Effect of the annealing temperature on transparency and conductivity of ZnO:Al thin films (original) (raw)
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Al-doped ZnO thin films by sol?gel method
Surface and Coatings Technology, 2004
Transparent and conductive high preferential c-axis oriented ZnO thin films doped with Al have been prepared by sol-gel method using zinc acetate and aluminium chloride as cations source, 2-methoxiethanol as solvent and monoethanolamine as sol stabilizer. Film deposition was performed by dip-coating technique at a withdrawal rate of 1.5 cm min on Corning 1737 glass y1 substrate. The effect of dopant concentration, heating treatment and annealing in reducing atmosphere on the microstructure as well as on the electrical and optical properties of the thin films is discussed. The optical transmittance spectra of the films showed a very good transmittance, between 85 and 95%, within the visible wavelength region. The minimum resistivity of 1.3=10 V y3 cm was obtained for the film doped with 2 wt.% Al, preheated at 400 8C and post-heated at 600 8C, after annealing under a reduced atmosphere of forming gas.
Preparation and characterization of Al doped ZnO thin films by sol–gel process
Journal of Alloys and Compounds, 2012
Transparent conductive ZnO films doped with 0-5 mol% of Al 3+ (or AZO films) were deposited on the soda-lime glass substrates by sol-gel multilayer dip-coating. The effects of the processing conditions, especially annealing in vacuum, on the structure, optical and electrical properties of the AZO films were investigated by XRD, Raman spectroscopy, TEM and SEM, spectrophotometer, four-point prober and Halleffect measurements. Al 3+-doping led to destruction and reorganization of ZnO structure, but AZO films still had a hexagonal wurtzite structure with a preferential orientation along (0 0 2) crystal plane. After annealed in vacuum, the AZO films had better optical transmittance (>90%) and conductivity (smaller by two orders of magnitude), since annealing in vacuum promoted the growth of grains and release of residual stress, and also decreased the defects and disorder in the films. But extending the vacuum annealing time, the grains grew along other orientations except (0 0 2) crystal plane, so that the film's square resistance became bigger. Carrier concentration ($2.3 Â 10 19 /cm 3) of annealed AZO films increased with increasing Al 3+ amount, but Hall mobility in the 1% Al-ZnO film was the biggest, $19.1 cm 2 /Vs.
Journal of Materials Science: Materials in Electronics, 2014
Al-doped zinc oxide (AZO) thin films are prepared on polycrystalline fluorine-doped tin oxide-coated conducting glass substrates from nitrates baths by the electrodeposition process at 70°C. The electrochemical, morphological, structural and optical properties of the AZO thin films were investigated in terms of different Al concentration in the starting solution. It was found that the carrier density of AZO thin films varied between -3.11 and -5.56 9 10 20 cm -3 when the Al concentration was between 0 and 5 at.%. Atomic force microscopy images reveal that the concentration of Al has a very significant influence on the surface morphology and roughness of thin AZO. X-ray diffraction spectra demonstrate preferential (002) crystallographic orientation having c-axis perpendicular to the surface of the substrate and average crystallites size of the films was about 33-54 nm. With increasing Al doping, AZO films have a strong improved crystalline quality. As compared to pure ZnO, Al-doped ZnO exhibited lower crystallinity and there is a shift in the (002) diffraction peak to higher angles. Due to the doping of Al of any concentration, the films were found to be showing [80 % transparency. As Al concentration increased the optical band gap was also found to be increase from 3.22 to 3.47 eV. The room-temperature photoluminescence spectra indicated that the introduction of Al can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects in UV optoelectronic devices. A detailed comparison and apprehension of electrochemical, optical and structural properties of ZnO and ZnO:Al thin films is done for the determination of optimum concentration of Al doping.
Al Doped ZnO Thin Films; Preparation and Characterization
2018
ZnO is a promising material suitable for variety of novel electronic applications including sensors, transistors, and solar cells. Intrinsic ZnO film has inferiority in terms of electronic properties, which has prompted researches and investigations on doped ZnO films in order to improve its electronic properties. In this work, aluminum (Al) doped ZnO (AZO) with various concentrations and undoped ZnO films were coated on glass substrates by a sol–gel spin coating technique. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Uv-Vis spectrometer and four point probe technique to investigate the structural, surface morphology, optical transmittance, and electronic properties of the thin films. The optical transmittances of these samples in the visible region are in the range of 85-95% and the SEM images showed the size of nanoparticles were decrease with doping. Also 2% Al doped ZnO thin films had a lowest resistivity of all the samples that prepa...
Keywords: Al–F co-doped ZnO Transparent conducting oxide (TCO) Thin film magnetron sputtering Substrate temperature a b s t r a c t ZnO is a wide bandgap semiconductor that has many potential applications such as solar cells, thin film transistors, light emitting diodes, and gas/biological sensors. In this study, a composite ceramic ZnO target containing 1 wt% Al 2 O 3 and 1.5 wt% ZnF 2 was prepared and used to deposit transparent conducting Al and F co-doped zinc oxide (AFZO) thin films on glass substrates by radio frequency magnetron sputtering. The effect of substrate temperatures ranging from room temperature (RT) to 200 • C on structural, morphological , electrical, chemical, and optical properties of the deposited thin films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Hall effect measurement, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and UV–vis spectrophotometer. The XRD results showed that all the AFZO thin films had a (0 0 2) diffrac-tion peak, indicating a typical wurtzite structure with a preferential orientation of the c-axis perpendicular to the substrate. The FE-SEM and AFM analyses indicated that the crystallinity and grain size of the films were enhanced while the surface roughness decreased as the substrate temperature increased. Results of Hall effect measurement showed that Al and F co-doping decreased the resistivity more effectively than single-doping (either Al or F doping) in ZnO thin films. The resistivity of the AFZO thin films decreased from 5.48 × 10 −4 to 2.88 × 10 −4-cm as the substrate temperature increased from RT to 200 • C due to the increased carrier concentration and Hall mobility. The optical transmittances of all the AFZO thin films were over 92% in the wavelength range of 400–800 nm regardless of substrate temperature. The blue-shift of absorption edge accompanied the rise of the optical band gap, which conformed to the Burstein-Moss effect. The developed AFZO thin films are suitable as transparent conducting electrodes for various optoelectronic applications.
Sol-gel Aluminum-doped ZnO thin films: synthesis and characterization
Sol-gel Aluminum-doped ZnO thin films: synthesis and characterization, 2017
Zinc oxide is one of the most important n-type semiconductor intensively utilized in solar cells, transparent conducting electrodes and opto-electronic devices. Zinc oxide (ZnO) and Aluminum-doped Zinc oxide (AZO) thin films have been deposited by the spin-coating method. Their structural, optical and electrical proprieties were investigated. The X-Ray diffraction shows the polycrystalline hexagonal wurtzite structure exhibiting degradation in crystallinity of elaborated films with increasing Al doping concentration. This effect is reflected on optical and electrical proprieties of films. Indeed, the samples present a low optical transmittance level and the band gap values between 3.17 eV and 3.20 eV. Concerning the electrical properties, a decrease in the concentration of free charges carriers is observed as well as a decrease in resistivity.
Effects of Al dopant on structural and optical properties of ZnO thin films prepared by sol-gel
Przegląd Elektrotechniczny, 2013
Transparent and conductive Al doped ZnO thin films were synthesized at room temperature by sol gel technique both pure ZnO and Al- doped(1,3,and5%) thin films were deposited on a glass substrate. The sols were prepared using zinc acetate dehydrate and aluminum chloride provides Al ions, played an important role in improvement of the c - axis, the structural characteristics have been studied by X-ray diffraction, and UV-Vis-NIR spectroscopy. The films are transparent from the near ultraviolet to the near infrared, SEM image also showed that the average grain size is decreased with increasing of Al concentration, band gap values of prepared thin films varied in the range of (3.18 - 3.42 eV). Streszczenie. Przejrzyste i przewodzące cienkie warstwy Al domieszkowane ZnO zostaly zsyntetyzowane w temperaturze pokojowej techniką zol- zel. Na podlozu szklanym naniesiono cienkie warstwy Al niedomieszkowanego oraz domieszkowanego ZnO w stosunku 1, 3, i 5%. Zole zostaly przygotowane wykorzystuj...
Journal of Crystal Growth, 2006
Transparent and conductive high-preferential c-axis-oriented Al-doped zinc oxide (ZnO:Al, AZO) thin films have been prepared by the sol-gel route. Film deposition was performed by spin-coating technique on Si(1 0 0) and glass substrate. Structural, electrical and optical properties were performed by XRD, SEM, four-point probe, photoluminescence (PL) and UV-VIS spectrum measurements. The effects of annealing temperature and dopant concentration on the structural and optical properties are well discussed. It was found that both annealing temperature and doping concentration alter the microstructures of AZO films. Also, PL spectra show two main peaks centered at about 380 nm (UV) and 520 nm (green). The variation of UV-to-green band emission was greatly influenced by annealing temperatures and doping concentration. Reduction in intensity ratio of UV-to-green might possibly originate from the formation of Al-O bonds and localized Al-impurity states. The minimum sheet resistance of 10 4 O/& was obtained for the film doped with 1.6 mol% Al, annealed at 750 1C. Meanwhile, all AZO films deposited on glass are very transparent, between 80% and 95% transmittance, within the visible wavelength region. These results imply that the doping concentration did not have significant influence on transparent properties, but improve the electrical conductivity and diversify emission features. r