Al Co-Doped ZnO Research Articles

Effect of Annealing Temperature on Optoelectronic Performance of F- and Al-codoped ZnO Thin Films for Photosensor Applications

Effect of Annealing Temperature on Optoelectronic Performance of F- and Al-codoped ZnO Thin Films for Photosensor Applications

Enhancing Optical and Electrical Properties of La- and Al-Codoped ZnO Thin Films Prepared by Sol-Gel Method -La Codoping Effect

This work focuses on the fabrication and potential application of the various cation-doped ZnO materials in recent patents and literature and then presents the La codoping effects of Al-doped ZnO films. Films were deposited by a sol-gel route and characterized by various techniques including X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis and luminescent spectroscopies, and electrical conduction analysis. The UV-vis. transmittance and band gap increased and then decreased, whereas the resistivity decreased and then slightly increased with the increase in La/Al ratio. The La/Al ratio of 0.0105 led to a maximal transmittance, a widest band gap, and a minimal resistivity. The films also illustrated a near band gap emission and some intrinsic defect-related emissions with varied intensity with La/Al ratio. This work reveal that the electrical and optical properties of the ZnO:Al films can be well enhanced by La codoping. This is significant to the applications of the ZnO:Al materials.

Characterization of F- and Al-codoped ZnO Transparent Conducting Thin Film prepared by Sol-Gel Spin Coating Method

ZnO thin film co-doped with F and Al was prepared on a glass substrate via simple non-alkoxide sol-gel spin coating. For a fixed F concentration, the addition of Al co-dopant was shown to reduce the resistivity mainly due to an increase in electrical carrier density compared with ZnO doped with F only, especially after the second post-heat-treatment in a reducing environment. There was no effective positive contribution to the reduction in resistivity due to the mobility enhancement by the addition of Al co-dopant. Optical transmittance of the ZnO thin film co-doped with F and Al in the visible light domain was shown to be higher than that of the ZnO thin film doped with F only.

Transparent Conductive and Wide Band Gap Characteristics of Quaternary Mg and Al Co-Doped ZnO Thin Films Prepared by Radio Frequency Sputtering Method

Transparent Conductive and Wide Band Gap Characteristics of Quaternary Mg and Al Co-Doped ZnO Thin Films Prepared by Radio Frequency Sputtering Method

Influence of Al concentration and annealing temperature on structural, optical, and electrical properties of Al co-doped ZnO thin films

The pure ZnO and Al-doped ZnO (AZO) thin films (thickness: 200nm) were prepared on both side polished silica (SiO2) substrates via RF magnetron sputtering at room temperature by using 2.5 inches high-purity ZnO (99.9%) and Al (99.9%) targets. The samples were annealed at 300°C, 400°C and 500°C for 45min in N2 ambient in quartz annealing furnace system, respectively. We investigated the effects of various Al concentrations and annealing treatment on the structural, electrical, and optical properties of films. The preferred crystallization was observed along c axis (single (002) diffraction peak) from substrate surface assigning the single crystalline Würtzite lattice for pure ZnO and AZO thin films. Although increasing Al concentration decreases the order of crystallization of as-grown films, annealing process increases the long range crystal order. The crystallite sizes vary between minimum 12.98nm and maximum 20.79nm for as-grown and annealed samples. The crystallite sizes decrease with increasing Al concentration but increase with increasing annealing temperature as general trend. The grain size and porosity of films change with annealing treatment. The smaller grains coalesce together to form larger grains for many films. However, a reverse behavior is seen for Al2.23ZnO and Al12.30ZnO samples. That is, Al concentration plays critical role as well as temperature on grain size. Low percent optical transmittance (T%) is observed due to higher Al concentration and worse crystal quality for as-grown AZO films. T% decreases until 34.5% for as-grown Al15.62ZnO film. T% increases by increasing annealing temperature. AZO samples annealed at 500°C have around 80% transparencies in the visible range of spectrum. Optical energy band gap values range between 3.17eV and 3.60eV for as-grown and annealed samples. Band gap increments are attributed to increasing free electron concentration depending on doped Al ratio known as Burstein–Moss effect. Annealing process increases the band gap values, too. The electrical conductivity and carrier concentration of the films increased with increasing Al content. The mobility decreases due to increase in Al concentration that deteriorates the crystal nature. Annealing process especially at 400°C enables the AZO samples to exhibit best electric conductivity due to long range crystal structured nature and increasing free electron concentration in the films. The maximum electrical conductivity value of 1.06×104(Ωcm)−1 was measured from Al12.30ZnO sample annealed at 400°C.

Structural and Optical Characterization of Ni and Al Co-Doped ZnO Nanopowders Synthesized via the Sol-Gel Process

We have successfully synthesized (Ni,Al) co-doped ZnO nanostructured powders via the sol-gel technique at low temperature. The elemental analysis confirms the incorporation of the Ni and Al ions into the ZnO matrix. The structural study revealed that the nanopowder samples are assembled in flower-shaped Zn 0.9-xNi0.1AlxO nanostructures with average crystallite sizes ranging from 39 to 53 n m. The XRD patterns show that the Zn0.9-xNi0.1AlxO nanopowders have a hexagonal wurtzite polycrystalline structure. Weak diffraction peaks related mainly to nickel oxides are also detected in the samples. The highest crystallite size, lowest lattice parameters and unit cell volume are obtained for the nanopowder samples that contain 1.5 at.% of aluminum. The decomposition process of the dried gel system is investigated by thermogravimetric analysis (TGA). Raman scattering and FT-IR measurements confirm the wurtzite structure of the synthesized Zn 0.9-xNi0.1AlxO nanopowders. The energy band gap of the synthesized nanopowders (~3.32 eV ) was estimated by using the Brus equation and the crystallite sizes obtained from XRD data, for comparison. The strain in the nanopowder samples (~2.7 × 1 0 –3 ) was also calculated according to the Stokes-Wilson equation.

Effects of Ga- and Al-Codoped ZnO Buffer Layer on the Performance of Inverted Polymer Solar Cells

A Ga, Al-doped zinc oxide (GAZO) buffer layer was applied to inverted polymer solar cells (PSCs) based on P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C61-butyric acid methyl ester] blend films. The work function of the GAZO layer on indium-tin oxide (ITO) was measured to be 4.45 eV. The insertion of the GAZO layer between the ITO electrode and the P3HT:PCBM blend film in the inverted PSC led to an improved short-circuit current (Jsc), open-circuit voltage (Voc) and fill factor (FF) compared to those of the reference cell without GAZO layer. The Jsc enhancement in the inverted PSC with the GAZO layer was attributed to both the effective electron extraction and the increased crystallinity of P3HT, and the work function difference between Ag and GAZO layer induced the increase in Voc. The improved FF value was due to the lowered series resistance and elevated shunt resistance. Thus, the power conversion efficiency of the device with the GAZO layer was improved by more than 200% relative to the reference cell.

Effect of Direct Current Power to Ti-Target on the Composition, Structure and Characterization of the Ti (0–2.36 at. %), Al Codoped ZnO Sputtering Thin Films

Transparent conductive Ti, Al codoped ZnO (TAZO) films were prepared on glass substrate by three-target magnetron sputtering system in this work. The glass substrate was heated to 200 °C, and the working pressure in the chamber was at 5×10-2 Torr. In the process of sputtering, pure Ti target was bombarded by direct current varying in the power at 0, 20, 30, and 40 W; however, the pure Al target and pure ZnO target were bombarded by radio frequency power fixed at 100 W. After sputtering for 150 min, the thickness of the films was measured to be about 700 nm varying in Ti-content. The surface morphology and cross section of the films were examined by using field emission scanning electron microscope (FE-SEM) and their composition was analyzed with attached energy dispersive spectroscopy (EDS). The Ti-content of the films was found to increase with increasing the DC power in the order: 0 at. % (0 W) < 0.59 at. % (20 W) < 1.35 at. % (30 W) < 2.36 at. % (40 W). Analysis of X-ray diffraction (XRD) indicated that all the films belong to wurtzite structure textured on (0002). Through examination by atomic force microscopy (AFM), the films revealed their average surface roughness (Ra) decreased from 10.74 to 5.40 nm with increasing the Ti-content. Surface composition and depth profile of the films were examined by X-ray photoelectron spectroscopy (XPS). The electrical resistivity of the films, determined by four-point probe, was in the range from 0.93×10-3 Ω cm (with 0.59 at. % Ti) to 8.34×10-3 Ω cm (with 2.36 at. % Ti). The average optical transmittance of the films analyzed by UV–vis light was higher than 85% in visible spectra.

Effects of Codoping Al3+ on Luminescence of ZnO: Eu and ZnO:Tb Thin-Films

Rare-earth (RE = Eu, Tb) doped ZnO and Al-codoped ZnO:RE films on silicon wafers were prepared by sol-gel techniques and subsequently annealed in argon ambient. The films were characterized by photoluminescence spectroscope, Raman spectroscope and scanning electron microscope. When doped with RE only, the most intense lines of RE emissions were observed in ZnO nanofilms doped with RE at a concentration of 1%. Al-codoping into the ZnO:RE nanofilms could obviously improve the efficiencies of the RE emissions. The RE emission intensities depended on Al concentration. The improvement of the RE emissions could be attributed to the defects and crystallizations caused by Al codoping in the ZnO:RE nanofilms.