Al ZnO Research Articles

Investigations of adsorption and photoluminescence properties of encapsulated Al–ZnO nanostructures: Synthesis, morphology and dye degradation studies

This study focuses on the solution combustion approach to examine the nanostructures of undoped and doped ZnO with different concentrations of Al (0.1 % and 0.2 %). Various physical techniques were utilized to characterize the synthesized nanoparticles. X-ray diffraction (XRD) revealed the crystalline materials, while scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) findings confirmed the products with particle size and the insertion of Al into the ZnO lattice. Fourier-transform infrared spectra (FTIR) confirmed the presence of different functional groups in the obtained material. The results indicate that Al-doped ZnO (Al–ZnO) nanoparticles show promising properties for optoelectronics and photoluminescence. Photoluminescence analysis indicated that an increase in Al3+ (0.2 %) concentration resulted in a decrease in peak intensity and an increase in the full width at half maximum. The band gap was calculated using the Taucs plot. The study also highlights the effectiveness of Zn1-xAlxO nanostructures in degrading organic pollutants, particularly in adsorbing Malachite Green (MG) dye. Among the samples, the 0.2 % Al-doped ZnO exhibited superior dye degradation efficiency due to its enhanced adsorption capacity and smaller particle size, as evidenced by multilayer adsorption capacity and chemisorption during the degradation process. This study provides valuable insights into the potential applications of Al-doped ZnO nanoparticles in various environmental and technological fields, emphasizing their significance in the degradation of organic pollutants.

Understanding of the Relationship between the Properties of Cu(In,Ga)Se2 Solar Cells and the Structure of Ag Network Electrodes

The relation between the structure of the silver network electrodes and the properties of Cu(In,Ga)Se2 (CIGS) solar cells is systemically investigated. The Ag network electrode is deposited onto an Al:ZnO (AZO) thin film, employing a self‐forming cracked template. Precise control over the cracked template's structure is achieved through careful adjustment of temperature and humidity. The Ag network electrodes with different coverage areas and network densities are systemically applied to the CIGS solar cells. It is revealed that predominant fill factor (FF) is influenced by the figure of merit of transparent conducting electrodes, rather than sheet resistance, particularly when the coverage area falls within the range of 1.3–5%. Furthermore, a higher network density corresponds to an enhanced FF when the coverage areas of the Ag networks are similar. When utilizing a thinner AZO film, CIGS solar cells with a surface area of 1.0609 cm2 exhibit a notable performance improvement, with efficiency increasing from 10.48% to 11.63%. This enhancement is primarily attributed to the increase in FF from 45% to 65%. These findings underscore the considerable potential for reducing the thickness of the transparent conductive oxide (TCO) in CIGS modules with implications for practical applications in photovoltaic technology.

Versatile r.f. magnetron sputtering doping method to produce aluminum‐doped zinc oxide films

AbstractAluminum‐doped zinc oxide Al:ZnO (AZO) is a non‐toxic material applied as a transparent conductive oxide film. In this study, we report on the structural, optical, and electrical properties of AZO films obtained by thermally oxidizing aluminum‐doped Zn films produced by a versatile and low‐cost method of doping using the magnetron sputtering technique deposition. We use aluminum wire above the zinc target to produce Al:Zn films. The influence of r.f. power and different Al wire lengths on the AZO film properties were studied. The resulting AZO films exhibited Al concentrations of up to 2.85% and an optical gap between 3.22 and 3.29 eV. The transmittance was greater than 80% for all samples, and the electrical resistivity decreased by two orders of magnitude with Al doping. As a result, the sample with an aluminum concentration of approximately 1% had the lowest resistivity. In this work, it was possible to relate the lower resistivity with larger grain size and smaller concentrations of defects or vacancies.

Elucidating the Potential Strategies for Performance Improvement of CBTSSe‐Based Solar Cells: A Pathway Toward 20% Efficiency

Cu2BaSnS4−xSex (CBTSSe) has recently attracted substantial attention as an emerging chalcogenide material due to its abundant constituent elements and reduced antisite disorders compared to the Cu2ZnSn(S,Se)4 (CZTSSe). In this work, recently reported Mo/CBTSSe/Cd:ZnS Zn1−xCdxS/i‐Mg:ZnO (ZMO)/Al:ZnO (AZO) cell structure with the power conversion efficiency (PCE) of 6.17% is used to develop the baseline model. Afterwards, device performance parameters are fine‐tuned by investigating the effect of (a) absorber thickness and defect density, (b) absorber/buffer conduction band offset, (c) absorber/buffer interface defect density, (d) anti‐reflection coating at the front layer, and (e) back contact optimization. The device with the optimized parameter values of absorber thickness: 1.2 μm, absorber defect density: 1015 cm−3, and alternate buffer layer of WS2, interface defect density:1010 cm−2, resulting in the PCE of 12.94%. Introducing an anti‐reflective coating (ARC) at the front contact further improves the PCE to 17.87%. Finally, introducing Ni as a back contact instead of Mo enhances the PCE to 20.70%. These results provide insight into possible techniques to improve the performance of CBTSSe‐based solar cells.

Hybrid surface wave propagation through the interface of semiconductor and metal waveguide

Hybrid surface wave propagation through the interface of semiconductor and metal waveguides consisting of CuO/Al and ZnO/Al have been investigated by numerical simulation due to their potential applications. COMSOL Multiphysics is used to simulate the waveguides by adjusting model properties. For the comparative study, the propagation constant (γ), normalized phase (β), attenuation constant (α), propagation length (L), total electric and magnetic energy propagated through the CuO-based Al waveguides and ZnO based Al waveguide is discussed. Comparative studies for both modifications were performed from 0 THz to 12 THz. This study employed boundary conditions to have the continuous behavior of the electric field component of hybrid surface waves (exhibits characteristics of both transverse waves and longitudinal waves) at the interface between metal and semiconductor. The ZnO-based modification shows a higher propagation constant (γ) at all frequencies. Similar trends are observed for propagation length (L) and propagation constant (γ). Meanwhile, the attenuation constant (α) of the CuO-based Al waveguide is higher than that of the ZnO-based Al waveguide. An identical trend was perceived for both electrical and magnetic energy. Maximum parameters favour the ZnO-based Al waveguide, which makes it superior to the CuO-based Al waveguide for high-frequency applications.

Polarization-sensitive UV detector based on a double-layer subwavelength grating of Al and ZnO

Polarization-sensitive detectors are of great importance in the fields of remote sensing and imaging, environmental monitoring, and medical diagnosis. The surface plasmon effect can the enable polarization sensitivity of photodetectors through metallic gratings. However, limited by the precision of the nano-fabrication process, it is difficult to fabricate an ultraviolet (UV) polarization-sensitive detector integrated with sub-wavelength metal gratings and the polarization extinction ratio is relatively low. In this paper, an Al–ZnO composite double-layer grating structure was designed. The ZnO active layer and the Al layer were both fabricated into same-sized grating structures. Through this design, the slit width could be enlarged to some degree, while the response to 90° polarized light remained low. It is beneficial to realize a high polarization ratio and to spare the need for rigid fabrication accuracy. In addition, the influence of the structural parameters of the grating on the performance of the detector was studied by simulation. It was found that the resonance wavelength can be adjusted by changing the slit width and grating height, respectively. This provides a useful means for polarization-sensitive detection in different wavelength ranges. The polarization extinction ratio of the detector with a double-layer composite grating can reach 52 in the UV band (365 nm). This provides a good alternative to replace the traditional framework relying on the combination of polarizers and detectors. Moreover, it is a promising structure for high-density integrated photodetectors and imaging chips in the future.

Functional properties of transparent Al, Mg-doped and Al-Mg co-doped ZnO nanostructures grown by electrochemical and chemical bath deposition: a comparative study

Functional properties of transparent Al, Mg-doped and Al-Mg co-doped ZnO nanostructures grown by electrochemical and chemical bath deposition: a comparative study

Realization of Al:ZnO (AZO)-Ag nanocomposite as a novel photocatalyst capable of broadband photon harnessing driven by near-infrared plasmonics

The rising level of environmental pollution is a global concern and towards its mitigation, infrared photocatalysis emerges as a new concept, as the solar radiation at the earth’s surface has over 50% energy distribution in the near infrared (NIR) region. Al-doped ZnO (AZO) is a non-toxic congener of indium tin oxide (ITO) as transparent conducting oxide (TCO). A TCO-metal framework is developed as AZO-Ag@AZO nanocomposite by pulsed DC/DC magnetron sputtering. The consequences of diverse process conditions, viz, doping level, sputtering pressure, deposition time, and Ag/AZO co-sputtering time are noteworthy as the morphological, compositional, optical, and electrical properties are critically dependent on the process conditions. The structural and compositional analyses confirm wurtzite AZO and f.c.c. Ag with nanosized crystalline domains. A series of photocatalysis experiments reveal the significance of NIR plasmonics of AZO, realized by nanostructuring and generating optimum electron density (∼1020 cm−3). Notably, the optimal degradation rate (95%) of R6G is attained with tailored AZO-Ag@AZO nanocomposite. The gravity of visible surface plasmon resonance (SPR) due to Ag nanocrystallites and electron-hole pair creation in AZO cannot be undermined due to the remarkable participation of energetic electrons, and holes in redox reactions in harmony with actions of NIR SPR driven lower energy electrons.

A structural, optical and electrical comparison between physical vapour deposition and slot-die deposition of Al:ZnO (AZO)

Aluminium-doped zinc oxide (AZO) is a potential low-cost alternative to indium tin oxide (ITO) for application in optoelectronic devices as a transparent conducting thin film. Typically, AZO thin films are deposited using expensive, high vacuum equipment with high energy cost and materials wastage. In this study, slot-die coating was used as an inexpensive alternative to vacuum deposition to form AZO nanoparticle thin films under ambient laboratory conditions. The films were characterised structurally, optically and electrically and compared with a commercially obtained AZO film fabricated using physical vapour deposition (PVD). Structural characterisation of the nanoparticle film shows uniform coverage across the substrate with increased crystal quality following annealing in Ar up to 500 ^{circ }C. The optical properties of the nanoparticle film exhibit a wider band gap than the PVD film, while the high density of grain boundary defects between the nanoparticles inhibits sheet conductivity.Graphical abstract

Study of Gallium-Doped Zinc Oxide Thin Films Processed by Atomic Layer Deposition and RF Magnetron Sputtering for Transparent Antenna Applications.

Gallium-doped zinc oxide (GZO) films were fabricated using RF magnetron sputtering and atomic layer deposition (ALD). The latter ones demonstrate higher electrical conductivities (up to 2700 S cm-1) and enhanced charge mobilities (18 cm2 V-1 s-1). The morphological analysis reveals differences mostly due to the very different nature of the deposition processes. The film deposited via ALD shows an increased transmittance in the visible range and a very small one in the infrared range that leads to a figure of merit of 0.009 Ω-1 (10 times higher than for the films deposited via sputtering). A benchmarking is made with an RF sputtered indium-doped tin oxide (ITO) film used conventionally in the industry. Another comparison between ZnO, Al:ZnO (AZO), and Ga:ZnO (GZO) films fabricated by ALD is presented, and the evolution of physical properties with doping is evidenced. Finally, we processed GZO thin films on a glass substrate into patterned transparent patch antennas to demonstrate an application case of short-range communication by means of the Bluetooth Low Energy (BLE) protocol. The GZO transparent antennas' performances are compared to a reference ITO antenna on a glass substrate and a conventional copper antenna on FR4 PCB. The results highlight the possibility to use the transparent GZO antenna for reliable short-range communication and the achievability of an antenna entirely processed by ALD.

Machine learning analysis on critical structural factors of Al:ZnO (AZO) films

Machine learning (ML) has been recently approved to generalize materials design insights from many narrow-scoped individual experiments. In this study, decision tree algorithm (DT) was able to clarify critical structural factors enabling Al-doped ZnO (AZO) films with wider (or narrower) energy band gap and higher (or lower) electrical resistivity on published literature data as well as having ∼90 % average prediction accuracy. Cost-effective alternative of expensive physical models and simulations to reveal promising AZO films before physical experiments. Trained DTs were interpreted to uncover critical design insights. It was concluded that all microstructural features (crystalline size, crystallinity, dislocation density and interlamellar spacing) should be considered simultaneously through a holistic perspective in a design proposal. Al doping concentration and film thickness, as charge carrier contributors, were found as critical features for band gap and electrical resistivity, respectively. Effects on microstructural features should be considered as well as prerequisite in film design because of complex crystal growth mechanism.

Development of highly sensitive Al, Ga, and In-doped ZnO films by the drop casting method for NH3 gas sensing

This article proposes 2 wt% of aluminum, indium, and gallium-doped ZnO thin film samples for ammonia gas sensors.

Enhancing the electrochemical performance of graphene supercapacitors by coating their electrodes with a slurry-paste of ZnO:Al, ZnO:Ga and ZnO:In

This investigation reports the morphological and structural properties of ZnO doped with the Al, In and Ga elements and its utilization as redox material to improve the capacitance and energy density of graphene supercapacitors (SCs). All the ZnO nanoparticles doped with these elements presented a plate-like morphology with irregular edges and had hexagonal wurtzite phase. Moreover, the values of band gap were obtained for the ZnO nanoparticles and they are reduced with the order of: ZnO:Ga (3.2 eV)>ZnO:In (3.0 eV)>ZnO:Al (2.95 eV). The results of electrochemical characterization revealed that the graphene SCs made without ZnO presented a maximum capacitance and energy density of 97.2 F g−1 and 19.4 Wh kg−1, respectively. After the deposition of the Al, In or Ga-doped ZnO nanoparticles to the SC electrodes, the capacitance and energy density are enhanced by 22–193%. The maximum values of capacitance and energy density of 284.6 F g−1 and 56.9 Wh kg−1 were observed for the SC made with ZnO:Al. Moreover, the analysis by Raman and photoluminescence demonstrated the presence of Zinc interstitials, oxygen vacancy and oxygen interstitials defects, which served as redox centers for the charge storage in the solid state SCs. In general, this research confirmed that adding doped ZnO into the SCs is a good strategy to increment their performance, which is of interest for energy storage applications.

Green synthesis, characterization, antibacterial activity of metal nanoparticles and composite oxides using leaves extract of Ocimum basilicum L.

Nanoparticles plays a key role in the development of novel antibacterial substances against various pathogenic microorganisms. These nanoparticles due to their smaller size could be very effective as they can improve the antibacterial activity through lysis of bacterial cell wall. In the present research work, ZnO, MgO, NiO, AlO nanoparticles, and MgNiO, and AlZnO composite oxides were synthesized by green method from Ocimum basilicum leaves extract. The nanoparticles formed were evaluated using FTIR, XRD, EDX, and SEM to confirm the formation of NPs and to determine the morphology, elemental composition, shape and size, composition, and nature of bonds present in the NPs. Further, the NPs were tested for their antibacterial activity. In particular, ZnO NPs showed a good inhibitory effect against Pseudomonas aeruginosa with 20 mm zone of inhibition. Hence, the process reported herein could be optimized for large-scale preparation of NPs. RESEARCH HIGHLIGHTS: Green synthesis of ZnO, MgO, NiO, AlO nanoparticles, and MgNiO, and AlZnO composite oxides using Ocimum basilicum leaves extract NPs were characterized by various established characterization techniques like FTIR, XRD, EDX, and SEM. NPs showed antibacterial activity which was investigated by agar well diffusion method against Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The method proved to be very simple, cost-efficient, and convenient.

Spatial profile of Al-ZnO thin film on polycarbonate deposited by ring-shaped magnetized rf plasma sputtering with two facing cylindrical Al2O3 – ZnO targets

Radial profiles of the ion saturation current are measured in a ring-shaped magnetized radio-frequency plasma sputtering process with two facing cylindrical ZnO targets including Al2O3 (2% wt.). The profile has a non-uniform shape with a peak whose position corresponds to the target near the electrode due to the effect of the magnetic field distribution. It becomes uniform at large distances between the substrate and a target (d st ≥ 50 mm). The radial profile of the resistivity of the Al-ZnO (AZO) films deposited on a polycarbonate plate at Ar gas pressure of 0.27 Pa is uniform at about 10−3 Ω · cm for d st ≥ 50 mm. The films deposited at various positions and room-substrate-temperature also show a good crystallinity based on an X-ray diffraction peak of about 33.95–34.44°. The grains exhibit a preferential orientation along the [002] axis with its size ranging from 18.15 to 28.17 nm. A higher transmittance of 95.6% in the visible region is also obtained.

La1-xSrxMO3 (M = Co, Mn, Cr) interconnects in a 4-leg all-oxide thermoelectric generator at high temperatures

We herein report tests at high temperatures of a 4-leg oxide thermoelectric generator consisting of two pairs of p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO), assembled with various conducting perovskite oxides as interconnects. Using a custom-built testing system, we evaluated performance and stability at a hot side (furnace) temperature of up to 1000 °C under temperature differences up to ΔT = 600 °C in air. With a La0.6Sr0.4CoO3 (LSC) interconnect, a maximum power output of 18 mW was achieved with TH = 940 and TC = 340 °C (ΔT = 600 °C). Power maxima with La0.8Sr0.2MnO3 (LSM) and La0.8Sr0.2CrO3 (LSCr) as interconnects were lower, 6 mW and 2 mW, respectively, under similar conditions, attributed to their lower thermal and electrical conductivities. This demonstrates the requirements and potential of oxide interconnects for stable use of all-oxide thermoelectric generators at high temperatures in ambient air.

A ReaxFF potential for Al–ZnO systems

A reactive field force potential has been created in order to model the structural effects of low percentage dopant aluminium in a zinc oxide (ZnO) system. The potential’s parameters were fitted to configurations computed with density functional theory: binding energies were considered for surface structures and for Al in ZnO bulk crystals. Energies for Zn–Al alloys were also considered. Forces were fit to zero for all equilibrium structures and were also fitted for some non-equilibrium structures. As a first application of the model, the energetic deposition (0.1–40 eV) of an aluminium atom onto the polar surface of a ZnO is considered. For low energies the Al atom attaches to two preferred sites on the surface but as the energy increases above ≈15 eV subplantation is preferred at near normal incidence, with high diffusion barriers between stable sites. At these energies, reflection of the Al atom occurs at incident angles above .

Preparation and Characterization of Cu and Al Doped ZnO Thin Films for Solar Cell Applications

The Al- and Cu-doped ZnO nanostructured films in this study were deposited using a sputtering technique. Investigations based on X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Hall effect measurements, and optical transmission spectroscopy was performed to analyze the structural, electrical, and optical characteristics of the prepared Al–ZnO and Cu–ZnO nanostructured films. The analyses show that doping results in enhanced conductivity as well as improved mobility in Al–ZnO and Cu–ZnO films in comparison to pure ZnO films. The Al- and Cu-doped ZnO films exhibited low resistivity (2.9 × 10−4 Ω cm for Al–ZnO and 1.7 × 10−4 Ω cm for Cu–ZnO) along with an average transmittance of around 80% in the visible spectrum. Moreover, the optical bandgaps of undoped ZnO, Al–ZnO, and Cu–ZnO nanostructures were observed as 3.3, 3.28, and 3.24 eV, respectively. Finally, solar cells were assembled by employing ZnO nanostructured thin films as photoelectrodes, resulting in efficiencies of 0.492% and 0.559% for Al–ZnO- and Cu–ZnO-based solar cells, respectively.

Localized surface plasmon and transferred electron enhanced UV emission of ZnO by periodical aluminum nanoparticle arrays

Periodical Al nanoparticle (NP) arrays were applied to enhance the ultraviolet (UV) light emission of ZnO by localized surface plasmon resonance (LSPR) effect and electron transfer mechanism. By applying corresponding anodic aluminum oxide (AAO) templates, periodical Al NP arrays with different diameters (D) and spaces (S) were manufactured by magnetron sputtering. Theoretical simulation by FDTD-solution indicates that local electric field around Al NPs is significantly enhanced, and the surface plasmon resonance wavelength is determined by D and S. Al NP arrays with D of 70 nm and S of 125 nm enhanced near band-edge emission of ZnO by 2.4 times. By adding Al NP arrays, the photonic lifetime of ZnO decreased by 0.09 ns according to time-resolved photoluminescence spectra, indicating that the enhancement in UV luminescence intensity of ZnO is ascribed to the coupling between surface plasmons of Al NPs and ZnO excitons. Deep-level emission spectra analysis indicates that there lies another mechanism of electron transfer from the Al NPs to surface plasmon resonance (SPR) level and then further to ZnO conduction band.

Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators

Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction.