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Highlights • Optical properties of GAZO films sputtered at various O 2 /Ar flow ratios were studied. • The films had nearly spherical grains of mean diameter around 50–100 nm. • Good microstructural and optical properties were at 0.667 O 2 /Ar flow ratio. • The prepared GAZO thin films can be used for optoelectronic device fabrication. Abstract The present study investigates the effect of oxygen admittance on the surface morphology and optical constants of gallium (Ga) and aluminium (Al) co-doped zinc oxide (GAZO) thin films deposited on glass substrates by radio frequency (RF) planar magnetron sputtering. The GAZO thin films were uniformly covered with almost spherical grains of mean diameter around 50–100 nm. In the visible region, the refractive index (n) exhibited a decreasing trend with increasing oxygen admittance and the extinction coefficient (k) was almost zero, corroborating the observed increase in transmittance with oxygen/argon (O 2 /Ar) flow ratio. Optical constants such as the Wemple and Didomenico (WDD) single oscillator dispersion energies (E o and E d), static refractive index (n 0) , dielectric constant (ε), plasma frequency (ω p) and free carrier concentration (N c) were determined. Desirable surface morphology and optical properties were observed on the GAZO thin films deposited at an O 2 /Ar flow ratio of 0.667 , indicating their suitability for optoelectronic device fabrication. [ABSTRACT FROM AUTHOR]

Ga and Al co-doped ZnO thin films were prepared on glass substrates by radio frequency magnetron sputtering and the effect of O 2 /Ar flow ratio on their physical properties was investigated. The films exhibited a hexagonal wurtzite structure with a predominant (002) peak intensity and their crystallinity improved with O 2 /Ar flow ratio. Raman spectroscopy confirmed the films’ wurtzite structure and revealed a decrease in residual tensile stress and charge carrier concentration with increasing O 2 /Ar flow ratio. Low surface roughness resulted in high optical transmittances around 85–90% in the visible region. The Urbach energy decreased with increasing O 2 /Ar flow ratio indicating a reduction in structural disorders. This was consistent with Raman spectroscopy and X-ray diffraction analysis. The least electrical resistivity ( 2.6 × 10 1      Ω cm ) and highest figure of merit (8.8 × 10 −6 Ω −1 ) for films prepared with oxygen admittance were obtained at 0.667 O 2 /Ar flow ratio, indicating their suitability in optoelectronic device fabrication. [ABSTRACT FROM AUTHOR]

Amorphous thin films of Se 86-x Te 10 Sb 4 Bi x (x = 0, 2, 4, 6 and 8) were synthesized by electron-beam deposition of the premelt quenched bulk samples. Swanepoel’s standard envelope method was used to determine optical properties from spectrophotometric measurements in the UV–VIS-NIR spectral region. Tauc’s extrapolation method and Wemple-Didomenico single oscillator model where used to determine the optical band gap energy ( E g opt ) in the region where the absorption coefficient α ≥ 10 4 cm −1 . The values of E g opt decreased with increasing Bi additive. The complex dielectric constant ( ε ), Urbach energy ( E u ), optical conductivity ( σ ), plasma frequency ( ω P ), single oscillator parameters ( E o and E d ) and lattice dielectric constant ( ε L ) were determined. The changes noticed in optical parameters with Bi content were explained on the basis of chemical bond approach, increased defect states and increased density of localized states in the mobility gap. [ABSTRACT FROM AUTHOR]

Thin films of Se 79 Te 10 Sb 4 Bi 7 , were prepared by Electron beam deposition technique. The structure of the as-prepared and annealed films has been studied by X-ray diffraction and the surface morphology by the scanning electron microscope (SEM). These studies show that there is a gradual change in structure and the formation of some polycrystalline structures in the amorphous phases is observed when the Se 79 Te 10 Sb 4 Bi 7 film is annealed in the temperature range of 333–393 K. The optical transmission of these films has been studied as a function of photon wavelength in the range 300–2500 nm. It has been found that the optical band gap E g o p t decreased with increasing annealing temperature in the range 333–393 K. The Urbach energy ( E u ), optical conductivity ( σ opt ), imaginary ( ε i ), and real ( ε r ) parts of the complex dielectric constant ( ε ) and lattice dielectric constant ( ε L ) were also determined. The changes noticed in optical parameters with increasing annealing temperature were explained on the basis of structural relaxation as well as change in defect states and density of localized states due to amorphous-crystalline transformation. [ABSTRACT FROM AUTHOR]

Gallium-doped zinc oxide (GZO) thin films were deposited onto glass substrates by the spray pyrolysis technique and the effect of gallium (Ga) doping on their structural, optical and electrical properties was investigated by X-ray Diffraction (XRD), Spectrophotometry and Current–Voltage ( I – V ) measurements, respectively. XRD studies revealed that all films were polycrystalline in nature, with a hexagonal wurtzite crystal structure and a predominant (002) c -axis orientation. Ga doping resulted in deterioration of the film's crystallinity, increase in full width at half maximum (FWHM) and reduction in the mean crystallite sizes. All GZO thin films had relatively higher average transmittances, approximately 70–85% in the visible region as compared to the undoped ZnO thin films. Introduction of Ga led to a blue shift in the optical band gap from 3.26 eV to 3.30 eV and an increase in the Urbach energy from around 67 meV to 100 meV. Ga doping induced a decrease in sheet resistance leading to a minimum electrical resistivity of 1.2 Ω cm and a maximum figure of merit of 1.02 × 10 − 4 Ω − 1 for the 1 at% GZO thin film, indicating its suitability for optoelectronic applications, especially transparent electrode fabrication. [ABSTRACT FROM AUTHOR]

The measurements and analysis of optical transmission and far-infrared (IR) reflectivity spectra of thermally evaporated Sb2Se3:Sn films are reported. The refractive index and film thickness have been determined from the upper and lower envelopes of the transmission spectra (Swanepoel's standard envelope method), measured at normal incidence, in the spectral range from 800 to 2500 nm. Values of the refractive index fit well to Cauchy's dispersion relation. The optical gap decreases with an increase in the Sn content, while a maximum in the tailing parameter and Urbach's energy occurs with only a small amount (∼1 at %) of this additive. Characteristic vibrational bands for SbSe3 structural units are revealed in the far-IR spectrum with no additional ones arising from the Sn additive. The Kramers-Kronig analysis has been used to calculate the dielectric constants and hence the longitudinal optic and transverse optic splitting for various compositions. The inclusion of Sn as a charged entity along with the Coulomb interactions which serve to polarize the glass medium is found to be responsible for these results. [ABSTRACT FROM AUTHOR]

Abstract: Indium tin oxide (ITO) thin films were prepared by RF sputtering of ceramic ITO target in pure argon atmosphere at a high base pressure of 3×10−4 mbar without substrate heating and oxygen admittance. The use of pure argon during deposition resulted in films with high transparency (80–85%) in the visible and IR wavelength region. The films were subsequently annealed in air in the temperature range 100–400°C. The annealed films show decreased transmittance in the IR region and decreased resistivity. The films were characterized by electron microscopy, spectrophotometry and XRD. The predominant orientation of the films is (222) instead of (400). The transmission and reflection spectra in the wavelength range 300–2500nm are used to study the optical behaviour of the films. The optical transmittance and reflectance spectra of the films were simultaneously simulated with different dielectric function models. The best fit of the spectrophotometric data was obtained using the frequency-dependent damping constant in the Drude model coupled with the Bruggeman effective medium theory for the surface roughness. It has been found that the sputtering power and the chamber residual pressure play a key role in the resulting optical properties. This paper presents the refractive index profile, the structure determined from the XRD and the electrical properties of ITO films. It has been found from the electrical measurement that films sputtered at 200W power and subsequently annealed at 400°C have a sheet resistance of 80Ω/□ and resistivity of 1.9×10−3 Ωcm. [Copyright &y& Elsevier]

The development of transparent conducting oxide materials has gained an increased interest in the scientific community for developing efficient low cost optoelectronic devices. The effect of Cd precursor on structural and optical properties of sol-gel synthesized Zn0:9Cd0:1O nanostructured films has been studied by using XRD, AFM, optical absorption and emission spectroscopic techniques. X-ray diffraction confirms the hexagonal wurtzite crystal structure of the deposited films and the relative intensity of diffraction peaks has been observed with different cadmium salts. The granular surface morphology of the synthesized films has been observed from AFM measurements. The optical transmission, band gap and luminescence intensity was found to change for different cadmium salts. These results are very important for developing new materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Ternary thin film alloys of Se 90-X In 10 Sb X (x = 1, 4, 10, 15 and 20) were synthesised by flash evaporation of the pre-melt quenched bulk samples under a vacuum of 10 −5 Torr. Optical absorption analysis pointed to indirect allowed transitions as the mechanism of excitation across the energy gap. The optical band gap (E g ) was evaluated on the basis of Wemple-Didomenico single oscillator model and Tauc's extrapolation method in the spectral region where the absorption coefficient, α ≥ 10 4 cm −1 . The refractive index (n), complex dielectric constant ( ε ), band tailing parameter (B), plasma frequency (ω p ), single oscillator parameters (E o and E d ) and lattice dielectric constant (ε L ) were deduced for each alloy. The compositional dependence of optical and dielectric parameters was explained on the basis of chemical bond approach. The observed shift in the trends of E g , E d , ε L and ω p values at the composition where Sb = 4 at% was correlated to the usual chemical threshold at this composition. [ABSTRACT FROM AUTHOR]

This paper reports the effect of Ag photo-doping on optical, electrical and structural properties of GeTe:Ag thin films. The absence of sharp diffraction peak confirms the amorphous nature of as-deposited and photo-doped films. The decrease in reflectance of GeTe:Ag bilayer films with photo-doping reaction time has been observed. The RAMAN spectrum showed the characteristic Raman bands for GeTe 4 (127 cm −1 ), long chain interactions of Te–Te chains (145 cm −1 ) and a broad peak for Ge–Ge vibrations (275 cm −1 ) without appreciable change in their position/shape with photodoped Ag concentration. The electrical resistivity measurement shows that photo-doping of Ag led to sharp amorphous-crystalline phase transition along with an increase in transition temperature and resistivity value in both amorphous as well as crystalline state. The annealing of photo-doped GeTe:Ag samples showed an enhancement in the crystallinity of GeTe phase without any segregation of Ag phases in annealed samples. The preferential formation of GeTe (200) phase upon crystallization has been observed for GeTe:Ag films. Different optical parameters have been calculated for photo-doped and annealed samples and are discussed in conjunction with the modification of network structure of GeTe with inclusion of photo-doped Ag content. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the spectroscopic studies on the thermally evaporated Sn x Sb20Se80 − x (2≤ x ≤8) films. Optical gap and band tailing parameter decreases except for x =8, where it increases. The red shift in peak reflectivity spectrum in the interband transition region (200–800nm) has been observed. The position and shape of the reflectivity bands (80–378cm−1) indicate the change in the local structure of the films. The Kramer–Kronig transformations have been used to evaluate the dielectric constants from the far-infrared reflectivity spectrum. Splitting of the longitudinal optic and transverse optic mode characterizes the partial ionic character for Sn–Sb–Se system. The relationship between the optical properties and structure has been revealed. [ABSTRACT FROM AUTHOR]

• Zn 1.5+x Sn 1.5-x O 4 nanostructured films by acetylacetone as sol gel precursor solvent. • Cubic phase with (311) alignment minimal defects for x = 0.75 films. • Raman active modes corresponding to F 2g and A 1g modes for Zn 2 SnO 4 system. • Enhancement in defect related visible emission from the stoichiometric Zn 2 SnO 4 films. • Lowest electrical resistivity 8.4 × 10−3 Ω-cm and maximum FOM of 0.09 Ω−1 for x = 0.75. This work reports the structure-property relationship of sol gel synthesized Zn 1.5+x Sn 1.5-x O 4 films using acetylacetone as precursor solvent and stabilizer. These samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, optical spectroscopy and Hall measurements. XRD study reveals the preferentially grown along (311) with a change in its intensity for different compositions in Zn-Sn-O system. The surface morphology varies with composition has been observed in both SEM and AFM studies. The dominant Raman active modes were observed at 556 and 667 cm−1 corresponding to F 2g and A 1g modes respectively of Zn 2 SnO 4 system. The optical gap varies between 3.85 eV to 3.96 eV and defect related emission spectra dominate the luminescence characteristics for the present system. The minimum electrical resistivity 8.4 × 10−3 Ω-cm and maximum figure of merit of 0.09 Ω−1 has been found for Zn 2.25 Sn 0.75 O 4 films. These results show their suitability for fabrication of transparent conductors and other sensing device applications. [ABSTRACT FROM AUTHOR]

Abstract: Bulk sample of (Se80Te20)96Ag4 was prepared by quenching technique. Thin films of (Se80Te20)96Ag4 glasses of different thickness (500–950nm) were deposited on dry clean glass substrates by thermal evaporation technique. Energy dispersive X-ray spectroscopy (EDX) indicates that samples are nearly stoichiometric. X-ray diffraction patterns indicate that they are in the amorphous state. The optical constants, refractive index, absorption index, and optical band gap have been calculated from transmittance and reflectance data in spectral range of 400–2500nm. It has been found that the optical band gap decreases, but the refractive index, extinction coefficient, optical conductivity, real and imaginary dielectric constant increase with increase in thickness of (Se80Te20)96Ag4 thin films. The results are discussed on the basis of rearrangements of defects and disorders in the chalcogenide systems. [Copyright &y& Elsevier]