Wemple – Didomenico Research Articles

Structural, stoichiometric and optical constants of crystalline undoped lead iodide films prepared by the flash-evaporation method

The flash-evaporation method was used to deposit several thin films (1, 1.2, and 1.35 µm thick) of undoped lead iodide on glass slides held at $$150$$ °C and $$200$$ °C. Their X-ray diffraction patterns, scanning electron microscope micrographs, and energy-dispersive spectroscopy spectra revealed crystalline hexagonal 2H-polytypic structure and high stoichiometry ( $${\text{PbI}}_{x} ;x \cong 1.9$$ ). Their as-measured normal-incidence transmittance $$T_{\text{exp}} (\lambda)$$ –wavelength $$\lambda$$ curves exhibited above a specific wavelength $$\lambda_{{\text{c}}} \approx 520{\text{ nm}}$$ and many well-resolved interference-fringe maxima and minima, indicating good film uniformity. Below $$\lambda_{{\text{c}}}$$ , these $$T_{\text{exp}} (\lambda) - \lambda$$ curves declined sharply toward $$T_{\text{exp}} (\lambda) \cong 0$$ , signifying high film crystallinity. The $$\lambda$$ dependency of optical constants $$n(\lambda)$$ and $$\kappa (\lambda)$$ retrieved from numeric iterative curve fitting of $$T_{\text{exp}} (\lambda) - \lambda$$ data to theoretical $$T_{{{\text{theor}}}} (\lambda)$$ formula describe an air-supported {film/substrate} structure, combined with O’Leary–Johnson–Lim (OJL) interband transition dispersion model and a set of harmonic-like oscillator dispersion formulas. The retrieved bandgap energy $$E_{{\text{g}}}^{{{\text{opt}}}}$$ and band-tail breadth $$\gamma$$ were around $$2.4\,{\text{ eV}}$$ and $$100\,{\text{ meV}}$$ , respectively. The determined $$n(\lambda) - \lambda$$ data gave best curve fits to the Wemple–DiDomenico (WDD) equation with reasonable bandgap energy parameter $$E_{{\text{o}}} \cong 3.8\,{\text{ eV}} \cong 1.6\,E_{{\text{g}}}^{{{\text{opt}}}}$$ , single-oscillator energy strength $$E_{{\text{d}}} \cong 18\,{\text{ eV}}$$ and static index of refraction $$n_{{\text{o}}} \cong 2.4$$ . The calculated optical absorption coefficient $$\alpha (\lambda) = 4{\uppi }\kappa (\lambda)/\lambda$$ was found to obey the direct interband transition with bandgap energy $$E_{{\text{g}}} \cong 2.45\,{\text{ eV}}$$ in the absorption edge region, near which the curve fits of $$\alpha (\lambda)$$ to Urbach formula gave an Urbach tail parameter $${\Gamma }_{{\text{U}}}$$ of $$45\,{\text{ meV}}$$ , consistent with the results of numerical analysis of $$T_{\text{exp}} (\lambda) - \lambda$$ curves. The film thickness and substrate temperature had a slight effect on the determined optical parameters.

The influence of Ar pressure on the structure and optical properties of non-hydrogenated a-Si thin films grown by rf magnetron sputtering onto room-temperature glass substrates

Seven 1.1–1.4-μm-thick hydrogen-free amorphous‑silicon (a-Si) thin films were deposited at high rates (larger than 10 Å/s), by rf magnetron sputtering (RFMS) onto room-temperature glass substrates. The influence of argon-gas pressure on the structural and optical properties of these amorphous films has been systematically studied. We have used the Wemple-DiDomenico (WD) single-effective-oscillator model, n2(ℏω) − 1 = EdE0/(E02 − (ℏω)2), in order to determine the WD parameters oscillator strength or dispersion energy, Ed, and oscillator energy, E0. The amorphous-to-crystalline mass-density ratio, ρa/ρx, in the empirical expression for Ed, proposed by Wemple, is the key factor in understanding the refractive-index behaviour of the RFMS-a-Si thin films. The value of the static refractive index, n(0), which is related to both the atomic structure and mass density, remains approximately constant up to a threshold Ar-gas pressure of nearly 1 Pa, and then it starts dropping rather abruptly. The decrease found in the Urbach energy, EU, as well as the increase observed in the Tauc gap and slope, Eg and B respectively, for Ar-gas pressures higher than the voided-structure threshold sputtering pressure, clearly suggests that the amount of intermediate-range order present within the RFMS-a-Si layers under study, is increasing in direct response to the increase in the Ar-gas pressure, during the deposition process. This is independently corroborated by the decreasing values of the Raman-intensity ratio, ITA/ITO, as the sputtering pressure increases, in the case of high Ar pressure a-Si films.

Structural, DFT, optical dispersion characteristics of novel [DPPA-Zn-MR(Cl)(H2O)] nanostructured thin films

The spin coating technique has been utilized to deposit good adhesion successfully and highly uniform [DPP-Zn(Cl)2(H2O)2], [DPPA-Zn(Cl)2(H2O)2] and [DPPA-Zn-MR(Cl)(H2O)] thin films. The fabricated film thicknesses ranged from 100 to 150 nm. The molecular structure characteristics of compounds have been investigated by FT-IR, 1H NMR, and FAB-Mass spectroscopic. The structural and morphological properties of [DPP-Zn(Cl)2(H2O)2], [DPPA-Zn(Cl)2(H2O)2] and [DPPA-Zn-MR(Cl)(H2O)] thin films were examined by X-ray diffraction (XRD), and scanning electron microscope (SEM), respectively. According to the density functional calculations (DFT) results, the interaction of the zinc complexes conforms to lose associations, the interaction energies for all complexes in the matrix. The bonding mechanism of the zinc complexes includes both σ-dative and π-back bonding components. The measured optical properties of [DPP-Zn(Cl)2(H2O)2], [DPPA-Zn(Cl)2(H2O)2] and [DPPA-Zn-MR(Cl)(H2O)] thin films such as transmittance (T), absorbance (A) and reflectance (R) in UV-vis-NIR spectrum has been used to calculate optical features at room temperatures. The electrophilicity index (ω) of this zinc complexes are ≅ 10.86–13.84. These are significant interesting quantum chemical characteristics. The transparency of the complexes is within the range of ≅ 85–90% in the visible range. The optical band gap (Ego) of [DPP-Zn(Cl)2(H2O)2], [DPPA-Zn(Cl)2(H2O)2] and [DPPA-Zn-MR(Cl)(H2O)] thin films were estimated by DFT and they found to be 1.045, 0937 and 0.736 eV, respectively. The refractive index (n) and the single oscillator energy (Eo) were discussed by the single oscillator Wemple–Didomenico (WD) model. The high accuracy of the novel zinc complexes along with its appropriate optical band gap enabled us to build an efficient visible-blind UV-photodetector, indicating its potential in optoelectronic applications.

Effect of Oxygen Flow Rate on Structural, Electrical and Optical Properties of Zinc Aluminum Oxide Thin Films Deposited by DC Magnetron Sputtering

Zinc Aluminum Oxide thin films were deposited on glass substrates by reactive DC magnetron sputtering method by varying oxygen flow rates from 1 to 4 sccm. Glancing angle X-ray diffraction patterns ofzinc aluminum oxide thin films exhibits (0 0 2) peak with c-plane preferentially oriented parallel to the substrate. The surface morphology and elemental analysis of the films was observed by field emission scanning electron microscopy attached with energy dispersive X-ray analysis spectroscopy. An average optical transmittance of 83–90% is obtained for the films deposited at various oxygen flow rates. The optical band gap of the films increases from 3.41 to 3.53 eV with the increase of oxygen flow rate due to Burstein–Moss effect. The optical dispersion parameters such as dispersion energy (Ed), oscillator energy (Eo) and static refractive index (no) were determined using the Wemple-DiDomenico (W-D) single oscillator model. The nonlinear optical parameters such as optical susceptibility (χ(1)), third order nonlinear optical susceptibility (χ(3)) and nonlinear refractive index (n2) were also determined.

Enhanced optical properties of pure and Sr doped NiO nanostructures: A comprehensive study

We have discussed the detailed optical properties of Ni1-xSrxO (x = 0.0, 0.02, 0.04) nanoparticles calcined at 700 °C which have been synthesized using liquid-solid phase route such as sol-gel method. To discuss the optical behavior, we focus on the reflectance/transmittance spectra of pure and Sr doped NiO samples. Here, we found low reflectance about 15% and high transmittance 41.48% in the visible region which more confirm the high transparency in the visible region. The refractive index n (λ) and extinction coefficient k (λ) spectra of our samples show normal and anomalous dispersion in the range 200–800 nm. In addition, optical dielectric constants, optical conductivity (σ), high frequency dielectric constant using dispersion through both of free carriers and bound carriers, static refractive index (no), Wemple Di-Domenico (WDD) static refractive index (noWDD), ratio of free carrier concentration, effective mass ( Nm*) and plasma frequency (ωp) have been determined. The refractive index dispersive behavior is also examined through WDD single oscillator model and optical dispersion parameters Eo and Ed were calculated using WDD model. Simultaneoulsy, through deconvoluted PL spectra using Gaussian function for all the samples, we found extra green and yellow bands are originate in PL emission spectrum for pure NiO sample and further these bands supressed in Sr doped NiO samples which confirm the reduced defects in the NiO on the Sr doping.

Influences of Mn doping on the microstructural, semiconducting, and optoelectronic properties of HgO nanostructure films

AbstractMn‐doped HgO nanostructured thin films (Hg1‐xMnxO) have been prepared using electron beam evaporation technique on Corning glass (1022) substrate at room temperature with different concentrations x = 0, 0.015, 0.05, 0.1, 0.15, and 0.2. The microstructural, morphological, semiconducting, and optoelectronic properties of the films have been investigated. The X‐ray diffraction spectra suggest a hexagonal wurtzite type structure with lattice parameters decreased with increasing Mn content. It was found that the average particle size of the films decreases with increasing Mn doping which is confirmed by FE‐SEM and AFM micrographs. The optical band gap of the investigated Mn‐doped HgO nanocrystalline films is determined from the absorption coefficient and found to increase with the increase of Mn concentration which is attributed to the sp‐d exchange interaction and/or the quantum confinement effect. The refractive index and extinction coefficient of the Mn‐doped HgO films are also reported. The refractive index dispersion n(λ) is analyzed by single‐effective‐oscillator dispersion model proposed by the Wemple–DiDomenico (WDD). The oscillator parameters were estimated. The obtained dispersion values are suitable for the design of optoelectronic devices.

Physical and optical properties of sprayed Cu2ZnSnS4 (CZTS) thin film: effect of Cu concentration

The crystallographic microstructural and optical properties of CZTS thin film have been investigated with influence of copper concentration in spray solution. The X-ray and Raman study carried out to the prepared CZTS thin films and attained pure kesterite phase. The results of microstructural properties such as crystallite size, d-spacing, microstrain, texture coefficient and standard deviation investigated. The prepared CZTS thin film shows very high optical absorption of the order of 105 cm−1 in the visible region and the optical band gap energy varied between 1.45 and 1.47 eV. This optical band gap tuning is most applicable for solar cells. By using the Wemple–DiDomenico (WDD) single oscillator model, the optical parameters were calculated such as single oscillator energy (E0), dispersion energy (Ed), static refractive index (n0), etc. Large values of optical conductivity (σ) give the promise to the solar cell application.

Effect of oxygen flow rate on structural, electrical and optical properties of zinc aluminum oxide thin films deposited by DC magnetron sputtering -=SUP=-*-=/SUP=-

AbstractZinc Aluminum Oxide thin films were deposited on glass substrates by reactive DC magnetron sputtering method by varying oxygen flow rates from 1 to 4 sccm. Glancing angle X-ray diffraction patterns ofzinc aluminum oxide thin films exhibits (0 0 2) peak with c-plane preferentially oriented parallel to the substrate. The surface morphology and elemental analysis of the films was observed by field emission scanning electron microscopy attached with energy dispersive X-ray analysis spectroscopy. An average optical transmittance of 83–90% is obtained for the films deposited at various oxygen flow rates. The optical band gap of the films increases from 3.41 to 3.53 eV with the increase of oxygen flow rate due to Burstein–Moss effect. The optical dispersion parameters such as dispersion energy ( E _ d ), oscillator energy ( E _ o ) and static refractive index ( n _ o ) were determined using the Wemple-DiDomenico (W-D) single oscillator model. The nonlinear optical parameters such as optical susceptibility (χ^(1)), third order nonlinear optical susceptibility (χ^(3)) and nonlinear refractive index ( n _2) were also determined.

Ellipsometric Investigation of Room Temperature Grown Highly-Oriented Anatase TiO2 Thin Films

In this article, we have reported the structural optimization and optical properties of anatase titanium dioxide (TiO2) thin films grown by direct current magnetron sputtering on a glass substrate at room temperature (RT). The x-ray diffraction measurement revealed anatase phase of TiO2 with preferred orientation (101). The morphological, compositional and topographical properties of the samples are explored by scanning electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy, respectively. The optical properties such as refractive index n, extinction coefficient k and optical bandgap Eg are determined in the broad wavelength range of 246–1688 nm using variable angle spectroscopic ellipsometry accounting for the surface properties in the optical stack model. Moreover, the nonlinear refractive index n2 and the third-order nonlinear optical susceptibility χ(3) are determined using the Tichy–Ticha relation and Wemple–Didomenico (WDD) parameters. The ratio of the carrier concentration to the effective mass N/m* has also been determined. The current research on the optical and dispersion energy parameters of RT grown anatase TiO2 thin films is expected to have a significant impact on advanced flexible optical, optoelectronic, and photonic applications.

Optical and Structural Characterization of TiO-Zn-V Thin Films Synthesized Using the Sol–Gel Method

We report structural and optical properties of thin films grown by the sol–gel method and spin-coating technique. We synthesized thin films of Tiox-Zn-V with varying concentrations of vanadium and titanium. The resulting thin films are characterized by x-ray diffraction (XRD), wavelength-dispersive x-ray fluorescence, and ultraviolet–visible spectrophotometry. XRD results indicate that the majority phase of the resulting structure was Tiox-Zn with a crystallographic plane (020) and an angular position 2θ of 42.38°. The presence of vanadium was confirmed by x-ray fluorescence, and transmittance measurements in the 300–800-nm range showed that the transmittance of this material was over 80%, but reduced in the presence of vanadium. We also found the width of the energy gap to decrease as the concentration of vanadium is increased, thereby suggesting an increase in conductivity and the introduction of a certain amount of disorder into the Tiox-Zn structure according to the Wemple–DiDomenico (WDD) formulation of energy dispersion. Thus, the influence of vanadium on the optical properties of the Tiox-Zn system could be advantageous for the fabrication of smart windows.

Effect of thermal annealing on the structural and optical properties of Cu2FeSnS4 thin films grown by vacuum evaporation method

In this work, the effect of different types of thermal annealing on the properties of Cu2FeSnS4 (CFTS) thin films deposited by thermal evaporation at room temperature on glass substrate were investigated. CFTS powder was synthesized by direct melting of the constituent elements taken in stoichiometry compositions. The X-ray diffraction experimental data indicating that the Cu2FeSnS4 powder illustrating a stannite structure in space group I$$\bar {4}$$2m. From the XRD analysis we have found that the polycrystalline CFTS thin film was only obtained by thermal annealed in sulfur atmosphere under a high vacuum of 400 °C temperature during 2 h. Optical study reveals that the thin films have relatively high absorption coefficients (≈ 105cm−1) and the values of optical band gap energy ranged between 1.38 and 1.48 eV. Other optical parameters were evaluated according to the models of Wemple Di-Domenico and Spitzer-Fan. Finally, hot probe measurements of CFTS thin films reveal p-type conductivity.

Band gap tuning in As40Se53Sb07 thin films by 532 nm laser irradiation: An optical investigation by spectroscopic techniques

The chalcogenide thin films belongs to a special category of important materials due to the unique IR transparency and light induced linear and non linear optical properties change. The optical band gap tuning in thermally evaporated As40Se53Sb07 chalcogenide thin film is being probed under the influence of 532 nm laser illumination. The gradual decrease in transmission and red shift of optical absorption edge with illumination at different time scale is recorded by Fourier transmission infrared spectroscopy. The simultaneous increase in refractive index and absorption coefficient of the illuminated film makes the material as useful candidate for optical switching. The dispersion of refractive index is being analyzed by using Wemple–DiDomenico (WDD) single oscillator model and static refractive index (n0) has also been reported. The exponential decrease of optical band gap with time is attributed to the increase in density of localized states and vacancies. The entire mechanism is explained by the microscopic model in which heteropolar bonds are converted to homopolar ones by the absorption of high energy photons investigated by X-ray photoelectron spectra. The amorphous nature of the studied films was revealed from X-ray diffraction and composition of the film was determined from energy dispersive X-ray analysis. The surface morphology was determined from the scanning electron microscopy. The optical change in absorption coefficient, refractive index, band gap by influence in laser irradiation in such materials may be suitable for optical disc(memory) application for optical time division switch.

Investigation of optical and device parameters of colloidal copper tungsten selenide ternary nanosheets

Hot injection synthesis route has been successfully applied for the preparation of high quality Cu2WSe4 (CWSe) nanosheets in order to determine their optical characterization and device parameters. Several techniques including XRD, SEM, TEM and SAED were used to characterize these nanosheets. These techniques confirmed that Cu2WSe4 nanosheets crystal shapes of synthesized are rectangular and square sheet and the average crystal size is between 20 and 40 nm. The spin coating technique was successfully used to deposit uniform of Cu2WSe4 thin film. Cu2WSe4 thin film has directly transition with a band gap of 1.64 eV. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple–Didomenico (WD) model. The single oscillator energy $$\left( {{E_0}} \right)$$ and the dispersion energy $$\left( {{E_d}} \right)$$ were estimated. Au/Cu2WSe4/n-Si structures was fabricated and its main electrical characteristics described by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of Au/Cu2WSe4/n-Si at room temperature were studied to investigate its basic electrical parameters [i.e. saturation current ( $${I_0}$$ ), ideality factor ( $$n$$ ), barrier height ( $${\Phi _B}$$ ), series ( $${R_s}$$ )]. Structural and optical mechanisms were discussed for future applications in optoelectronic devices.

Synthesis, vibrational and UV–visible studies of sodium cadmium orthophosphate

In this paper, NaCdPO4 orthophosphate was prepared by solid-state reaction technique at high temperature. Structural, vibrational and optical properties have been investigated. X-ray powder diffraction analysis revealed that the titled compound crystallizes in the orthorhombic system with Pmnb space group. Vibrational study by means of Raman and FTIR spectroscopies confirms the existence of the (PO4)3− functional group. Optical properties were recorded at room temperature using UV–visible spectroscopy in the spectral range (200–800) nm. The UV–Vis absorption bands are attributed to the charge transfer from the oxygen ligands to the central phosphate atom inside the PO4 3− groups. The optical absorbance was measured also to determinate the optical band gap using Kubelka–Munk function. The dispersion parameters (E0 and Ed) of this compound were estimated using the Wemple Di-Domenico model.

Influence of Sb addition on the structural and optical characteristics of thermally vacuum evaporated SbxSe1−x thin films

Binary chalcogenide glasses of SbxSe1−x (0.1, 0.2 and 0.3) were synthesized by the conventional melt quenching technique. Thin films of these glasses were deposited by vacuum evaporation technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that, the deposited films have amorphous nature. The optical properties were studied in the wavelength range 200–2500 nm by using Swanepoel method, which is based on the presence of interference fringes. Type of transition in the films is found to be indirect allowed with a value of energy gap decrease with increasing Sb-content due to the increasing of concentration of the localized states. Optical absorption parameters such as Urbach energy, skin depth, steepness, electron-phonon interaction were determined and showed composition dependence. The obtained indirect optical energy gap was found to decrease with increasing Sb-content due to the increasing of concentration of the localized states. In addition, the results indicate that the values of refractive index gradually increase with increasing Sb content which is related. The dispersion characteristics were discussed in terms of the single oscillator expressed by Wemple– Di-Domenico (WD). The obtained dispersion parameters were extracted and showed compositional dependence.

Effect of deposition temperature on the structural and optical properties of CdSe QDs thin films deposited by CBD method

Cadmium selenide quantum dots (CdSe QDs) thin films were deposited onto glass substrates by a chemical bath deposition (CBD) method at different temperatures from an aqueous solution containing l-Cysteine (l-Cys) as capping agent. The evolution of the surface morphology and elemental composition of the CdSe films were studied by AFM, SEM, and EDX analyses. Structural and optical properties of CdSe thin films were investigated by XRD, UV–vis and PL spectroscopy. The dispersion behavior of the refractive index is described using the single oscillator Wemple-DiDomenico (W-D) model, and the physical dispersion parameters are calculated as a function of deposition temperature. The dispersive optical parameters such as average oscillator energy (Eo), dispersion energy (Ed), and static refractive index (no) were found to vary with the deposition temperature. Besides, the electrical free carrier susceptibility (χe) and the carrier concentration of the effective mass ratio (N/m*) were evaluated according to the Spitzer-Fan model.

Improvement of the optoelectronic properties of tin oxide transparent conductive thin films through lanthanum doping

This work highlights some physical investigations on tin oxide thin films doped with different lanthanum content (ratio La–to-Sn = 0–3%). Such doped thin films have been successfully grown by spray pyrolysis onto glass substrates at 450 °C. X-ray diffraction (XRD) patterns showed that SnO2:La thin films were polycrystalline with tetragonal crystal structure. The preferred orientation of crystallites for undoped SnO2 thin film was along (110) plane, whereas La-doped ones have rather preferential orientations along (200) direction. Although the grain size values exhibited a decreasing tendency with increasing doping content confirming the role of La as a grain growth inhibitor, dislocation density and microstrain values showed an increasing tendency. Also, Raman spectroscopy shows the bands corresponding to the tetragonal structure for the entire range of La doping. The same technique confirms the presence of La2O3 as secondary phase. Moreover, SEM images showed a porous architecture with presence of big clusters with different sizes and shapes resulting from the agglomeration of small grains round shaped. Photoluminescence spectra of SnO2:La thin films exhibit a decrease in the emission intensity with La concentration due to the decrease in grain size. Optical transmittance spectra of the films showed high transparency (∼80%) in the visible region. The dispersion of the refractive index is discussed using both Cauchy model and Wemple–Di-Domenico method. The optical band gap values vary slightly with La doping and were found to be around 3.8 eV. It has been found that La doping causes a pronounced decrease in the sheet resistance by up to two orders of magnitude and allows improving the Haacke's figure of merit (Φ) of the sprayed thin films. Moreover, we have introduced for a first time a new figure of merit for qualifying photo-thermal conversion applications. The obtained high conducting and transparent SnO2:La thin films are promising to be useful in various optoelectronic applications.

Structural, linear and nonlinear optical properties of co-doped ZnO thin films

Different compositions of Co-doped zinc oxide [(Zn(1−x)Co x O) (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10)] thin films were evaporated onto highly clean glass substrates by thermal evaporation technique using a modified source. The structural properties investigated by X-ray diffraction revealed hexagonal wurtzite ZnO-type structure. The crystallite size of the films was found to decrease with increasing Co content. The optical characterization of the films has been carried out using spectral transmittance and reflectance obtained in the wavelength range from 300 to 2500 nm. The refractive index has been found to increase with increasing Co content. It was further found that optical energy gap decreases from 3.28 to 3.03 eV with increasing Co content from x = 0 to x = 0.10, respectively. The dispersion of refractive index has been analyzed in terms of Wemple–DiDomenico (WDD) single-oscillator model. The oscillator parameters, the single-oscillator energy (E o), the dispersion energy (E d), and the static refractive index (n 0), were determined. The nonlinear refractive index of the Zn(1−x)Co x O thin films was calculated and revealed well correlation with the linear refractive index and WDD parameters which in turn depend on the density and molar volume of the system.

Study of Se based quaternary Se[sbnd]Pb[sbnd](Bi,Te) chalcogenide thin films for their linear and nonlinear optical properties

Present paper reports the linear and nonlinear optical properties of Se based quaternary SePb(Bi,Te) chalcogenide thin films. The linear optical properties are evaluated with the help of transmission spectra, recorded in the spectral range of 400–2500nm, using an UV–vis–NIR spectrophotometer. The linear refractive index (n) is determined using Swanepoel's method and Tauc extrapolation method is used to determine the optical band gap (Eg). The dispersion of refractive index is analyzed using Wemple–DiDomenico (WDD) single oscillator model and static refractive index (n0) has also been reported. The dielectric constants (ɛ0 and ɛi) and optical conductivity (σ) are determined using linear refractive index (n), extinction coefficient (k) and absorption coefficient (α). Volume energy loss (Vel) and surface energy loss (Sel) are also reported for the investigated materials. The nonlinearity of the system under investigation is studied by empirical and semi empirical relation proposed by various researchers. The formulation proposed by Fournier and Snitzer and Tichy and Ticha is used to determine the nonlinear behavior of refractive index. The third order susceptibility χ(3) is also reported in this paper. All the optical parameters are compared for their behavioral change with the incorporation of Pb additive.

Influence of thickness and annealing on optical constants of Se82.5Te15Sb2.5 chalcogenide thin films

Chalcogenide thin films of Se82.5Te15Sb2.5 with different thickness (50–300 nm) are prepared by thermal evaporation technique. Crystalline phases of the deposited films are identified by x-ray diffraction (XRD). The influence of the film thickness and annealing temperature on the structure is studied by using XRD. The XRD studies show that the crystallinity improved by increasing film thickness and annealing temperature. Furthermore, the particle size and the crystallinity increase whereas dislocation density and strain decrease with increasing both the film thickness and annealing temperature. Transmittance and reflectance of the films are measured in wavelength range 300–2500 nm. It is found that, the optical energy gap, Eg, decreases and the localized state tails, Ee, increases by increasing film thickness and annealing temperature. Dispersion of the refractive index is described using Wemple–DiDomenico (WDD) single oscillator model. Dispersion parameters are calculated as a function of the film thickness and annealing temperature.