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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]

ZnO nanowires were hydrothermally grown on sputtered gallium and aluminium co-doped ZnO (GAZO) thin films as seed layers and the effect of seed layer annealing temperature on their microstructural and optoelectronic properties was investigated. Atomic force microscopy revealed an increase in the GAZO films' mean particle size and surface roughness with annealing temperature. The GAZO films exhibited a zincite phase with a preferred orientation along the (002) plane and their crystallinity improved with annealing temperature, resulting in low electrical resistivity. The nanowires' alignment improved with seed layer annealing temperature up to 150 °C and then deteriorated at 250 − 350 ° C . This was attributed to the improvement in nanowire crystallinity up to 150 °C and its deterioration at 250–350 °C. Energy dispersive spectroscopy confirmed that the nanowires were closer to stoichiometric ZnO (1:1). Raman spectroscopy revealed the presence of few defects and slight residual tensile stress in the nanowires, in corroboration with XRD analysis. The films and nanowires exhibited average visible transmittances around 75–85% and 50–80%, respectively. The least electrical resistivity ( 7.0 × 10 − 3 Ω cm ) and highest figure of merit ( 1.02 × 10 − 2 Ω − 1 ) were obtained for the well-aligned nanowires grown on 150 °C annealed films, demonstrating their suitability for solar cell transparent electrode fabrication. [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 and aluminium co-doped zinc oxide (GAZO) thin films were deposited by radio frequency (rf) magnetron sputtering onto glass substrates and the effect of rf power on their structural, optical and electrical properties was respectively investigated by X-ray Diffraction (XRD), Spectrophotometry and Four–Point Probe Resistivity measurements. All films had a hexagonal wurtzite crystal structure with a preferred (002) grain orientation. The films’ crystallinity deteriorated with increasing rf power from 150 W to 250 W as revealed by the increase in full width at half maximum (FWHM), decrease in mean crystallite size and increase in dislocation density. A further increase in rf power to 300 W caused slight improvements in crystallinity due to enhanced surface diffusion of the ad-atoms. High optical transmittances, around 80–90% were observed for all films in the visible region and their optical band gap red shifted from 3.32 eV to 3.20 eV with increasing rf power. The electrical resistivity firstly increased as the rf power changed from 150 W to 250 W and then decreased at 300 W. The lowest electrical resistivity of 5.0 × 10 − 1 Ω c m and maximum figure of merit of 4.8 × 10 − 4 Ω − 1 were obtained for films deposited at 150 W, indicating their better performance in optoelectronic applications. [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]

Non-isothermal Differential Scanning Calorimetric (DSC) studies were done on Se 100− X M(M=In, Sb) X chalcogenide glasses prepared by the melt quenching technique. The composition-dependent activation energy for glass to crystal transformation (Δ E c ) and the pre-exponential factor ( K o ) of the Arrhenius expression were obtained on the basis of the Augis and Bennett׳s method. A linear dependence between Δ E c and ln K 0 was observed in both systems implying the existence of compensation effects of the Meyer-Neldel type. These compensation effects confirmed the applicability of Meyer-Neldel Rule (MNR) for the non-isothermal crystallization in the present systems. [ABSTRACT FROM AUTHOR]

Abstract: Zinc oxide possesses many interesting properties, such as modifiable conductivity, wide band gap, high excitonic binding energy, piezo-electric polarisation and cathodoluminiscence. In this study transparent conducting aluminium doped zinc oxide (ZnO:Al) thin films were deposited on float glass substrates by tailor made spray pyrolysis with adaptation for measuring the actual temperature of the substrate surface during deposition. The films were characterised and the effect of aluminium doping concentration [Al/Zn] on their optical, electrical and structural properties was investigated as a function of aluminium doping between 0 and 10at.%. There was widening of optical band gap with increasing doping concentration. ZnO:Al films with low resistivity of 2.8×10−2 Ωcm and high transmittance of over 85% at 550nm which are crucial for opto-electrical applications were obtained at a doping ratio of 2at.%. [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]

Aluminum and gallium co-doped ZnO (AGZO) thin films were grown by simple, flexible and cost-effective spray pyrolysis method on glass substrates at a temperature of 230 °C. Effects of equal co-doping with aluminum (Al) and gallium (Ga) on structural, optical and electrical properties were investigated by X-ray diffraction (XRD), UV–vis–NIR spectrophotometry and Current–Voltage (I–V) measurements, respectively. XRD patterns showed a successful growth with high quality polycrystalline films on glass substrates. The predominant orientation of the films is (002) at dopant concentrations ≤2 at% and (101) at higher dopant concentrations. Incorporation of Al and Ga to the ZnO crystal structure decreased the crystallite size and increased residual stress of the thin films. All films were highly transparent in the visible region with average transmittance of 80%. Increasing doping concentrations increased the optical band gap, from 3.12 to 3.30 eV. A blue shift of the optical band gap was observed from 400 nm to 380 nm with increase in equal co-doping. Co-doping improved the electrical conductivity of ZnO thin films. It has been found from the electrical measurements that films with dopant concentration of 2 at% have lowest resistivity of 1.621×10 −4 Ω cm. [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: We report on the crystallization processes and structure (crystal phases) of Ag33Ge17Se50 glassy alloy using differential scanning calorimetry and x-ray diffraction techniques, respectively. The devitrification that gives rise to the first exothermic peak results in the crystallization of Ag2Se and Ag8GeSe6 phases, while the growth of GeSe2 accompanied by the transformation of Ag8GeSe6 to Ag2Se phase occurs during the second crystallization process. Different theoretical models are used to elucidate various kinetic parameters for the crystallization transformation process in this phase separated system. With annealing below the glass transition temperature, an inverse behavior between the variation of the optical gap and the band tailing parameter is observed for the thermally evaporated films. These results are explained as the mixing of different clusters/species in the amorphous state and/or changes caused by structural relaxation of the glassy network for the thermally evaporated films. [Copyright &y& Elsevier]

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]