Aluminum-doped Zinc Oxide Research Articles

Aluminum-doped ZnO nano-laminar structures by pulsed laser ablation for gas sensing application

Aluminum-doped ZnO nano-laminar structures by pulsed laser ablation for gas sensing application

High optoelectronic quality of AZO films grown by RF-magnetron sputtering for organic electronics applications

Aluminum-doped zinc oxide thin films, known by the acronym AZO, were grown by radio-frequency magnetron sputtering method (rf-magnetron sputtering) onto glass substrate at room temperature and without posterior heat treatment. The impact on the structural, electrical, and optical properties of the AZO films was studied as a function of the following deposition parameters: working pressure, rf-power and thickness. Our films showed low electrical resistivity and high transmittance in the visible region comparable to commercial indium tin oxide (ITO) films. We obtained an optimized AZO film with an electrical resistivity of 4.90 × 10−4 Ωcm and presented optical transmittance strikingly high for such a good conductor, with about 98% at 580 nm and an average optical transmittance of about 92% in the visible region. We also built and characterized an organic light-emitting diode (OLED) using the optimized AZO film as a transparent electrode. The AZO-based OLED showed characteristics comparable to a reference ITO-based device, indicating that AZO films have optoelectronic properties good enough to be used in organic electronics. In addition, the results suggest that they are suitable to be employed as transparent conductors in flexible polymeric substrates since their synthesis was performed without intentional heating.

Optical, structural, electrical and photocatalytic properties of aluminum doped zinc oxide nanostructures

The Al-doped ZnO (Zn1-xAlxO, x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanostructures were synthesized by the chemical vapor deposition technique. Analysis by X-ray diffraction reveals that both undoped and Al-doped ZnO nanostructures are crystallized in a single-phase wurtzite structure with a preferred orientation along the (101) plane. The addition of Al was studied to see how it influenced bond length, crystallite size, unit cell volume, lattice strain, and dislocation density. Field-emission scanning electron microscope imaging showed a significant variation in the morphology with increasing the Al doping level. Absorption spectra in the UV–Visible range revealed that introducing Al3+ ions into the ZnO lattice causes a blue shift in the optical band gap, which was explained according to Burstein-Moss effect and variation of the electronic structure. The direct electrical conductivity measurement showed a transformation between two conduction mechanisms upon variation of the temperature. Transition of the charge carriers from shallow and deep donor levels dominated in the low and high temperature ranges, respectively. The photodegradation rate constants and degradation efficiency were determined as well as the photocatalytic mechanism was described. Upon reaching the x = 0.08 Al doping level, the photocatalytic efficiency of the examined samples increased by 1.7-fold. The obtained results demonstrate that Al doping can tune the electrical, optical, and photocatalytic properties of ZnO nanostructures that make them applicable for many optoelectronic applications.

Two-dimensional silver film for all-inorganic transparent photovoltaics

A transparent conductor with aluminum-doped zinc oxide (AZO)/Ag/Cu structure was developed and applied for extracting power from transparent photovoltaics. The Cu layer serves as seed layer for the two-dimensional growth of an Ag film. The AZO layer is used to enhance the optoelectrical properties of Cu/Ag. The AZO/Ag/Cu film exhibits a high visible transmittance of 83.1% and a sheet resistance of 18 Ω/□. Importantly, the proposed Cu/Ag/AZO transparent conductor enables the development of transparent and flexible NiO/ZnO-based photovoltaics with a power conversion efficiency of 1.14%. These results shows that the present system may be a promising platform for cost-effective and high-performance flexible optoelectronics.

Simultaneous removal of sulfamethoxazole, 17β-estradiol, and carbamazepine from hospital wastewater using a combination of a continuous constructed wetland-based system followed by photocatalytic reactor

Pharmaceutically active compounds (PhACs), such as sulfamethoxazole, 17β-estradiol, and carbamazepine, are ubiquitous in hospital effluent and are resistant to conventional treatment methods. Advanced oxidation techniques like photocatalysis can degrade these compounds, but their performance in continuous mode and real wastewater matrix is inadequate. Hence, this study uses an iron-modified aluminum-doped ZnO (Al-ZnO/Fe) photocatalyst to degrade sulfamethoxazole, carbamazepine, and 17β-estradiol simultaneously. Batch studies indicated that at pH 8 and 0.5 g/L of photocatalyst, removal efficiencies of sulfamethoxazole, 17β-estradiol, and carbamazepine were 98.93 ± 0.27%, 98.28 ± 0.35%, and 98.31 ± 0.57%, respectively. The toxicity of the intermediate products formed and potential application of the spent photocatalyst was also studied. However, removal of PhACs was decreased when the conditions were replicated in the continuous mode. Moreover, their removal in tap water and real hospital wastewater was further reduced. The presence of inhibiting agents in real wastewater attributed to the decrease in PhACs removal. In this context, a continuous baffled horizontal flow subsurface constructed wetland-based system followed by the photocatalytic reactor was used to treat hospital wastewater spiked with sulfamethoxazole, 17β-estradiol, and carbamazepine, and the removal efficiencies were found to be 97.16 ± 1.85%, 98.09 ± 0.92%, and 96.02 ± 2.27%, respectively.

Se-Vacancy Healing with Substitutional Oxygen in WSe2 for High-Mobility p-Type Field-Effect Transistors.

Transition-metal dichalcogenides possess high carrier mobility and can be scaled to sub-nanometer dimensions, making them viable alternative to Si electronics. WSe2 is capable of hole and electron carrier transport, making it a key component in CMOS logic circuits. However, since the p-type electrical performance of the WSe2-field effect transistor (FET) is still limited, various approaches are being investigated to circumvent this issue. Here, we formed a heterostructural multilayer WSe2 channel and solution-processed aluminum-doped zinc oxide (AZO) for compositional modification of WSe2 to obtain a device with excellent electrical properties. Supplying oxygen anions from AZO to the WSe2 channel eliminated subgap states through Se-deficiency healing, resulting in improved transport capacity. Se vacancies are known to cause mobility degradation due to scattering, which is mitigated through ionic compensation. Consequently, the hole mobility can reach high values, with a maximum of approximately 100 cm2/V s. Further, the transport behavior of the oxygen-doped WSe2-FET is systematically analyzed using density functional theory simulations and photoexcited charge collection spectroscopy measurements.

Novel DAZO Film with a Negative Temperature Coefficient Effect and Its Application Prospects for the Thermal Runaway Warning System in Batteries

A novel dopamine- and aluminum-doped zinc oxide (DAZO) sensing film was prepared by blending DAZO nanoparticles with silicone latex; this film has promising applications for the thermal runaway warning system of new energy batteries. The DAZO nanoparticles were generated by the coprecipitation–calcination method through the structure-orienting modification of eco-friendly polydopamine biomaterials, followed by the doping of aluminum and nitrogen into the zinc oxide lattice. Dopamine was used as a nitrogen source; it easily self-polymerizes to form polydopamine, which is then pyrolyzed and doped into the zinc oxide lattice. The negative temperature coefficient (NTC) effects of the DAZO film and the aluminum-doped zinc oxide (AZO) film below 150 °C were tested and compared. The results showed that the DAZO film had a more pronounced NTC effect than the AZO film because of the doped nitrogen element. DAZO films exhibited good recyclability and thermal stability during the high-low temperature NTC cycle test. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry/mass spectrometry (TG–MS), and energy dispersive X-ray spectroscopy were performed to characterize the fabrication of the synthesis mechanism of the DAZO nanoparticles. The NTC effects of DAZO films with varying aluminum doping amounts, varying dopamine doping amounts, and different pH values were investigated. Nitrogen doping in the conventional AZO nanoparticles enhanced the sensitivity and low-temperature NTC effect; this is because of the increase in the DAZO grain size due to doping and the structure–orientation of polydopamine, which further leads to the increase in the height of the grain boundary potential barrier. On the basis of the test results, an alarm response device at different temperatures was initially established, and its alarm response at different temperatures was simulated and tested, which showed the possibility of the application of the DAZO film to the runaway warning system for the new energy batteries.

Peak amplitude difference sensitivity (PADS): An interrogation technique for PCF-SPR sensors using symmetrical arrays of plasmonic layers

In this research paper, plasmonic materials are used in somearrays consisting of goldand aluminum-doped zinc oxide (AZO) to make a unique photonic crystal fiber sensor with multipleloss peaks. Using plasmonic layer arrays, a unique dispersion relation with severalpeaks has been introduced. Compared to a sensor with a single peak, the proposed sensor has multiple peaks that can be applicable for different wavelength range to detect the refractive index efficiently. A new interrogation technique named Peak Amplitude Difference Sensitivity (PADS) is proposed in this manuscript while in this sensor, the maximum PADS of 396.175 RIU−1 and maximum wavelength sensitivity (WS) of 85,300 nm/RIU is achieved. Furthermore, thesensor has a high wavelengthresolution of 1.17×10-6 RIU. With an ultra-high linearity of R2=0.99978, this sensor obtained a high figure of merit (FOM) of 370.8 RIU−1, indicating precise detection accuracy. The proposed design canlead to major improvements in the ultra-high precision in detecting the biological organic molecules and can be used in extensive applications.

Numerical modeling and analysis of AZO/Cu2O transparent solar cell with a TiO2 buffer layer

In the present work, titanium dioxide (TiO2) is sandwiched as a buffer layer between n-type aluminum-doped zinc oxide (AZO) and p-type cuprous oxide (Cu2O), increasing the efficiency of metal oxide-based solar cells. The effects of the device parameters such as thicknesses, carrier concentrations, and defect densities were investigated by numerical simulation to obtain optimal performance of Cu2O-based solar cells. Our findings reveal that by the incorporation of TiO2 thin film, the efficiency of the solar cell increases remarkably from 2.54 to 5.02 %. The optimal thicknesses of the Cu2O and TiO2 layers are in the range of 10 μm and 0.1 μm, respectively. We obtained optimal photo-electric conversion efficiency of 10.17 % and open-circuit voltage of 1.35 V while achieving 8.90 mA/cm2 short-circuit current density and 84.12 % fill factor, using structure parameters of 0.2 μm AZO, 0.1 μm TiO2 and 10 μm Cu2O with optimal acceptor-type dopant density in Cu2O of 1E17 cm−3 and donor-type dopant density in TiO2 of 1E18 cm−3.

Photothermoelectric AZO/SiO2/NiO Device

AbstractTransparent‐conductive‐oxide (TCO) materials and transparent devices combining photovoltage and thermoelectric effects are still scarce. Hence, a new transparent‐conductive‐oxide/insulating/transparent‐semiconductor‐oxide (TCO‐I‐TSO) structure combining such effects is developed. It is made of aluminum‐doped zinc oxide (AZO)/SiO2/NiO thin films sequentially deposited on glass substrates. AZO exhibits thermo and photovoltage in response to gradient temperature and absorption of UV photons, while NIR photons absorption in the NiO layer. Photovoltage appears in the plane between the AZO and NiO layer when the whole sample is irradiated with near infrared light, and it also depends on the thickness of the SiO2 layer. This photovoltage is continuously monitored on samples placed in a glass window facing south. Throughout the day, the photovoltage varies from 0 to 300 µV proportionally to the light intensity.

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

Development of AZO TCOs with ALD for HEMT and HJSC Solar Cell Applications

Transparent Conductive Oxide (TCO) films are widely used in optoelectronic devices, such as solar cells, LEDs, and Lasers. Utilization of these contacts directly affects the device efficiencies. Purpose of this study is to produce and optimize properties of Aluminum doped Zinc Oxide (AZO) using a vapor phase technique, Atomic Layer Deposition (ALD) for (n+) a-Si:H surface of silicon Heterojunction Solar Cells (HJSCs) and High Electron Mobility Transistor (HEMT) applications. This study is focused on the effect of the deposition temperature and aluminum atomic concentration on structural, electrical and optical properties of ALD grown AZO ohmic contact films. The results show that as-deposited films have 80-90% transmittance in the visible spectra, low resistance (2.04x10-3 ohm.cm) and mobility value of 5.25 cm2/V.s.

AZO work function enhanced by oxygen plasma immersion ion implantation

The surface of aluminum-doped ZnO (AZO) films was modified using the oxygen plasma immersion ion implantation method, which is also called O-PIII. The modified AZO films were analyzed by an X-ray photoelectron spectroscopy system (XPS), X-ray diffraction (XRD), a UV–visible spectrophotometer, atomic force microscopy (AFM), and a Kelvin probe instrument (KP). The results showed that O-PIII modification can further enhance the work function (WF) of AZO based on oxygen plasma (O-ICP) treatment. The optical characteristics of AZO thin films are nearly entirely preserved, and the surface morphology is enhanced. The variation in WF was strongly linked to the surface stoichiometry. The reduction of oxygen vacancies should be attributed to the high WF. The WF of the modified AZO films decreased rapidly with exposure time in the air promptly following O-ICP and O-PIII modification. Nonetheless, the O-PIII treatment had a longer-lasting effect.

Field enhancement of epsilon-near-zero modes in realistic ultrathin absorbing films

Abstract Using electrodynamical description of the average power absorbed by a conducting film, we present an expression for the electric-field intensity enhancement (FIE) due to epsilon-near-zero (ENZ) polariton modes. We show that FIE reaches a limit in ultrathin ENZ films inverse of second power of ENZ losses. This is illustrated in an exemplary series of aluminum-doped zinc oxide nanolayers grown by atomic layer deposition. Only in a case of unrealistic lossless ENZ films, FIE follows the inverse second power of film thickness predicted by S. Campione, et al. [Phys. Rev. B, vol. 91, no. 12, art. 121408, 2015]. We also predict that FIE could reach values of 100,000 in ultrathin polar semiconductor films. This work is important for establishing the limits of plasmonic field enhancement and the development of near zero refractive index photonics, nonlinear optics, thermal, and quantum optics in the ENZ regime.

Gallium-doped zinc oxide: nonlinear reflection and transmission measurements and modeling in the ENZ region

Strong nonlinear materials have been sought after for decades for applications in telecommunications, sensing, and quantum optics. Gallium-doped zinc oxide is a II–VI transparent conducting oxide that shows promising nonlinearities similar to indium tin oxide and aluminum-doped zinc oxide for the telecommunications band. Here we explore its nonlinearities in the epsilon near zero (ENZ) region and show n 2,eff values on the order of 4.5 × 10−3 cm2GW−1 for IR pumping on 200–300 nm thin films. Measuring nonlinear changes in transmission and reflection with a white light source probe in the near-IR while exciting in the near-IR provides data in both time and wavelength. Three films varying in thickness, optical loss, and ENZ crossover wavelength are numerically modeled and compared to experimental data showing agreement for both dispersion and temporal relaxation. In addition, we discuss optimal excitation and probing wavelengths occur around ENZ for thick films but are red-shifted for thin films where our model provides an additional degree of freedom to explore. Obtaining accurate nonlinear measurements is a difficult and time-consuming task where our method in this paper provides experimental and modeled data to the community for an ENZ material of interest.

> 85% indium reduction for high-efficiency silicon heterojunction solar cells with aluminum-doped zinc oxide contacts

> 85% indium reduction for high-efficiency silicon heterojunction solar cells with aluminum-doped zinc oxide contacts

Recent Progress in Solution Processed Aluminum and co-Doped ZnO for Transparent Conductive Oxide Applications.

With the continuous growth in the optoelectronic industry, the demand for novel and highly efficient materials is also growing. Specifically, the demand for the key component of several optoelectronic devices, i.e., transparent conducting oxides (TCOs), is receiving significant attention. The major reason behind this is the dependence of the current technology on only one material-indium tin oxide (ITO). Even though ITO still remains a highly efficient material, its high cost and the worldwide scarcity of indium creates an urgency for finding an alternative. In this regard, doped zinc oxide (ZnO), in particular, solution-processed aluminum doped ZnO (AZO), is emerging as a leading candidate to replace ITO due to its high abundant and exceptional physical/chemical properties. In this mini review, recent progress in the development of solution-processed AZO is presented. Beside the systematic review of the literature, the solution processable approaches used to synthesize AZO and the effect of aluminum doping content on the functional properties of AZO are also discussed. Moreover, the co-doping strategy (doping of aluminum with other elements) used to further improve the properties of AZO is also discussed and reviewed in this article.

Sensitivity of Al-Doped Zinc-Oxide Extended Gate Field Effect Transistors to Low-Dose X-ray Radiation

Herein, we investigated the applicability of thick film and bulk disk forms of aluminum-doped zinc oxide (AZO) for low-dose X-ray radiation dosimetry using the extended gate field effect transistor (EGFET) configuration. The samples were fabricated using the chemical bath deposition (CBD) technique. A thick film of AZO was deposited on a glass substrate, while the bulk disk form was prepared by pressing the collected powders. The prepared samples were characterized via X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) to determine the crystallinity and surface morphology. The analyses show that the samples are crystalline and comprise nanosheets of varying sizes. The EGFET devices were exposed to different X-ray radiation doses, then characterized by measuring the I-V characteristics pre- and post-irradiation. The measurements revealed an increase in the values of drain-source currents with radiation doses. To study the detection efficiency of the device, various bias voltages were also tested for the linear and saturation regimes. Performance parameters of the devices, such as sensitivity to X-radiation exposure and different gate bias voltage, were found to depend highly on the device geometry. The bulk disk type appears to be more radiation-sensitive than the AZO thick film. Furthermore, boosting the bias voltage increased the sensitivity of both devices.

Integrated atmospheric microplasma with ultrasonic spray pyrolysis deposition of aluminum-doped zinc oxide

Aluminum-doped zinc oxide (AZO) has electrical conductivity and visible light transmittance similar to those of indium tin oxide that is used in modern display devices at a lower price. Thus, many studies regarded it as an alternative material for transparent conductive oxide coating. This study has integrated atmospheric microplasma with an ultrasonic spray pyrolysis deposition system to prepare economically and rapidly AZO using zinc chloride and aluminum chloride as precursors. The low electrical resistivity of the coating prepared in this system is proposed to be due to free radicals and reactive oxygen. They are generated by the atmospheric plasma that is adsorbed to the layer, thereby decreasing oxygen vacancy and free carrier concentration. Vacuum annealing heat treatment was used to improve the properties of the coating; the resistivity of argon-annealed AZO was [Formula: see text]–cm with 80% transmittance, thus meeting the transparent conducting oxide requirements.

The Effect of Post Deposition Treatment on Properties of ALD Al-Doped ZnO Films

In this paper, aluminum-doped zinc oxide (ZnO:Al or AZO) thin films are grown using atomic layer deposition (ALD) and the influence of postdeposition UV-ozone and thermal annealing treatments on the films' properties are investigated. X-ray diffraction (XRD) revealed a polycrystalline wurtzite structure with a preferable (100) orientation. The crystal size increase after the thermal annealing is observed while UV-ozone exposure led to no significant change in crystallinity. The results of the X-ray photoelectron spectroscopy (XPS) analyses show that a higher amount of oxygen vacancies exists in the ZnO:Al after UV-ozone treatment, and that the ZnO:Al, after annealing, has a lower amount of oxygen vacancies. Important and practical applications of ZnO:Al (such as transparent conductive oxide layer) were found, and its electrical and optical properties demonstrate high tunability after postdeposition treatment, particularly after UV-Ozone exposure, offers a noninvasive and easy way to lower the sheet resistance values. At the same time, UV-Ozone treatment did not cause any significant changes to the polycrystalline structure, surface morphology, or optical properties of the AZO films.