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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]

Gallium and aluminium co-doped zinc oxide (GAZO) thin films were prepared on glass substrates at low temperatures by radio frequency (rf) magnetron sputtering and their physical properties were investigated. All films possessed a hexagonal wurtzite crystal structure with a strong growth orientation along the (0 0 2) c-axis. The (0 0 2) peak intensity and mean crystallite size increased with substrate temperature from room temperature (RT) to 75 °C and then decreased at 100 °C, indicating an improvement in crystallinity up to 75 °C and its deterioration at 100 °C. Scanning electron microscopy (SEM) micrographs revealed the strong dependency of surface morphology on substrate temperature and energy dispersive spectroscopy (EDS) confirmed the incorporation of Ga and Al into the ZnO films. All films exhibited excellent transmittances between 85 and 90% in the visible region and their optical band gap increased from 3.22 eV to 3.28 eV with substrate temperature. The Urbach energy decreased from 194 meV to 168 meV with increasing substrate temperature, indicating a decrease in structural disorders which was consistent with X-ray Diffraction (XRD) analysis. Films deposited at 75 °C exhibited the lowest electrical resistivity (2.4 Ωcm) and highest figure of merit (7.5 × 10 −5 Ω −1 ), proving their potential as candidates for transparent electrode fabrication. [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]

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]