Al-doped ZnO Research Articles

X-ray peak broadening and strain-driven preferred orientations of pure and Al-doped ZnO nanoparticles prepared by a green gelatin-based sol-gel method

Al-doped ZnO nanoparticles (Zn1-xAlxO, x = 0 ∼ ZnO; x = 0.01 ∼ ZA1; x = 0.03 ∼ ZA3; x = 0.05 ∼ ZA5) were prepared by a gelatin-based sol-gel method. The structure of the prepared samples was examined by X-ray diffraction (XRD) and field emission electron microscopy (FESEM). The results showed a hexagonal structure and spherical shape for the samples. The XRD results were analyzed by size strain plot (SSP), and it was obtained that the crystallite size decreases as the Al concentrations increase. In addition, the lattice strains (ε), Young's module (Y), and Poison ratio (ν) were calculated for each crystal lattice direction. The results indicated that the lattice strains show similar behavior for samples with different amounts of Al in each direction. Elemental analysis and combinations of binding energies were carried out by Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results prove the participation of the aluminum atom in the zinc oxide network.

Investigation of Site Dependent Donor-Acceptor (Al-N) Doping Effect into ZnO for Optoelectronic Applications

In this study, the density functional theory (DFT) is used to investigate the effect of the incorporation of Al (donor) in the Zn-site and N (acceptor) in the O-site of ZnO. The detailed theoretical study highlights the confirmation of p-type conductivity and bandgap (0.58 and 0.21 eV) narrowing exhibits in N- and (Al-N)-doped ZnO systems. p-type nature is explicitly observed by introducing acceptor bands at the top of the valance band (VB). Whereas, degenerate n-type conductivity is seen in Al-doped ZnO and a widened bandgap of 2.70 eV is attributed to Burstein-Moss (BM) effect. The calculated value of the effective mass of the (Al-N)-doped ZnO system is lower than that of the un-doped ZnO. Enhancement of the absorption and photoconductivity in the visible region for N- and (Al-N)-doped ZnO could be due to the availability of more density of states. Importantly, reflectivity, refractive index, transmittance, dielectric constants, and optical band gap have also been calculated. Higher transmittance of the samples suggested that these could be suitable for the window material of solar cells. The optical bandgap value supports the electronic bandgap value. Therefore, our finding would be helpful to design high-performance homo-junction based electronic and optoelectronic devices.

Antimicrobial activities and neuroprotective potential for Alzheimer’s disease of pure, Mn, Co, and Al-doped ZnO ultra-small nanoparticles

Antimicrobial activities and neuroprotective potential for Alzheimer’s disease of pure, Mn, Co, and Al-doped ZnO ultra-small nanoparticles

Al-doped ZnO Thin Films via Sputtering: Influence of Structural Defects on Ozone Gas Sensitivity

Al-doped ZnO Thin Films via Sputtering: Influence of Structural Defects on Ozone Gas Sensitivity

High-Performance UV Detector Using Al-Doped ZnO Phototransistor Prepared by Initiated-CVD Doping Technique

High-Performance UV Detector Using Al-Doped ZnO Phototransistor Prepared by Initiated-CVD Doping Technique

A numerical investigation for performance enhancement of organic solar cell using Al-doped zinc oxide anode

A numerical investigation for performance enhancement of organic solar cell using Al-doped zinc oxide anode

Enhanced Thermoelectric Performance in n-type Al-doped ZnO in the Form of (Zn1-x Alx)O

Compositions of (Zn1-xAlx)O were synthesized via the Solid-state reaction (SSR) technique at 1000 oC , with x ranging from 0.0005 to 0.03. After the preparation of the sample, the structure and thermoelectric properties were examined by XRD, SEM, and EDX and the home-built equipment, respectively. All the samples are observed to be polycrystalline and hexagonal structures. The composition with ( x= 0.015), i.e. (ZnO0.985Al0.015), exhibited the highest electrical conductivity values of 5500 S/m at 580 K. As well as for the Seebeck coefficient, it was discovered that the composition (ZnO0.98Al0.02) ) had the highest values of 400 mv/K at 680. The power factor (PF) for the composition with the formula ( ZnO0.98Al0.02)) was found to have the most outstanding possible value of 1300 mw/mK2 at 850 K.

Modification in structural, electrical and defect luminescence properties of ZnO nanorod films with Cu, Al and double-doping

Zinc oxide nanorods have broad application prospects in the field of photoelectric devices. However, the application as photodetectors in the visible light band is limited by their narrow luminescent spectrum and poor electrical conductivity. In this work, three different zinc oxide nanorod films respectively with Cu, Al and double-doping have been prepared for investigating the modifying effect of their defect luminescence and electric performance. In this paper, Cu doped zinc oxide with rod structure and Al doped zinc oxide with flaky structure are fabricated by hydrothermal method and sol-gel method, respectively. As for the double-doping, Al doped zinc oxide films are grown on the surface of Si by sol-gel method, and Cu doped zinc oxide nanorods are grown on the surface of Al doped zinc oxide films by hydrothermal method. The results show that the Cu doping can improve the number of defects, leading to the electrons transport from VZn to Zni and then releasing the photons. Alternatively, the trivalent aluminum ions exist in zinc oxide nanorods in the form of replacement or gap, increasing the carrier concentration, turn-on voltage and rectification ratio of zinc oxides. As for the Cu–Al double-doping, Al doped zinc oxide films are located between Cu doped zinc oxide nanorods and Si substrate and work as an intermediate layer of current. Trivalent aluminum ions can change the semiconductor properties of zinc oxide and make it have the performance of p-type semiconductor which can improve the electrical properties of zinc oxide semiconductor. Besides, the carrier concentration of Cu–Al double-doping zinc oxide is nearly 3 times higher than that of pure one. Increasing the carrier concentration can increase the current of ZnO–Si heterojunction in the dark, thus improving the photoelectric properties of ZnO nanorods.

Microstructure and thermoelectric properties of pristine and Al-doped ZnO ceramics fabricated by cost-effective and eco-friendly wet chemistry methods

ZnO has potential as a thermoelectric material for high-temperature applications, but its performance is limited by the strong interconnection between electrical and thermal transportation. In this study we proved that ZnO bulk samples produced from cost-effective and environmentally friendly nitrates via ultrasonic spray pyrolysis and modified chemical precipitation methods followed by spark plasma sintering, demonstrate significantly higher thermoelectric performance than those fabricated from commercially available ZnO powder. To further explore the potential of the developed chemical precipitation technique, we synthesized a series of Al-doped samples with a nominal composition of Zn1–xAlxO (x = 0.02, 0.04, 0.06). The substitutuion of Al into the ZnO structure led to two significant effects: (i) a partial substitution of Zn with Al boosts the power factor; (ii) the formation of the ZnAl2O4 spinel phase acting as scattering center for phonons in addition to the mass and strain fluctuations induced by the partial Zn-Al substitution, both leading to the thermal conductivity reduction. As a result, Al doping led to a threefold enhancement of the thermoelectric performance with zT value of ∼0.12 achieved at 1100 K for the Zn0.94Al0.06O sample.

Electrostatic Spray Deposition of Al-Doped ZnO Thin Films for Acetone Gas Detection

In this study, pure ZnO and Al-doped ZnO(AZO) thin films were coated onto a SiO2 wafer using the electrostatic spray deposition (ESD) process for acetone gas detection under laboratory conditions. Voltage levels were varied to determine the optimal conditions for producing thin films with the highest uniformity. The results indicate that the optimal coating voltage for achieving the highest uniformity of the coated films is 2.9 kV for ZnO and 2.6 kV for AZO. The thin films were produced under these optimal ESD conditions by adjusting the coating time, and gas sensors were fabricated by printing electrodes using a reverse offset process on top of the thin films. Analysis of the sensing response revealed that the AZO-coated gas sensor with a 200 s deposition exhibited the best acetone-sensing ability at 300 °C, with a maximum response of 13.41 at 10 ppm. Furthermore, the fabricated gas sensors effectively detected acetone gas even at a low concentration of 2 ppm, demonstrating high selectivity in comparison to other gases.

COMPARATIVE PERFORMANCE ANALYSIS OF SOL–GEL METHOD AND HYDRO THERMAL METHOD FOR ZINC OXIDE NANOPARTICLE SYNTHESIS

Nanomaterials have emerged as an amazing class of materials that consists of a broad spectrum of examples with at least one dimension in the range of 1 to 100 nm. Exceptionally high surface areas can be achieved through the rational design of nanomaterials. Nanomaterials can be produced with outstanding magnetic, electrical, optical, mechanical, and catalytic properties that are substantially different from their bulk counterparts. There has been considerable focus on the synthesis of metal nanoparticles with distinct and exceptional characteristics, making it a highly captivating area of research. Among these nanoparticles, Zinc Oxide NanoParticles (ZnO NPs) have gathered significant attention in the field of bioengineering. Various approaches have been explored for the preparation of ZnO nanoparticles. In this paper we are comparing two synthesis methods as Sol–Gel Method and Hydro Thermal Method for Zinc Oxide Nanoparticles. Sol-gel method based ZnO nanoparticles are compared with Hydrothermal based ZnO nanoparticles in terms of XRD, UV Visible Spectrum and SEM analysis. Sol-gel method based Al-doped Zinc Oxide Nanoparticle (AZnO) is compared with Hydrothermal based Al-doped Zinc Oxide Nanoparticle (AZnO) in terms of XRD, UV Visible Spectrum, SEM analysis and optical properties. At last Sol-gel method based Au-doped ZnO- Sm (NO3)3 is compared with Hydrothermal based Au-doped ZnO nanoparticles in terms of optical properties as transmittance and absorbance, structural properties as XRD analysis. From this paper we can conclude that, Sol-gel method based Au doped ZnO nano particles are efficient than Hydro thermal based ZnO nano particles.

Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are -0.56 eV and -0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching -1.64 eV, -1.69 eV, and -3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

SYNTHESIS AND CHARACTERIZATION OF Al-DOPED ZnO THIN FILMS AS ANTI-REFLECTION COATINGS FOR SOLAR CELL APPLICATIONS

In this work, we have synthesized ZnO:Al thin films by pulsed laser deposition technique and investigated their microstructural and optical properties. The XRD study confirmed a polycrystalline structure of wurtzite ZnO in all films. Further, Al doping has improved the crystallinity and decreased the crystal size and volume of the unit cell. The surface morphology was homogeneous with nanoscopic crystals clustered to form granular nanoparticles. The optical properties significantly improved by increasing the Al doping concentration. The produced thin films are excellent candidates for use as an anti-reflection layer in solar cells due to their outstanding properties.

The study of optical-electrical properties of ZnO(AZO)/Si heterojunction

In this paper, zinc oxide (ZnO) thin films and Al-doped zinc oxide (AZO) films are prepared. The XRD results show that the addition of Al ions at the middle stage of AZO film (ms-AZO) preparation can increase the grain size and change the preferential growth orientation from (100) crystal plane to (002) crystal plane. The results of UV-VIS spectra show that the addition of Al ions at the ms-AZO preparation can greatly increase the absorption intensity in the visible light region, and the addition of Al ions at the early stage of AZO film (es-AZO) preparation can make the blue shift of the ultraviolet absorption edge. The patterns of I–V curves show that the addition of Al ions can increase the forward current of AZO/Si heterojunction, comparing to that of ZnO/Si heterojunction. Furthermore, the leakage current mechanism may dominate the carrier transport.

Excellent crystalline silicon surface passivation by transparent conductive Al-doped ZnO/ITO stack

The surface passivation materials commonly used in crystalline silicon (c-Si) solar cells are either electrically insulating or opaque to the solar spectrum, which poses the electrical loss or optical loss. Hence it is of great significance to explore functional films that are simultaneously transparent, conductive and passivating for c-Si. In this study, we successfully tune two most well-known transparent conductive oxides, i.e. Al-doped ZnO (AZO) and indium tin oxide (ITO), as excellent passivation layers for c-Si surface. The AZO film is grown by atomic layer deposition and is capped with a magnetron-sputtered ITO film. Dynamic secondary ion mass spectrometry reveals that such stack design can retain higher hydrogen concentration on c-Si surface than a single AZO film during annealing. In addition, the AZO should be highly doped to reduce the energy barrier height around c-Si surface, thereby increasing the charge carrier asymmetry and thus reducing surface recombination. It is also highly crucial to optimize the annealing temperature and interfacial silicon oxide. As such, the effective minority carrier lifetime reaches 2.0 ms and the implied open-circuit voltage approaches 700 mV. Besides, the AZO/ITO stacked films possess negligible optical absorption, low sheet resistance (∼90 Ω/sq), and outstanding antireflection effect on c-Si surface.

Multifunctional Al-doped ZnO thin films for vertically aligned liquid crystal devices

The integration of ITO-free transparent conductive layers remains a big challenge for development of next generation technologies. Here, we demonstrate the feasibility of transparent and conductive Aluminum-doped Zinc Oxide (AZO) thin films to operate simultaneously as electrode and alignment layer in Liquid Crystal (LC) device configuration. Controlling the growth process of AZO thin films by Atomic Layer Deposition (ALD) technique results of predominantly (100) crystallographic oriented AZO with very high transparency and excellent conductivity. The exceptionally low surface free energy of (100) oriented AZO, along with the topological modification following the mechanical rubbing treatment were used to elucidate the mechanism of LC molecules alignment on the surface of AZO film. The uniform vertical orientation of the nematic LC director was confirmed by polarized optical microscopy and pretilt angle measurements. The competitive electro-optical performance in terms of phase modulation, threshold and saturation voltages and contrast ratio of the assembled LC device reveals the great potential of AZO thin films as transparent electrode and alignment layer for future LC display applications with versatile functionality.

Engineering the visible light absorption of one-dimensional photonic crystals based on multilayers of Al-doped ZnO (AZO) thin films

Engineering the visible light absorption of one-dimensional photonic crystals based on multilayers of Al-doped ZnO (AZO) thin films

Improving FTO/ZnO/In2S3/CuInS2/Mo solar cell efficiency by optimizing thickness and carrier concentrations of ZnO, In2S3 and CuInS2 thin films using Silvaco-Atlas Software

Optimization of optical and electrical properties of active semiconducting layers is required to enhance thin film solar cells' efficiency and consequently became the cornerstone for sustainable energy production. Computational studies are one of the ways forward to optimize solar cells’ characteristics. In this study, Silvaco-Atlas, a powerful software that excels in both 2D and 3D electrical simulations of semiconductors has been used for the simulation in order to investigate the solar cell properties. The architecture of the solar cell simulated was FTO/ZnO/In2S3/CuInS2/Mo. This study aims to optimize solar cell efficiency by optimizing film thicknesses and carrier concentrations via simulation. The designed solar cell was exposed to the presence of a sun spectrum of AM1.5 from a 1kW/m2 incident power density at 300K. The thickness values of the window (ZnO), absorber (CuInS2) and buffer (In2S3) layers were varied to record a solar cell's optimum thickness. The resulting FTO/ZnO/In2S3/CuInS2/Mo solar cell formed by simulation is presented. The best efficiency and fill factor of the solar cell simulated were found to be 41.67% and 89.19%, respectively. The recorded values of current density and the open circuit voltage of the cell were 40.33mA/cm2 and 1.15 V, respectively. Additionally, the maximum power of the simulated solar cell device was 41.68 mW. Optimization results revealed that the most efficient cell found was made up of a window layer with a thickness of 0.03μm, an absorber layer with a thickness of 6.0μm and a buffer layer with a thickness of 0.2μm. The optimized carrier concentration of ZnO, In2S3 and CuInS2 was respectively 1e21 cm-3, 1e20 cm-3, 3e18 cm-3 and the optimized Al-doped ZnO value was 1e25 cm-3. The Absorption spectra indicated that the solar cell's peak absorption occurs between 350 nm and 1250 nm and presented a good external quantum efficiency (EQE) of around 84.52% to 92.83% which indicates good efficiency in the visible domain. This performance is attributed to the transparency of FTO, ZnO and good absorption of In2S3 and CuInS2 thin films.

Solar photodegradation of malathion from aqueous media using Al-doped ZnO/Fe3O4 nanocomposite

This study was conducted to boost the photocatalytic activity of ZnO by using Al:ZnO/Fe3O4 (MAZ) nanocomposite. Al-doped ZnO (Al:ZnO) nanoparticles and MAZ nanocomposite were synthesized using hydrothermal, chemical precipitation, and reflux methods. The most optimal nanomaterials in terms of characterization and photocatalytic degradation efficiency were 1.0 wt% MAZ and 1.0 wt% Al:ZnO, respectively. The suitable degradation efficiency by 2.0 g/L of 1.0 wt% MAZ nanocomposite and 1.0 wt% Al:ZnO nanomaterials under sunlight illumination and a duration of 180 min for the concentration of 50 mg/L malathion, was equal to 82 and 80%, respectively.

Study of time-resolved photoluminescence decay curves in Al-doped ZnO and Eu-doped Cd1−xZnxS nanophosphors

Study of time-resolved photoluminescence decay curves in Al-doped ZnO and Eu-doped Cd1−xZnxS nanophosphors