Spitzer Fan Research Articles

Synthesis of Optically Tunable and Thermally Stable PMMA-PVA/CuO NPs Hybrid Nanocomposite Thin Films.

We report the synthesis and comprehensive characterization of polymethylmethacrylate (PMMA)/polyvinylalcohol (PVA) polymeric blend doped with different concentrations of Copper oxide (CuO) nanoparticles (NPs). The PMMA–PVA/CuO nanocomposite hybrid thin films containing wt.% = 0%, 2%, 4%, 8%, and 16% of CuO NPs are deposited on glass substrates via dip-coating technique. Key optical parameters are measured, analyzed, and interpreted. Tauc, Urbach, Spitzer–Fan, and Drude models are employed to calculate the optical bandgap energy (Eg) and the optoelectronic parameters of PMMA–PVA/CuO nanocomposites. The refractive index and Eg of undoped PMMA–PVA are found to be (1.5–1.85) and 4.101 eV, respectively. Incorporation of specific concentrations of CuO NPs into PMMA–PVA blend leads to a considerable decrease in Eg and to an increase of the refractive index. Moreover, Fourier Transform Infrared Spectroscopy (FTIR) transmittance spectra are measured and analyzed for undoped and doped polymeric thin films to pinpoint the major vibrational modes in the spectral range (500 and 4000 cm−1) as well as to elucidate the nature of chemical network bonding. Thermogravimetric analysis (TGA) is conducted under appropriate conditions to ensure the thermal stability of thin films. Doped polymeric thin films are found to be thermally stable below 105 °C. Therefore, controlled tuning of optoelectronic and thermal properties of doped polymeric thin films by introducing an appropriate concentration of inorganic fillers leads to a smart design of scaled multifunctional devices.

Synthesis and characterization of as-grown doped polymerized (PMMA-PVA)/ZnO NPs hybrid thin films

We report the optical, lattice dynamical, and thermal characterization of the poly-methyl-meth-acrylate (PMMA) and poly-vinyl-alcohol (PVA) doped with (wt% = 2%, 4%, 8%, and 16%) of zinc oxide nanoparticles (ZnO NPs) deposited on glass substrate. The optical properties of as-prepared (PMMA-PVA)/ZnO NPs hybrid thin films such as transmittance (T%), reflectance (R%), absorption coefficient (α), optical constants (n and k), and optical dielectric functions (e1 and e2) are deduced using the experimental transmittance and reflectance spectra. Furthermore, a combination of classical models such as Tauc, Urbach, Spitzer–Fan, and Drude models are utilized to calculate the optical and optoelectronic parameters and the band gap of the as-grown nanocomposite thin films. Calculated refractive indices (n) of pure PMMA-PVA polymeric thin films are found to lie in the range (1.5–1.85). We found the optical band gap of PMMA-PVA thin film to be 4.101 eV. Introducing ZnO NPs into PMMA-PVA polymeric matrix leads to a noticeable decrease of the optical band gap. Furthermore, Fourier transform infrared spectroscopy (FTIR) transmittance spectra are measured and interpreted in the spectral range (500–4000 cm−1) to identify the vibrational bands associated with the formation, rotation, and twisting of different bonds. Thermogravimetric analysis (TGA) is performed to test the thermal stability of as-grown thin films. We found that as-grown thin films are thermally stable below 110 °C. Therefore, realistic, scaled and practical devices based on doped polymerized films can be fabricated. Tuning optical, chemical, and thermal properties is of prime importance for the fabrication of state-of-the-art high-tech devices.

Influence of annealing processing on dissipation electrical energy, volume, and surface energy loss functions of CZO films

The present study was conducted to investigate the optical constants of copper (Cu)-doped zinc oxide (ZnO) films annealed at different temperatures. The absorption coefficient of the films increased by changing the annealing temperature. The lattice dielectric constant $$ \varepsilon_{L} $$ , concentration of the free-charge carriers, plasma frequency, Spitzer–Fan model, and the waste heat of electrical energy in the films were analyzed using the refractive index n and extinction coefficient k spectra. The results of the study showed that changing the annealing temperature values significantly influences the refractive index and extinction coefficients of CZO films. The increase in the electrical susceptibility $$ \chi_{c} $$ in annealed films can be due to the increased concentration of free-charge carriers in these films. The maximum electrical energy loss (tan δ) in the films as a function of photon energy occurred at 400 °C. The as-deposited films showed minimum volume and surface energy loss functions in their range of optical band gaps. The variations in the phase and group velocity of the films with post-annealing temperature were consistent with the variations in the reduction of the density of free-charge carriers for these films. Films annealed at 600 °C had the maximum root mean square roughness of about 5.62 nm. Films annealed at 400 °C had the maximum extinction coefficients k such that they increased for all ranges of wavelength. $$ \chi_{c} $$ had the maximum values in the films annealed at 600 °C, for all ranges of wavelength, and they increased by increasing the wavelength. The increase in $$ \chi_{c} $$ of the films annealed at 600 °C can be attributed to the increase in the density of free-charge carriers in these films.

Structural and Optical Properties of Ga2Se3 Crystals by Spectroscopic Ellipsometry

Optical and crystalline structure properties of Ga2Se3 crystals were analyzed utilizing ellipsometry and x-ray diffraction (XRD) experiments, respectively. Components of the complex dielectric function (e = e1 + ie2) and refractive index (N = n + ik) of Ga2Se3 crystals were spectrally plotted from ellipsometric measurements conducted from 1.2 eV to 6.2 eV at 300 K. From the analyses of second-energy derivatives of e1 and e2, interband transition energies (critical points) were determined. Absorption coefficient–photon energy dependency allowed us to achieve a band gap energy of 2.02 eV. Wemple and DiDomenico single effective oscillator and Spitzer–Fan models were accomplished and various optical parameters of the crystal were reported in the present work.

Linear and non linear optical properties of Sb2Se3 thin films elaborated from nano-crystalline mechanically alloyed powder

Sb2Se3 powder is achieved by mechanical milling of Sb and Se elements. X-ray diffraction analysis indicated the formation of Sb2Se3 orthorhombic phase. The latter finding is confirmed by both X-ray photoelectron spectroscopy characterization and Raman spectroscopy. Magnetic measurement revealed the ferromagnetic character of Sb2Se3 powder. Thin films were obtained by thermal deposition using Sb2Se3 powder as a precursor. Optical measurements carried out on thin films showed a high absorption coefficient and a direct band gap of 1.61 eV. The material has then potential application in photovoltaic conversion. Thin film refractive index dispersion (n) obeys Cauchy dispersion equation. n is investigated and found to comply with Wemple–DiDomenico single oscillator dispersion model. The energy E0 of the oscillator and Ed dispersion energy are derived from the refractive index investigation. Spitzer–Fan model exploitation was allowed to derive the high-frequency dielectric constant e∞ and the carrier density N/m* ratio. Additionally, Verdet constant V is determined based on the refractive index dispersion study. Furthermore, the nonlinear susceptibility χ(3) as well as nonlinear refractive index are determined for Sb2Se3 thin films. The nanostructure of the material is likely responsible not only for the high nonlinear characteristics but also for the low magnetic character in Sb2Se3.

Influence of surface topography and annealing temperature on the surface and volume of dissipation electrical energy and Spitzer–Fan model in Al doped ZnO films

The aim of this work is to investigate the optical constants of aluminum doped zinc oxide films annealed at different temperatures. With increasing temperature, due to decreasing unfilled inter-granular volume per unit thickness, the optical transmittance spectra of films were increased. The films have a normal dispersion in the spectral range 400 < λ < 500 nm and the anomalous dispersion in IR range. The lattice dielectric constants eL, the free charge carriers concentration, the plasma frequency, Spitzer–Fan model and the waste of electrical energy as heat of films can be analyzed using the refractive index n and the extinction coefficient k spectra. With increasing annealing temperature, the lattice dielectric constants eL of films decrease however the free charge carriers concentration of films increase. The free carrier electric susceptibility of films annealed at 600 °C has maximum value. The energy loss by the free charge carriers when traversing the bulk and surface of films annealed at 600 °C has a minimum value in the near fundamental absorption edge and it with increasing energy increases.

Synthesis and characterization of zinc-tin-mixed oxides thin films

The mixed oxides thin films were prepared by spray pyrolysis method on glass substrates using different molar ratios of zinc and tin in the starting solution Zn/(Zn + Sn) = 25 at.%, 50 at.%, and 60 at.%. The structural, morphological and optical properties were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Scanning Electron Microscopy (SEM) and spectrophotometry. XRD analysis indicate the coexistence of both the hexagonal phase of ZnO and the tetragonal phase of SnO2 for all mixed thin films. Microstructural parameters such as micro-strain and crystallite size suggest the good crystallinity of mixed thin film at 60 at.%. Optical analysis by means of transmittance T (λ) and reflectance R (λ) measurements allowed us to determine the optical constants for single and mixed oxides. The refractive index dispersion was adequately described by the Wemple-Di-Domenico model. The values of oscillator energy E0, dispersion energy Ed, high-frequency dielectric constant ε∞ as well as the ratio of the carrier concentration to the effective mass N/m∗ were estimated according to both Wemple-Di-Domenico and Spitzer–Fan models.

Insights into the annealing process of sol-gel TiO2 films leading to anatase development: The interrelationship between microstructure and optical properties

The microstructure and optical properties of TiO2 thin films, prepared by the sol-gel dip coating technique on glass substrates, were inspected. After deposition, the films were annealed at several temperatures in the 400–850 °C range and the resulting nanostructured films were studied by different techniques showing that their structural and optical characteristics evolved significantly with the increased annealing temperature. The analysis of these results by the assumption of the Tauc Lorenz model and the use of Wemple–DiDomenico equation leads to a correlation between microstructural aspects and optical characteristics of the films. Thus, crystallization processes (nucleation, growth and phase transformation) and the evolution of films texture and thickness with increasing annealing temperatures are related with the variation of the refractive index, average gap and extinction coefficient during annealing. Finally, the free-carrier concentration in the films, estimated from the Spitzer–Fan model, ranged from 1.44 × 1019 cm−3 to 3.07 × 1019 cm−3 with the changing annealing temperature, which is in agreement with those obtained in similar anatase thin films from electrical measurement techniques.

Electric Susceptibility and Energy Loss Functions of Carbon-Nickel Composite Films at Different Deposition Times

In this work, the optical properties of carbon–nickel films deposited at different deposition times from 50 to 600 sec were investigated. The obtained data of the refractive index n can be analyzed to obtain the high–frequency dielectric constant which describes free carriers and the lattice vibration modes of dispersion. The lattice dielectric constant e L and the plasma frequency ω p at 180 sec have maximum values 10.68 and 79.92x106 Hz, respectively. The free carrier electric susceptibility measurements in the wavelength range (300 – 1000 nm) are discussed according to the Spitzer–Fan model. It is shown that the electric susceptibility at 180 sec has a maximum value and with increasing wavelength it increases. The energy loss by the free charge carriers when traversing the bulk of the films at 180 sec has a maximum value and with increasing wavelength it decreases. The field emission scanning electronic microscopy (FESEM) images were used for estimation of particle size.

Optical Constant and Electrical Resistivity of Annealed Sn3Sb2S6 Thin Films

In this study, we report the annealing effects on the physical properties of Sn3Sb2S6 thin films. Sn3Sb2S6 thin films were prepared onto non-heated glass substrates via thermal evaporation technique. The as-deposited films were annealed in air for 1 h in the temperature range from 100 to 300 °C. X-ray diffraction results show that the crystallinity of the thin films increased after annealing. The microstructure parameters crystallite size, dislocation density, lattice strain and stacking fault probability were calculated. The optical properties were obtained from the analysis of the experimental recorded transmittance and reflectance spectral data over the wavelength range 300–1800 nm. High absorption coefficient (105 cm−1) reached to the visible and near-IR spectral range. A decrease in optical band gap from 1.92 to 1.71 eV by increasing the air annealing temperature was observed. Oscillator energy E o and dispersion energy E d of the films after annealing were estimated according to the model of Wemple–DiDomenico single oscillator. Spitzer–Fan model was applied to determine the electron free carrier susceptibility and the ratio of carrier concentration to the effective mass. The layers annealed at temperatures >150 °C undergo abrupt changes in their electrical properties and exhibit a resistive hysteresis behavior. These properties confer to the material interest perspectives for its application in diverse advanced technologies such as photovoltaic applications and optical storage.

Structural, morphological and optical properties of TiO2:Mn thin films prepared by spray pyrolysis technique

Mn-doped TiO2 thin films were deposited on glass substrates by spray pyrolysis technique at different manganese doping concentrations $$\left( {y = \frac{{\left[ {Mn^{2 + } } \right]}}{{\left[ {Ti^{4 + } } \right]}} = 0, 2, 4, 6\, and\,10\;\% } \right)$$ . X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, spectrophotometry and spectrofluorimetry techniques were used in order to study the effect of Mn doping on the structural, morphological and optical properties of TiO2 thin films. It is found that better film crystallinity was obtained for Mn doping ratio of about 2 at%. Morphological studies revealed that the grown layers exhibited uniform and compact surfaces. An indirect band gap of about 3.44 eV was obtained according to the optical studies. Film thickness, refractive index and extinction coefficient were determined using envelope method. Both Wemple–Di Domenico single oscillator and Spitzer–Fan models were used to study the effect of manganese doping on some optical constants. All photoluminescence spectra showed several emissions in both UV and visible regions.

Comprehensive optical studies on Ga-doped ZnS thin films synthesized by chemical bath deposition

ZnS thin films were prepared by chemical bath deposition on glass substrates using different concentrations of gallium (y=[Ga3+]/[Zn2+]) varying from 0 to 10at% by a step of 2at%. Samples were characterized using X-ray diffraction, spectrophotometric measurements and photoluminescence spectroscopy. The structural studies revealed that the ZnS thin films were poorly crystalline. The level of the residual strain and dislocation seemed to be reduced, respectively, to the values 0.18% and 2.62×109lines.mm−2 for y=6at%. Optical analysis by means of transmittance T(λ) and reflectance R(λ) measurements allowed us to determine the band gap energy value that varied in the range [3.60–3.76]eV, which promoted the use of this material as an optical window or buffer layer in solar cell devices. The refractive index dispersion was adequately described by the Wemple–DiDomenico model. The values of oscillator energy E0, dispersion energy Ed, high-frequency dielectric constant ε∞ as well as the ratio of the carrier concentration to the effective mass N/m* were estimated according to both Wemple–DiDomenico and Spitzer–Fan models. Photoluminescence spectroscopy was performed on ZnS:Ga thin films and the analysis revealed the quenching effect.

Optical characterization of CuIn5S8 crystals by ellipsometry measurements

Optical properties of CuIn5S8 crystals grown by Bridgman method were investigated by ellipsometry measurements. Spectral dependence of optical parameters; real and imaginary parts of the pseudodielectric function, pseudorefractive index, pseudoextinction coefficient, reflectivity and absorption coefficients were obtained from the analysis of ellipsometry experiments performed in the 1.2–6.2eV spectral region. Analysis of spectral dependence of the absorption coefficient revealed the existence of direct band gap transitions with energy 1.53eV. Wemple–DiDomenico and Spitzer–Fan models were used to find the oscillator energy, dispersion energy, zero-frequency refractive index and high-frequency dielectric constant values. Structural properties of the CuIn5S8 crystals were investigated using X-ray diffraction and energy dispersive spectroscopy analysis.

Study of electric susceptibility, electrical resistivity and energy loss functions of carbon–nickel composite films at different annealing temperatures

In this work, the optical and electrical properties of carbon–nickel films annealed at different temperatures (300–1000 °C) were investigated. The obtained data of the refractive index n using the Swanepoel’s method can be analyzed to obtain the high-frequency dielectric constant which describes the free carriers and the lattice vibration modes of dispersion. The lattice dielectric constant ϵL and the plasma frequency ωp at 500 °C have maximum values 4.95 and 40.02 × 106 Hz, respectively. The free carrier electric susceptibility measurements in wavelength range (300–1000 nm) are discussed according to the Spitzer–Fan model. It is shown that the electric susceptibility at 500 °C has maximum value and with increasing wavelength it increases. It is also shown that the waste of electrical energy as heat at 500 °C has maximum value and with increasing wavelength it increases. It is found that energy loss by the free charge carriers when traversing the bulk and surface of films at 800 °C has a minimum value and it is approximately constant with wavelength. It is shown that optical properties were consistent with electrical properties of films annealed at different temperatures in temperature range (15–500 K).

Structural, Optical, and Electrical Properties of SnS:Ag Thin Films

The effect of silver concentration was investigated for doped tin sulfide thin films for which y = [Ag]/[Sn] = 0, 2, 4, 6, 8, and 10 at.%. Structural, morphological, optical, and electrical properties were studied by use of x-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, spectrophotometry, and thermally stimulated current (TSC) spectroscopy. XRD analysis confirmed previous results, i.e. formation of a rocksalt structure with (111) and (200) as preferred orientations. Crystal quality was enhanced when the doping ratio was y = 4 at.%. Addition of silver to the deposited solution did not affect the crystal structure, because no secondary phases related to silver were observed, but it assisted grain growth up to the optimum ratio of 4 at.%. Below 6 at.% interference fringes were observed in transmission and reflection spectra, indicating good surface homogeneity. The optical bandgap energy decreased and the grain size increased when the doping level was y = 4 at.%. The envelope method was applied to the thin film doped at 4 at.%, and dispersion constants were determined by use of the Wemple and Spitzer–Fan models. TSC measurements indicated that the electrical properties at ambient temperature were governed by traps located in the bandgap. From Arrhenius plots, the activation energies of the trap levels were estimated to be approximately 0.28 eV and 1.3 eV.

Effects of Al content on physical properties of ZnS thin films prepared by chemical bath deposition

In this work we report the effect of aluminum on the physical properties of Al-doped ZnS thin films. Our samples have been synthesized by chemical bath deposition from aqueous solutions (Sahraei and Darafarin in Spectrochim Acta A Mol Biomol Spectrosc 149:941–948, 2015). X-ray diffraction analysis revealed that the films are monocrystalline and showed (111) preferred orientation for all the doping concentration. Doping ZnS thin films shows significant changes in the transmittance characteristics in the visible range. The refractive index dispersion and extinction coefficients are adequately described by the Wemple–DiDomenico model. The value of oscillator energy E0, dispersion energy Ed, the high-frequency dielectric constant ɛ∞ and ratio of the carrier concentration to the effective mass N/m* were estimated according to the models of Wemple–DiDomenico and Spitzer–Fan. Photoluminescence behavior of Al-doped ZnS thin films was also studied.

Effect of film thickness on physical properties of RF sputtered In2S3 layers

Indium sulfide (In2S3) layers were deposited by RF magnetron sputtering process with different thickness. The effect of thickness on structural, morphological, optical and photo-conductive properties of the In2S3 layers has been studied. In2S3 layers exhibit near stoichiometric chemical composition and single tetragonal phase with (103) preferred orientation. Variation of surface morphology, Raman bands and optical transmittance of the films have been observed with the increase of film thickness. Energy band gap of the layers determined from transmittance spectra were 2.44–2.66eV (direct) and 1.82–2.06eV (indirect), respectively. Based on the measured optical constants (n and k), the Wemple–DiDomenico model was performed to determine values of single oscillator energy (Eo), dispersion energy (Ed), optical band gap (Eg) and high frequency dielectric constant (ε∞). The determined β parameter indicates In2S3 as an ionic compound. The ε∞ values agree well with that of calculated according to the Spitzer–Fan model. Photoconductivity properties of the films were analyzed relating to the rate competition among photo-generation, recombination and trapping of carriers.

Effect of Sprayed Solution Volume on Physical Properties of Titanium Dioxide Thin Films

Titanium dioxide (TiO2) thin films were deposited on glass substrates by spray pyrolysis technique from different solution volumes. We studied the effect of sprayed solution volume on the structural, morphological and optical properties of TiO2 films. X-ray diffraction studies revealed the presence of an anatase phase with a tetragonal structure with (101) preferred orientation. The best crystallinity was obtained in the case of a sprayed solution volume of 60 ml. Also, this film had a lower average surface roughness (RMS) as measured by atomic force microscopy. Transmission and reflection optical analysis showed interference phenomena indicating a smooth reflecting surface of the film. An indirect band gap of about 3.46 eV was found, indicating a potential use of these films in solar cell devices. Based on the optical measurements, the film thickness was determined by the envelope method, which was in agreement with the scanning electron microscopy result. Wemple–Di Domenico single oscillator and Spitzer–Fan models were used to study the optical constants of the films grown from different sprayed solution volumes. Photoluminescence emission intensity was found to increase with increasing film crystallinity, and the spectra showed ultraviolet and visible emissions corresponding to intrinsic emission and trap levels within the band gap, respectively.

Determination and Analysis of Optical Constant of Annealed Sn2Sb2S5 Thin Films

The effects of annealing on structural, optical and electrical properties of Sn2Sb2S5 thin films were studied. Sn2Sb2S5 thin films were deposited on no-heated glass substrates by single source vacuum evaporation method. The as-deposited films were annealed in air for 1 h at 100, 200 and 300 °C. XRD study shows that annealed films are crystallized according to the preferential orientation (602). Optical measurements show that the thin films have relatively high absorption coefficients in the range of 105–106 cm−1 in the energy range of 2–3.25 eV. It is also found that Sn2Sb2S5 exhibit two optical direct transitions. The models of Wemple–DiDomenico and Spitzer–Fan were applied for the analysis of the dispersion of the refractive index and the determination of the optical and dielectric constants. The electrical resistivity measurements are recorded, and two activation energy values are determined. The layers annealed at 200 and 300 °C exhibit a resistive hysteresis behavior. The properties reported here offer perspective to Sn2Sb2S5 for its application in many advanced technologies.

The effect of substrate temperature on the optical properties of SnSb4S7 thin films

In this work, SnSb4S7 thin films were prepared by vacuum evaporation method, and the effect of substrate temperature on the structural and optical properties were investigated. Substrate temperature was varied from room temperature to 170°C. Optical constants such as band gap, absorption coefficient, extinction coefficient, refractive index, and dielectric constant were determined from the measured transmittance and reflectance spectra in the wavelength range between 300 and 1800nm using the envelope method. The dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple–DiDomenico (W–D) model, and the physical parameters of the refractive index dispersion and the dispersion energy were found. The electrical free carrier susceptibility and the carrier concentration of the effective mass ratio were estimated according to the Spitzer–Fan model. Furthermore, the optical band gap values were calculated by the W–D model and the Tauc model, respectively. The major result of this study is optical, structural, and dielectric properties of SnSb4S7 could be modified with the different substrate temperature.