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

Abstract

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.

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Photoelectric Properties of Screen-Printed Al-Doped ZnO Films

Photoelectric Properties of Screen-Printed Al-Doped ZnO Films

The potential of cheap semiconductor materials in the area of solar energy use is illustrated by the example of zinc oxide (pure and Al-doped in various concentrations). Under investigation was the electric conductivity and photoelectric properties of ZnO thin films. The samples were prepared using screen-printing technique. The results of measurements point to non-linear relationships between Al concentration, photosensitivity and electrical conductivity of thin ZnO films. Optimal Al concentration for practical use of ZnO in photovoltaic devices is found to be ~ 1%. The experimental methods, technologies and results described in the paper could be used for further investigations in this area.

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Al-doped ZnO films deposited by magnetron sputtering: effect of sputtering parameters on the electrical and optical properties

Abstract

Aluminum-doped zinc oxide (AZO) thin films were prepared by magnetron sputtering method. The influences of deposition pressure, substrate temperature, Ar flow rate and film thickness on optical and electrical properties were investigated using ultraviolet-visible (UV-Vis) spectrometer and Hall measurements. The experimental results revealed that a low resistivity, smaller than 4 × 10-4 Ω·cm, was obtained when the deposition pressure was smaller than 0.67 Pa and substrate temperature about 200 °C. Ar flow rate had a small influence on the resistivity but a big influence on the transparency at near infrared range (NIR). We obtained optimized AZO thin films with high ponductivity and transparency at low deposition pressure, small Ar flow and appropriate temperature (around 200 °C). The etching behavior of the AZO thin films deposited at the different Ar flow rates was also studied in this paper. The results show that Ar flow rate is a very important factor affecting the etching behavior.

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Effects of aluminum (Al) incorporation on structural, optical and thermal properties of ZnO nanoparticles

Abstract

In this research article, pure and 1 %, 3 % and 5 % aluminium doped zinc oxide nanoparticles (NPs) were prepared via sol-gel method and then calcined at 500 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, UV-Vis spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques were used to investigate the structural, optical and thermal properties of synthesized pure and Al doped ZnO nanoparticles. Energy dispersive X-ray spectroscopy (EDX) analysis revealed high purity of nanoparticles in the synthesized products without any impurity peaks. Mean dimension of the nanoparticles was ~28 nm and they were hexagonal in shape, according to the images analyzed by transmission electron microscope (TEM). The optical absorption spectra of pure and Al doped ZnO samples studied using UV-Vis spectrometry have been presented and we have observed that the band gap increases with increasing Al concentration. In FT-IR spectra, the broad absorption peaks around 485 cm−1 and 670 cm−1 were assigned to Zn–O vibration. Above 450 °C, the TG curve became flat what means there was no weight loss. In the DSC curve it is seen that the transition at 150 °C was highly exothermic because of structural relaxation and on doping the exothermic peaks became shifted to the lower value of temperature. These types of materials are very useful in optoelectronics applications.

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Optical Modeling and Simulation of Tandem Metal Oxide Solar Cells

Abstract

An investigation of silicon-based tandem solar cells incorporating Al-doped ZnO (AZO) and Cu2O metal oxides, via two of the most efficient methods of optical modeling, specifically ray tracing and transfer matrix algorithms, was performed. The simulations were conducted based on specialized software, namely Silvaco Atlas and MATLAB, as well as on OPAL2 simulation platform. The optical analysis involved the calculation of the spectral curves for reflectance, absorptance and transmittance for different thicknesses of the thin film layers constituting the cell. It was established the optimum thickness of the AZO layer based on the minimum reflectance and maximum transmittance. Moreover, several materials were investigated in order to determine the optimum buffer layer for the tandem solar cell, based on optical modeling. The optical parameters of the ZnO/Cu2O top subcell were optimized, in order to achieve the highest conversion efficiency of such heterojunction solar cell.

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Facile microwave-assisted synthesis of Al:Mn co-doped PbI2 nanosheets: structural, vibrational, morphological, dielectric and radiation activity studies

Abstract

Herein, we report a successful development of nano-scale pure and Al and Mn co-doped PbI2 using facile microwaveassisted route. Structural study was done through X-ray diffraction analysis of grain size, dislocation density and lattice strain. The crystallite size was found to vary from 28 nm to 40 nm due to Al:Mn co-doping in PbI2. The presence of various vibrational modes was confirmed by FT-IR spectroscopy and red shifting was observed in peak positions compared to the bulk. Surface morphology, examined using a scanning electron microscope, confirmed the formation of single crystal nanosheets of a thickness in the range of 10 nm to 30 nm. The single crystal nanosheets were found to be transformed to large area nanosheets due to the doping. Enhancement in dielectric constant from ~7.5 to 11 was observed with increasing Al doping concentration. Linear attenuation coefficient was calculated and showed the enhancement of blocking gamma rays with increasing doping concentration. Its value was found to increase from 7.5 to 12.8 with the doping. The results suggest that the synthesized nanostructures can be used for detection and absorption of gamma rays emitted by 137Cs and 241Am sources.

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Drug use in Ghana: knowledge, perceptions, and attitudes in a small group of elite student sportspersons

-seeking behaviours among elite athletes Journal of Science and Medicine in Sport 2011; 14: 278-282. 11. Uvacsek M, Nepusz T, Naughton DP, et al. Self-admitted behaviour and perceived use of performance-enhancing vs psychoactive drugs among competitive athletes Scand J Med Sci Sports 2011; 21: 224-234. 12. Wanjek B, Rosendahl J, Strauss B, et al. Doping, Drugs and Drug Abuse among Adolescents in the State of Thuringia (Germany): Prevalence, Knowledge and Attitudes Int J Sports Med 2007; 28: 346-353. 13. World Anti-Doping Agency. The

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Structural and optoelectronic properties of glucose capped Al and Cu doped ZnO nanostructures

from 5 to 40° in the 2θ range. The intensity of the peaks was found to be maximum in case of ZnO:Al and it decreased consecutively in ZnO, ZnO:Cu, achieving the lowest value in ZnO:(Al,Cu). Thus, a decrease in crystallinity was observed from ZnO:Al to ZnO:Cu and finally to codoping. It was also observed that there was a slight shift in 2θ values for the doped samples with respect to that of pristine ZnO. In Al doped ZnO, the most preferred growth direction was [0 0 2] along with (1 0 1) shift towards the right whereas the shift towards the left was observed for Cu

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Structural and optical characterization of Cu doped ZnO thin films deposited by RF magnetron sputtering

. 3861–3877, 2011. [4] I. G. Dimitrov, A. O. Dikovska and P. A. Atanasov, “Al doped ZnO thin films for gas sensor application”, Journal of Physics: Conference series , vol. 113, 2008. [5] Ch. Jagadish, V. A. Coleman and S. J. Pearton, “Zinc oxide bulk, thin films and nanostructures”, Amsterdam, London: Elsevier, 1st edition , pp. 1–586, 2006. [6]Ü.Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Dogan, V. Avrutin, S. J. Cho and H. Morkoc, “A comprehensive review of ZnO materials and devices”, Journal Of Applied Physics , vol. 98, pp

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Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

SmBa 2 Cu 3 O 6+δ via Al doping and clustering. Europhys. Lett. , 76 (3), 443-449. Sudoh, K., Yoshida, Y., Takai, Y. (2004). Effect of deposition conditions and solid solution on the Sm 1+x Ba 2-x Cu 3 O 6+δ thin films prepared by pulsed laser deposition. Physica C , 384 (1-2), 178-184. Miyachi, K., Sudoh, K., Ichino, Y., Yoshida, Y., Takai, Y. (2003). The effect of the substitution of Gd for Ba site on Gd 1+x Ba 2-x Cu 3 O 6+δ thin films. Physica C , 392-396 (Part 1), 1261-1264.

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