Optical Transmittance Studies Research Articles

Second harmonic generation of fluorine-doped zinc oxide thin films grown on soda-lime glass substrates by a chemical spray technique

Second harmonic generation (SHG) studies of fluorine-doped zinc oxide (ZnO:F) thin films deposited on soda-lime glass substrates from an aged solution in conjunction with zinc pentanedionate, using the chemical spray deposition technique were carried out. The χ31(2) and χ33(2) independent tensorial components of the quadratic nonlinear optical susceptibility of the ZnO:F thin films were evaluated. Scanning electron microscopy and X-ray diffraction investigations revealed a homogeneous distribution of nanoparticles of similar size and morphology for various samples deposited at different substrate temperatures (ranging from 400 to 525°C). The SHG-technique revealed a clear dependence of the nonlinear optical response with the deposition temperature. Typical optical transmittance and photoluminescence (PL) studies were also performed, from which a bandgap (Eg) of 3.3eV was evaluated in films deposited under optimal conditions of conductivity and transmittance.

Vibrational spectroscopic studies of an organic non-linear optical crystal 8-hydroxyquinolinium picrate

8-Hydroxyquinolinium picrate (8-HQP) was synthesized by the addition of equimolar quantities of 8-hydroxyquinoline (8-HQ) and picric acid (PA). Single crystals were grown from N, N dimethyl formamide (DMF) by restricted evaporation method at room temperature. The solubility of 8-HQP was determined in different solvents at various temperatures. The structural characterization of the grown crystals was carried out by X-ray diffraction. Vibrational modes were classified on the basis of group theoretical analysis and the spectral bands were compared with those of parent compounds in order to propose a tentative assignment by recording FT-IR, FT-Raman and polarized Raman spectra in different crystal orientations. The crystal possess lower cut-off at 230 nm and good transparency as confirmed by optical transmittance studies.

Optical properties of γ-Fe2O3 nanoparticles dispersed on sol–gel silica spheres

Two types of γ-Fe2O3 nanoparticles, pure γ-Fe2O3 and γ-Fe2O3 dispersed on sol–gel silica spheres (γ-Fe2O3/SiO2) in thin film form were prepared by the sol–gel technique. Transmission electron microscopy, X-ray diffraction, optical transmittance and FTIR studies along with photoluminescence measurements were carried out for characterizing the samples. The X-ray diffraction patterns of both γ-Fe2O3 nanoparticles and γ-Fe2O3/SiO2 indicated their phase-pure forms which were supported by the FTIR spectra. The average sizes of the nanoparticles obtained from transmission electron microscopy studies were ∼4nm for both types of samples. Optical transmittance studies indicated direct allowed transitions with two band gaps at ∼2.43 and 3.07eV. Although both types of samples showed excitonic luminescence at ∼2.38eV (at room temperature), the luminescence intensity of the γ-Fe2O3/SiO2 was higher than that of pure γ-Fe2O3.

Synthesis of CuInS2 by chemical route: optical characterization

Abstract CuInS2 powder was prepared by wet chemical route. The chalcopyrite structure of the powder was revealed by XRD studies. Raman measurements of the powder sample indicated four prominent peaks at 292, 305, 340 and 472 cm−1. The possible origin of the 305 cm−1 peak was investigated and was found to be some local vibration in the structure. The peaks at 292 and 340 cm−1 were ascribed to A1 and B2 modes, respectively. The peak at 472 cm−1 which was due to the formation of SO4−2 ion at lower pH value of the precursor solution could be eliminated by using pH>11.0. Photoluminescence (PL) studies of the CuInS2 powder indicated two distinct peaks at 1.49 and 1.42 eV. Post deposition annealing treatment in H2 atmosphere revealed the formation of excess sulphur vacancy leading to the peak at 1.42 eV in the PL spectra while O2 annealing of the powder created a deep defect level at 1.10 eV. Thick CuInS2 films were prepared by Doctor's blade technique. Optical transmittance studies of these films indicated direct allowed transition at ∼1.5 eV.

Effect of niobium substitution in stoichiometric lithium tantalate (SLT) single crystals

Optical-quality near-stoichiometric lithium tantalate (SLT) crystals doped with Nb were grown by top seeded solution growth technique using induction-heating system. The crystalline wafers were subjected to optical transmittance studies and coercive field measurements. The optical transmittance spectra of doped crystals show a shift in the absorption edge towards longer wavelength side. A change in Curie temperatures with respect to doping concentrations of Nb has been observed. Hysteresis measurements reveal that the coercive field value increases for increasing niobium concentration. It has also been observed that there is a significant increase in the internal field value for Nb-doped SLT crystals.

CuIn(S xSe 1− x) 2 films prepared by graphite box annealing of In/Cu stacked elemental layers

CuIn(S x Se 1− x ) 2 films were synthesized by sulphurization of In/Cu stacked elemental layers deposited onto glass and Mo-coated glass substrates followed by selenization by graphite box annealing. The films, thus synthesized, were characterized by measuring electrical, optical and microstructural properties. The microstructure and hence the physical properties of the films depended critically on the amount of sulphur incorporation. Nature of charge carriers depended on Cu/In, (S+Se)/(Cu+In) and S/(S+Se) ratios while their concentrations varied between 10 16 and 10 19 cm −3. Grain boundary scattering effects were critically studied by measuring the electrical conductivity ( σ) and Hall mobility ( μ) simultaneously on the same sample. Optical transmittance studies indicated the band gap to vary within 0.98–1.40 eV with x values. The photoluminescence spectra, recorded at 80 K were dominated by the excitonic peak located within 1.40–1.16 eV followed by a small peak within ∼0.96–0.98 eV arising due to transition from conduction band to neutral acceptor ( V Cu) or exciton bound to ionized acceptor (Cu In) states.

98/03938 Optical transmittance and photoconductivity studies on ZnO:Al thin films prepared by the sol-gel technique

98/03938 Optical transmittance and photoconductivity studies on ZnO:Al thin films prepared by the sol-gel technique

Optical transmittance and photoconductivity studies on ZnO : Al thin films prepared by the sol–gel technique

Polycrystalline ZnO : Al thin films have been prepared by the (Sol–gel) chemical deposition method. The ZnO : Al thin films are very transparent (∼90%) in the near UV, VIS and IR regions. The films are oriented along the c-axis ([0 0 2] direction) in the hexagonal structure. It is known that pure ZnO thin films are not chemically stable in corrosive media, but aluminium stabilizes the ZnO system and increases its electrical conductivity. Finally, the ZnO : Al thin films are reasonably stable under storage in air and in reactive atmospheres like O 2, H 2O, H 2 or in weak acids. Dark- and photo-conductivity of the ZnO : Al films are very high (1–100 Ω −1 cm −1), so that they can be used as transparent conductors in solar cells or in electrochromic devices.

X-ray photoelectron spectroscopy, scanning electron microscopy and optical transmittance studies of indium tin oxide and cadmium sulphide thin films for solar cells

Thin indium tin oxide (ITO) films were deposited onto borosilicate glass by d.c. sputtering from an oxide target (91 mass% In 2O 3 and 9 mass% SnO 2). CdS thin films suitable for solar cells were obtained by chemical bath deposition (CBD) from aqueous solutions of CdSO 4 and thiourea followed by thermal annealing of the layers deposited onto the electroconductive glass. The chemical changes occurring on the surface of ITO and CdS layers, as evidenced by X-ray photoelectron spectroscopy during their preparation, are discussed. The surface topography and optical properties of ITO/glass and CdS/ITO/glass films were characterized by scanning electron microscopy and optical transmittance.

An electrochromic window based on a modified polypyrrole/nickel oxide combination

A novel type of electrochromic system based on the combination of an organic polypyrrole electrode with an inorganic nickel oxide electrode in an aqueous electrolyte has been fabricated. The characteristics and performance of this device have been investigated and determined by ‘in situ’ electrochemical (cyclic voltammetry) and optical (transmittance) studies. The results suggest that the device may be of interest as a light-modulation window, especially for all those applications where cost and reliability are the key requisites.

Optical transmittance and microgravimetric studies of the oxidation of 〈100〉 single crystal films of copper

Thin single crystal copper films have been grown and oxidized on (100) faces of cleaved sodium chloride discs suspended from a vacuum ultramicrobalance. Optical transmittance measurements between 400–800 nm and electron microscopic investigations were also used to characterize the oxidation process. Polycrystalline copper films grown at room temperature are substantially the same as those grown previously on glass substrates. Single crystalline growth at 325 ° C on rock salt produces a characteristic transmittance curve due to the “island” nature of the films. These curves compare favorably with other previously published results. Single crystal copper films oxidized to CuO0.67 at temperatures of 117–159°C in 100 Torr of oxygen for films less than 500 A thick. For films 378 to 1000 Å thick, compositions of CuO0.52 to CuO0.62 were obtained between 123–176°C. The oxidation to less than CuO0.67 is attributed to the existence of islands in these films which are thicker than the average film thickness, and require higher temperatures or thinner films to permit oxidation to CuO0.67 before the nucleation of CuO sets in.