constants viz. optical band gap, refractive index and extinction coefficient of the deposited V 2 O 5 coatings are estimated. Thickness dependent optical band gaps are found in the range of 2.78–2.59 eV. Wavelength dependent characteristic is also observed both for refractive index and extinction coefficient. Finally, thickness of the present coating predicted theoretically which is matched well with the thickness measured by direct measurement e.g., nanoprofilometry technique. [ABSTRACT FROM AUTHOR]

A sol–gel spin-coating method was used to synthesize N-doped ZnO (NZO) thin films on muscovite mica substrates; the films were then annealed at 200, 300, 400, and 500 °C. The effects of the annealing temperature on their photoluminescence properties and optical constants were investigated. All the films had strong UV emissions in their photoluminescence spectra, but the green emissions at ~2.4 eV were observed only for the annealed films. The average transmittance of all the films was about 80% in the visible range and the absorption edges in the UV range at 375 nm depended strongly on the annealing temperature. The optical band gap of the films decreased gradually as the annealing temperature was increased up to 400 °C, and the Urbach energy decreased significantly as the annealing temperature increased. Finally, the various optical constants, the dielectric constant, and the optical conductivity were measured for the un-annealed film and the film annealed at 500 °C. [ABSTRACT FROM AUTHOR]

The effects of the addition of Ge on the optical and physical properties of a-Pb 15 Se 85-x Ge x (x = 0, 3, 6, 9, 12 at. %) vacuum evaporated thin films are discussed in the given paper. An X-ray diffraction analysis of the films reveals no sharp peaks, indicating their amorphous nature. Transmission spectra of normal incidence were measured in the spectral window of 500 nm–2400 nm. An absorption edge shift has been observed with the addition of Ge at the expense of Se. Swanepoel analysis was applied to compute the refractive index values. Absorption losses were also calculated and discussed. The increase in Ge addition changes the refractive index and absorption coefficient. The bandgap transition is indirect and experimentally calculated using the Tauc-extrapolation method. Penetration depth and optical density were also calculated. WDD model was applied and static refractive index and WDD parameters were evaluated. Theoretical parameters viz. Cohesive energy, average heat of atomization, compactness, polaron radius were also calculated. Efforts were made to correlate obtained optical and physical parameters of the system. • Pb 15 Se 85-x Ge x (x = 0, 3, 6, 9, 12) thermally evaporated thin films were synthesised. • Optical constants and other parameters were studied n and k spectra. • Dielectric constants, energy loss functions and non-linear parameters were studied. • All studied parameters depend strongly upon the photon wavelength and Ge. • The film samples can be used in many IR detectors, sensors and optoelectrical devices. [ABSTRACT FROM AUTHOR]

Abstract: We report a joint experimental and theoretical investigation of optical properties and electronic structure of Er5Si3. Rare-earth alloy optical constants have been measured in the wavelength range , as well as other spectral and electronic characteristics. Spin-polarized calculations of the electronic structure have been performed employing the LSDA+U method accounting for electronic correlations in the 4f shell of Er. All main features of the experimental optical conductivity in the interband region have been well interpreted using the convolution of the calculated densities of states of Er5Si3. [Copyright &y& Elsevier]

Abstract: The optical constants of hydrogenated amorphous silicon (a-Si:H) deposited by plasma enhanced chemical vapor deposition (PECVD) have been obtained using the Forouhi–Bloomer (FB) model and the Tauc–Lorentz (TL) model, respectively. It is indicated that there are some discrepancies between the results derived from the FB model and the TL model. Based on the theory background of the two models, a detailed analysis on these discrepancies has been carried out. Finally, we have proposed a modified FB model to reduce the physical imperfection of the original FB model. This model can better fit the optical constants of a wide variety of amorphous silicon with different microstructures. [Copyright &y& Elsevier]

Abstract: We report on the intersection of spectral dependences of refractive indices n o and n e at the wavelengths 546nm (λ 0) and 450nm (λ 01) in CdGa2Se4 single crystals. The value of difference Δn=n e −n o is equal to zero at the wavelengths involved. When placed between two crossed polarizers, the crystals of CdGa2Se4 exhibit a transmission band at the wavelength of λ 0=546nm (300K). The ground and excited states of three excitonic series (A, B and C) were found out at 13K in CdGa2Se4 crystals, and other parameters of excitons and bands were determined. In the Г point of Brillouin zone the effective mass of electrons m c is equal to 0.14m 0, and the effective masses of holes m v2 and m v3 are equal to 0.76m 0 and 0.94m 0, respectively. The hole mass m v1 depends upon the direction of wave vector k : at polarization E∥c, k ∥a the mass m v1=1.15m 0, and at polarization E∥c, k ∥b m v1=0.84m 0. The values of valence bands splitting in the center of Brillouin zone by the crystal field (Δ cf =49meV) and spin–orbital interaction (Δ so =351meV) were determined. The optical functions n, k, ε 1 and ε 2 in polarizations E⊥c and E∥c for the energy diapason from 3 to 6eV were calculated from the reflectivity spectra by Kramers–Kronig analysis. The evidenced features are discussed on the basis of recent theoretical calculations of the band structure of CdGa2Se4 crystals. [Copyright &y& Elsevier]

Abstract: The spatial dispersion in CdP2 crystals was investigated. The dispersion is positive (n k||с > n k||у ) at λ>λ 0 and negative (n k||с

Abstract: The proposed model is presented to manipulate the dielectric functions of Tauc–Lorentz–Urbach (TLU) model for determining optical constants in some absorbing thin films within the energy range 1.5–3eV. This approach is applicable for strong absorbing thin films that their transmittance decreases with increasing energy in the visible region. In the proposed approach, the exponential function (similar to Urbach tail) is added to the Tauc–Lorentz dielectric function for the energy ranges above energy gap. The presented model provided more accurate estimates of the optical constants in the above band gap region compared to Tauc–Lorentz–Urbach (TLU) or Tauc–Lorentz (TL) model for the investigated strong absorbing thin films. The accuracy of the proposed parametric dielectric function model is verified by the use of some literature data. Also, the validity and applicability of this model is confirmed by the results of the optimization process for retrieving of the optical constants and thickness of thin film by a single transmission spectrum. The results of this approach are in good agreement with the optical constants and thickness of literature data and our experimental data. [Copyright &y& Elsevier]

Abstract: Optical functions n, k, ε 1, ε 2 and d 2 ε 2/dE 2 have been determined from experimental reflection spectra in the region of 1–10eV. The revealed electronic transitions are localized in the Brillouin zone. The magnitude of valence band splitting caused by the spin–orbital interaction Δ SO is lower than the splitting caused by the crystal field Δ CR in the center of Brillouin zone and L and X points. The switching effects are investigated in Zn3P2 crystals. The characteristics of experimental samples with electric switching, adjustable resistors, and time relays based on Zn3P2 are presented. [Copyright &y& Elsevier]

Abstract: Spectroscopic ellipsometry measurements on TlGaSe2, TlGaS2 and TlInS2 layered crystals were carried out on the layer-plane (001) surfaces, which are perpendicular to the optic axis c ⁎, in the 1.2–6.2eV spectral range at room temperature. The real and imaginary parts of the pseudodielectric function as well as pseudorefractive index and pseudoextinction coefficient were found as a result of analysis of ellipsometric data. The structures of critical points in the above-band gap energy range have been characterized from the second derivative spectra of the pseudodielectric function. The analysis revealed four, five and three interband transition structures with critical point energies 2.75, 3.13, 3.72 and 4.45eV (TlGaSe2), 3.03, 3.24, 3.53, 4.20 and 4.83eV (TlGaS2), and 3.50, 3.85 and 4.50eV (TlInS2). For TlGaSe2 crystals, the determined critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure. [Copyright &y& Elsevier]

Abstract: Se100−x Hg x bulk samples have been prepared by conventional melt quenching technique. The thin films of the material have been prepared on glass substrate using the thermal evaporation technique. The transmission spectra has been studied to measure the optical constants like absorption coefficient (α), extinction coefficient (K), optical band gap (E g ), Urbach energy (E e ). The DC conductivity (σ dc) of Se100−x Hg x has been also studied to find the activation energy . The optical band gap increases and Urbach energy first increases then decreases with increase in Hg concentration. DC conductivity and activation energy increases with increase in Hg concentration. These materials are found suitable for the optical disk materials and in optoelectronic devices due to their high absorption coefficient and dependence of reflectance on composition. [Copyright &y& Elsevier]

Abstract: In this work, a poly(o-toluidine) “POT” was synthesized by chemical oxidative polymerization method in aqueous media. High uniform and good adhesion thin films of POT have been successfully deposited by the spin coating technique. The films were characterized by X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectroscopy. The XRD pattern of the POT shows the semi-crystalline nature of the films. FTIR studies show the information of functional groups in POT. The optical transmittance and reflectance of POT film was measured in the 200–2500nm wavelength range. The absorption coefficient analysis shows that the optical band gaps of POT film are direct allowed transition band gaps with 1.2 and 2.6eV. Other optical absorption parameters such as extinction molar coefficient, oscillator strength and electric dipole strength were also calculated. The dispersion parameters were determined and discussed based on the single oscillator model. According to the analysis of dispersion curves some important parameters such as dispersion energy (E d ), oscillator energy (E o ), high frequency dielectric constant ( ε ∞) and lattice dielectric constant (ε L ) were also evaluated. Discussion of the obtained results and their comparison with the previous published data were also given. The obtained desirable results of POT thin film can be useful for the optoelectronic applications. [Copyright &y& Elsevier]

Abstract: The optical properties of Tl2Ga2S3Se layered crystalline semiconductors were investigated from transmission, reflection and ellipsometric measurements. The experimental results of the room temperature transmission and reflection measurements performed in the wavelength range of 400–1100nm showed the presence of both indirect and direct transitions in the band structure of the crystals with 2.38 and 2.62eV band gap energies. Spectroscopic ellipsometry measurements on Tl2Ga2S3Se crystals were carried out on the layer-plane (001) surfaces with light polarization E ⊥ c ⁎ in the 1.20–4.70eV spectral range at room temperature. The real and imaginary parts of the dielectric function as well as refractive and absorption indices were found as a result of analysis of ellipsometric data. The Wemple–DiDomenico single-effective-oscillator model was used to study the dispersion of the refractive index in the below band gap energy range. The structures of critical points have been characterized from the second derivative spectra of the dielectric function. The analysis revealed four interband transition structures with 3.14, 3.40, 3.86 and 4.50eV critical point energies. [Copyright &y& Elsevier]

Abstract: Optical constants, reflectivity response and direct band gap energy (E g d ) were calculated and simulated by developing an electrodynamic-based model for a three medium system, namely vacuum/ferroelectric film/metallic substrate. Depolarization effects due to the contact between the metallic substrate and the FE film, as well as the spatially dependent profile of the dielectric susceptibility enter into the formalism by adapting the phenomenological Landau–Ginzburg–Devonshire theory (LGD). Absorption coefficient is obtained from the Lambert–Beer–Bouguer (LBB) approximation and the direct band gap energy as a function of the characteristic length is calculated by using the general Tauc power law. Numerical simulations lead to range of values for tunable E g d from 2.6 to 2.8eV for characteristic lengths up to 30% the thickness of the film, in concordance with recent reports. [Copyright &y& Elsevier]

Abstract: This article presents a review of several aspects of the characteristic effective medium approximation that has been used to calculate the optical properties of ultrathin multilayer systems treated as one uniform layer with a single set of effective optical constants. The method, applied for normal incidence, enables one to represent any layer stack by one characteristic matrix whose elements are functions of the structure effective optical constants, stack thickness, and wavelength of the incident light wave. The error between values of the optical properties of a layer system calculated by the standard characteristic matrix technique and those calculated by the characteristic effective matrix approximation can be used as a criterion for establishing a limit beyond which the validity of the approximation could be compromised. As part of this grand review, calculations of the optical properties for normal incidence for numerous layer systems that were reported earlier in separate communications, are reviewed and analyzed. [Copyright &y& Elsevier]

Abstract: CuIn3S5 thin films were prepared from powder by thermal evaporation under vacuum (10−6 mbar) onto glass substrates. The glass substrates were heated from 30 to 200°C. The films were characterized for their optical properties using optical measurement techniques (transmittance and reflectance). We have determined the energy and nature of the optical transitions of films. The optical constants of the deposited films were determined in the spectral range 300–1800nm from the analysis of transmission and reflection data. The Swanepoel envelope method was employed on the interference fringes of transmittance patterns for the determination of variation of refractive index with wavelength. Wemple–Di Domenico single oscillator model was applied to determine the optical constants such as oscillator energy E 0 and dispersion energy E d of the films deposited at different substrate temperatures. The electric free carrier susceptibility and the ratio of the carrier concentration to the effective mass were estimated according to the model of Spitzer and Fan. [Copyright &y& Elsevier]

Abstract: This work presents an extension of the characteristic effective medium approximation (CEMA) to ultrathin trilayer systems. The extension has been carried out analytically and is supported by corresponding calculations of the effective optical constants of Cu–Au–Cu and Ag–SiO–Ag trilayer systems using the CEMA approximation. This work is in essence a generalization of the characteristic effective medium approximation introduced earlier for ultrathin bilayer structures. This method is used to derive the effective optical constants of a trilayer system, consisting of three thin layers with each constituent layer of thickness much less than the wavelength of the incident radiation. Within this regime a trilayer system is viewed as one effective layer referred to as an effective stack (ES) with well defined effective optical constants, which can be used to calculate the optical properties of the trilayer stack within a specified wavelength range. The CEMA based calculations of the effective optical constants are applied to two trilayer systems with a total of five stacks. Three are Cu–Au–Cu and two are Ag–SiO–Ag stacks. The thicknesses of the parent layers in the Cu–Au–Cu stack range from 3 to 30nm for Cu and 4 to 40nm for Au; in the Ag–SiO–Ag stack the constituent layers are 6nm for Ag, but range from 5 to 10nm for SiO. This study is for normal or near normal incidence spectroscopy in a wavelength range that extends from visible to near infrared. The agreement between CEMA based ES stack results and those of the standard CMT technique is very satisfactory. [ABSTRACT FROM AUTHOR]

Abstract: FTIR and variable angle spectroscopic ellipsometer in conjunction with computer simulation were employed to investigate the electron beam evaporated SiO x N y thin films. FTIR showed a large absorption band located between 600 and 1250cm−1, which indicates that Si–O and Si–N bands are overlap in SiO x N y films. A three layers model was used to fit the calculated data to the experimental ellipsometric spectra. The main layer was described by Cauchy model while the interface layer and the surface layer were described using Tauc–Lorenz oscillator and Bruggeman effective medium approximation, respectively. The thickness, the refractive index and the extinction coefficient were accurately determined. The refractive index at 630nm was found to increase from 1.74 to 1.85 with increasing the film thickness from 191.6 to 502.2nm. The absorption coefficient was calculated from the obtained extinction coefficient values and it has been used to calculate the Tauc and Urbach energies. [ABSTRACT FROM AUTHOR]

Abstract: Ternary systems of Cd1−x Mn x Te were synthesized by the direct fusion technique. Thin films of these compounds were prepared by an electron beam gun under a vacuum of 10−5 Torr. Structural properties of these compounds in thin film forms were investigated by X-ray diffraction. It was found that these materials crystallize in the zinc-blende form. The optical constants (absorption coefficient and band gap) of the thin films were determined by measuring their reflectance and transmittance in the wavelength region from 500 to 2500nm. Analysis of the optical absorption spectra revealed the existence of one direct energy gap. The energy gap increases as the Mn concentration increases and with decreasing annealing temperatures. The electrical conductivity σ was measured at room temperature and was found to decrease with increasing Mn content. [ABSTRACT FROM AUTHOR]

Abstract: NiO x (x>1) thin films were deposited by reactive DC-magnetron sputtering from a nickel metal target in Ar+O2 with the relative O2 content 5%. The reflectivity and transmission of the films were measured from 350 to 700nm. The films coated to thicknesses of 17, 27 and 34nm had the same absorption mechanism which is a direct allowed transition. The refractive index n and extinction coefficient k of the films were calculated from the measured reflectivity and transmission of these films, and the relationship of the optical band gap with variation in film thickness was studied as well. All results showed that the optical properties of NiO x thin films depended on the film thickness. [ABSTRACT FROM AUTHOR]

Abstract: (PbSe)100−x Cd x thin films of thickness 3000Å with variable concentrations of Cd (x=5, 10, 15 and 20) were prepared by thermal evaporation on glass substrates at room temperature at a base pressure of 10−6 Torr. The structural, optical and electrical properties of these films were studied. X-ray diffraction patterns were used to determine the crystal structure of the films. Films were of polycrystalline texture over the whole range of study. Optical constants of all films were determined by absorbance and reflection measurements in a wavelength range 400–1200nm. Analysis of the optical absorption data showed that the rule of direct transitions predominates. The values of the absorption coefficient (α), extinction coefficient (k) and imaginary part of the dielectric constant were found to increase with increasing Cd content in lead chalcogenides while the refractive index (n) and real part of dielectric constant were increased with increasing Cd concentration up to 15% and then they decreased with 20% of Cd content in PbSe. These results were interpreted in terms of the change in concentration of localized states due to the shift in Fermi level. The dc conductivities and activation energies of the films were measured in the temperature range 298–398K. It was observed that the dc conductivity increases at all temperatures with the increase of Cd content in lead chalcogenide system. The experimental data suggests that the conduction is due to the thermally assisted tunneling of the carriers in the localized states near the band edges. The activation energy and optical band gap were found to decrease with increasing Cd concentration in lead chalcogenide. [Copyright &y& Elsevier]

Abstract: For studying the effect of low doping contents of nickel on physical properties of zinc oxide, four samples of nanofilms with the low ratio Ni/Zn=0%, 0.2%, 0.4% and 0.6% on the glass slide substrates have been prepared by the spin sol–gel technique. The study of the optical and structural analyses on samples shows that initial drying temperature, final annealing temperature and doping percentage of nickel change the optical and structural properties of samples. The structural characterizations showed the zinc oxide structure without other phases or the oxide clusters of nickel and also its low doping concentrations improve the crystalline orientation of the (101) plane of zinc oxide. The formation quality of this direction was increased by increasing low amounts of nickel. The low contents of doping and also by increasing its percentage, there is increase in transparency especially in the ultraviolet region. The calculation of band gap shows a blue shift with doping nickel but decreases by a small quantity with doping more contents. Using the transmittance spectrum, the optical constants were calculated by the pointwise unconstrained minimization algorithm and fitting the data to the Cauchy formula in thin film. [Copyright &y& Elsevier]

Abstract: Different compositions of amorphous Ge20Se80 and Ge20Se75M5 (M=Cd, Bi, or Zn) semiconducting films were deposited onto cleaned glass substrates by thermal evaporation method. The interference transmission spectra T(λ) at normal incidence for Ge20Se75M5 thin films were obtained in the wavelength range 400–2500nm. The direct analysis proposed by Swanepoel that is based on the use of the extremes of the interference fringes was used in order to derive the film thickness and the two parts of the complex refractive index (real part, n, and imaginary part, k,). The dispersion of n is discussed in terms of the Wemple–DiDomenico single-oscillator model. Furthermore, the optical band gap, Eg , has been determined from the absorption coefficient values using Tauc''s procedure. The obtained results of Eg were discussed in terms of the width of localized state Ee . [Copyright &y& Elsevier]