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Effects of Al doping on defect behaviors of ZnO thin film as a photocatalyst

Yu Fucheng, Hu Hailong, Wang Bolong, Li Haishan, Song Tianyun, Xu Boyu, He Ling, Wang Shu, Duan Hongyan

Materials Science Poland

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2019

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Vol. 37, No. 3

437--445

EN

Al doped ZnO (AZO) thin films were prepared on silica substrates by sol-gel method. The films showed a hexagonal wurtzite structure with a preferred orientation along c-axis. Suitable Al doping dramatically improved the crystal quality compared to the undoped ZnO films. Dependent on the Al dopant concentration, the diffraction peak of (0 0 2) plane in XRD spectra showed at first right-shifting and then left-shifting, which was attributed to the change in defect concentration induced by the Al dopant. Photocatalytic properties of the AZO film were characterized by degradation of methyl orange (MO) under simulated solar light. The transmittance of the films was enhanced by the Al doping, and the maximum transmittance of 80 % in the visible region was observed in the sample with Al concentration of 1.5 at.% (mole fraction). The film with 1.5 at.% Al doping achieved also maximum photocatalytic activity of 68.6 % under solar light. The changes in the film parameters can be attributed to the variation in defect concentration induced by different Al doping content.

2

Preparation and spectroscopic analysis of zinc oxide nanorod thin films of different thicknesses

Mia N. H., Rana S. M., Pervez F., Rahman M. R., Hossain K., Al Mortuza A., Basher M. K., Hoq M.

Materials Science Poland

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2017

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Vol. 35, No. 3

501--510

EN

Zinc oxide thin films with different thicknesses were prepared on microscopic glass slides by sol-gel spin coating method, then hydrothermal process was applied to produce zinc oxide nanorod arrays. The nanorod thin films were characterized by various spectroscopic methods of analysis. From the images of field emission scanning electron microscope (FESEM), it was observed that for the film thickness up to 200 nm the formed nanorods with wurtzite hexagonal structure were uniformly distributed over the entire surface substrate. From X-ray diffraction analysis it was revealed that the thin films had good polycrystalline nature with highly preferred c-axis orientation along (0 0 2) plane. The optical characterization done by UV-Vis spectrometer showed that all the films had high transparency of 83 % to 96 % in the visible region and sharp cut off at ultraviolet region of electromagnetic spectrum. The band gap of the films decreased as their thickness increased. Energy dispersive X-ray spectroscopy (EDS) showed the presence of zinc and oxygen elements in the films and Fourier transform infrared spectroscopy (FT-IR) revealed the chemical composition of ZnO in the film.

3

(0 0 2)-oriented growth and morphologies of ZnO thin films prepared by sol-gel method

Guo D., Ju Y., Fu C., Huang Z., Zhang L.

Materials Science Poland

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2016

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Vol. 34, No. 3

555--563

EN

Zinc acetate was used as a starting material to prepare Zn-solutions from solvents and ligands with different boiling temperature. The ZnO thin films were prepared on Si(1 0 0) substrates by spin-coating method. The effect of baking temperature and boiling temperature of the solvents and ligands on their morphologies and orientation was investigated. The solvents and ligands with high boiling temperature were favorable for relaxation of mechanical stress to form the smooth ZnO thin films. As the solvents and ligands with low boiling temperature were used to prepare Zn-solutions, the prepared ZnO thin films showed (0 0 2) preferred orientation. As n-propanol, 2-methoxyethanol, 2-(methylamino)ethanol and monoethanolamine were used to prepare Zn-solutions, highly (0 0 2)-oriented ZnO thin films were formed by adjusting the baking temperature.

4

Growth orientation transition and metal-like conductivity of Ti, Al co-doped ZnO films

Jiang M., Liu X., Wang H., Xu J.

Materials Science Poland

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2010

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Vol. 28, No. 1

273--280

EN

Ti, Al co-doped ZnO thin films have been fabricated by radio frequency magnetron sputtering and post-vacuum-annealing techniques on glass substrates. For annealing temperatures below 723 K, the room temperature resistivity of these films was found to decrease as the annealing temperature increased. The lowest resistivity (6.75×10-4 ?ocm), indicating metal-like conductivity, was found at 723 K. The post-annealing temperature dependent on the resistivity of these films also showed a metal - semiconductor transition at 723 K. It was also found a growth orientation transition of these films from (002) to (100) with the annealing temperature up to 773 K.

5

The influence of the prefiring temperature on the structure and surface morphology of sol-gel derived ZnO film

Hwang K. S., Hwangbo S., Kim J. T.

Materials Science Poland

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2009

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Vol. 27, No. 1

159--170

EN

Show aC-axis oriented ZnO thin films were prepared on silica glass substrates by the sol-gel method using a zinc naphthenate precursor. As-deposited films were prefired at 250 °C for 60 min, at 350 °C for 30 min, and at 500 °C for 10 min, followed by final annealing at 600-900 °C in air. Crystal structure, surface morphology, surface roughness and transmittance at the visible range were analyzed by high resolution X-ray diffraction, field emission scanning electron microscopy, scanning probe microscopy, and ultraviolet spectrophotometry. (002)-oriented ZnO films were obtained by annealing at 600 °C, and at higher temperatures for the films prefired at 350 °C and 500 °C. All the films exhibited a high transmittance, above 80%, in the visible region, and showed a sharp fundamental absorption edge at 0.38-0.40 žm. The most highly c-axis oriented ZnO with a homogeneous surface was observed at a prefiring temperature of 350 °C.