Metal Doped Zinc Oxide Research Articles

Optimizing excited state adsorption and carrier dynamics of metal doped zinc oxide by p-d orbital modulation for efficient reverse saturation absorption

Doping metals can regulate the excited state adsorption and carrier transport efficiency of ZnO through p-d orbital coupling thereby improving its nonlinear performance. Herein, the thin film coatings consisting of ZnO, and M-ZnO (M=Al, Sn, Mg) were synthesized using the magnetron sputtering technique. ZnO exhibited the granular/stick structure, while the metal dopant atoms (M) were incorporated into the ZnO lattice, resulting in a homogeneous distribution. Photoluminescence spectroscopy reveals the quenched defect emission intensity, indicating a decrease in the rate of photo-induced electron-hole pair complexation. Mg exhibits an optimized effect to promote the saturation absorption of ZnO, resulting in the enhancement of the nonlinear absorption (NLA) coefficients for M-ZnO films. Al-ZnO and Sn-ZnO films exhibit reverse saturation absorption. Theoretical simulation shows that the additions of transition metal atoms favor the electron transfer through p-d orbital modulation of ZnO. The p-d hybridization causes the metal-d orbitals to cross the Fermi level and form an electron transport channel, thereby enhancing the excited state absorption, and effectively controlling the NLA process and mechanism. The excited state absorption of the M-ZnO films significantly rises. This research demonstrates that the optimization of excited state absorption through p-d orbital modulation is a highly effective strategy for the development of efficient and superior nonlinear optical absorbers.

Potential for multi-application advancements from doping zirconium (Zr) for improved optical, electrical, and resistive memory properties of zinc oxide (ZnO) thin films

Transition metal-doped Zinc oxide (ZnO) thin films with an optimal wide band gap and semiconducting nature find numerous applications in optoelectronic devices, gas sensors, spintronic devices, and electronics. In this study, Zirconium (Zr) doped ZnO thin films were deposited on ITO (Indium Tin oxide) coated glass substrate using RF-magnetron sputtering. Optical and electrical properties were examined for their potential use in resistive random-access memory (RRAM) applications. X-ray Diffraction (XRD), UV–vis spectroscopy, x-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM) and Scanning electron microscopy (SEM) were used to investigate structural, optical, and compositional properties and roughness respectively. The results demonstrate that the films possess crystalline properties. Additionally, an augmentation in Zr concentration correlates with an elevation in the optical band gap, ascending from 3.226 eV to 3.26 eV, accompanied by an increase in Urbach energy from 0.0826 eV to 0.1234 eV. The film with the highest Zr content among all the films demonstrated the best electrical performance for resistive memory applications. Incorporating Zr as a dopant shows enhancement in the electrical performance and such ZnO films with optimum concertation of Zr can potentially be used in RRAM. ZnO being a versatile host material, its doping with Zr may extend its applications in catalysis, gas sensing, energy storage, and biomedical engineering. ZnO thin films employ zirconium (Zr) as a dopant, which is a novel way to improve the material’s characteristics. Although ZnO has been thoroughly researched, adding Zr presents a novel technique to enhance optical, electrical, and resistive memory characteristics all at once that has not been fully investigated.

Tuning the structural, optical and magnetic properties of transition metal doped zinc oxide nanoparticles

Tuning the structural, optical and magnetic properties of transition metal doped zinc oxide nanoparticles

Metal-doped functional zinc oxide nanosheets as flexible piezoelectric generator for self-powered mechanical sensing

The development of self-powered active mechanical sensors, which enable tactile sensing capabilities for soft robotics, has been substantially accelerated by the invention and rapid advancement of piezoelectric nanogenerators that harness mechanical energy from the environment as electricity. However, fabrication methods and sensory output expansion of nanogenerators are still challenging to meet the stability and durability requirements during prolonged use. In this work, metal-doped zinc oxide nanomaterial-polymer composites are prepared, characterized, and fully embedded in the flexible substrates to fabricate piezoelectric sensors with enhanced output performance and sensing capabilities. The flexible device can generate an open-circuit voltage up to 13.6 V when the applied force is 8 N at 3 Hz. In addition, these lead-free composite devices exhibit remarkable elbow motion detection sensitivity, providing a tremendous potential for precise human body motion sensing. Further, based on the sensors, a biomimetic soft robotic fin with mechanosensation has been developed, which can measure both the amplitude and frequency of the flapping of the fin ray. These findings not only shed new light on the development of functionl piezoelectric nanogenerators, but also lay the framework for advanced ambient sensing capacities of underwater organisms or robots.

Significant advancements in passivating crystalline silicon surfaces achieved through the implementation of metal-doped zinc oxide layers

Significant advancements in passivating crystalline silicon surfaces achieved through the implementation of metal-doped zinc oxide layers

Controlling surface morphology of Ag-doped ZnO as a buffer layer by dispersion engineering in planar perovskite solar cells

In recent years, the power conversion efficiency (PCE (%)) of perovskite solar cells (PSCs) has improved to over 26%. To enhance the photovoltaic properties of PSCs, several materials for the electron transport layer (ETL) have been investigated. Zinc oxide (ZnO) is a significant ETL due to its high electron mobility and optical transparency in PSCs. As a result of various deposition methods, ZnO ETL can be processed at low temperatures. On the other hand, based on several studies, metal-doped ZnO can facilitate electron transfer, thereby improving the performance of un-doped ZnO ETL-based PSCs. Here, to improve the PCE (%) and long-term stability of un-doped ZnO ETL-PSCs, silver (Ag)-doped ZnO 1wt% as a buffer layer is examined. In this paper, with the addition of an organic solvent (ethanol) to the dispersion of Ag-doped ZnO 1 wt% nanoparticles (NPs) in deionized (DI) water, the morphology of the buffer layer (Ag-doped ZnO 1 wt%) can be controlled. This approach focuses on reducing the wettability of the ZnO/Ag-doped ZnO 1 wt% bilayer ETLs and enhancing the stability of un-doped ZnO ETL-PSCs. According to the results, the ZnO/H2O-ethanol mixtures-Ag-doped ZnO 1 wt% bilayer ETL leads to the formation of high-quality perovskite with low defects, reducing the recombination rate, and long-term stability of un-doped ZnO ETL-PSCs in ambient conditions.

Photodegradation of methylene blue dye using graphene oxide incorporated, post-transition metal doped zinc oxide thin films by spray pyrolysis

Photocatalytic activity of graphene oxide incorporated pure and metal doped zinc oxide thin films were studied against methylene blue dye under simulated solar irradiation. Thin films were deposited on a glass substrate using an automated spray pyrolysis technique at a temperature of 425 °C. Aluminium, gallium, and indium were the post-transition metals used for doping. Graphene oxide content in the precursor solution was fixed at 0.00375 g/l. The formation of the wurtzite structure of zinc oxide has been confirmed using structural analysis. The average crystallite size of all the thin film samples was found to be in the range of 45–55 nm. The morphology and elemental composition of the films were studied using scanning electron microscopy and energy-dispersive x-ray spectroscopy. The energy band gap of the material was determined from UV–vis-NIR spectroscopic measurements using Tauc’s plot and it is in the range of 3.25–3.28 eV. Photoluminescence spectra of the as-deposited films were recorded. Intensity of the near band emission at 395 nm was found to decrease upon metal doping, indicating a better photocatalytic property. All the films were used for heterogeneous photocatalysis and the indium doped zinc oxide thin film incorporated with graphene oxide was found to be a better catalyst with an efficiency of 94.9% for degrading methylene blue dye in 180 min.

Anti-proliferative activity of biosynthesized zinc oxide nanoparticles against breast cancer MCF-7 cells

Nanomaterials are a subject of immense interest within cancer research, primarily due to their promising role as potent anticancer agents, particularly in the context of targeted drug delivery. The present research work aims at exploring the antiproliferative potential of both undoped and metal doped Zinc oxide nanoparticles (ZnO NPs) synthesized using bio-assisted methods against MCF-7 breast cancer cell lines. Undoped and Cu and Ag metal doped ZnO NPs were synthesized using various bio-assisted methods and appropriately characterized using PXRD, FTIR, UV–vis spectroscopy, DLS and SEM. The NPs were subsequently diluted using ultrapure water to final concentrations ranging from 10 to 2.5 μg/ml. The antiproliferative efficiency of these NPs was assayed using WST-8 assay by measuring cell proliferation following exposure to various concentrations of these NPs over 24-h duration. The results of this study reveal that the undoped ZnO NPs synthesized using E officinalis fruit and P granatum peel aqueous extracts exhibit significant inhibitory impacts on MCF-7 cancer cells, particularly at higher concentrations. There was nearly a 45 % MCF-7 breast cancer cell line growth inhibition by both these NPs at the highest tested concentration of 10 μg/ml. Additionally, metal doped ZnO NPs demonstrated heightened inhibitory ability in comparison to undoped ones. Among Cu and Ag doped ZnO NPs, 3 M Ag doped ZnO NPs caused nearly 56 % MCF-7 breast cancer cell line growth inhibition at the highest tested concentration of 10 μg/ml.The authors noted that the adoption of novel bio-assisted synthesis methodologies showcases considerable potential in tailoring ZnO NPs properties to suit biomedical applications. Various forms of ZnO NPs used in the current study, underscores their potential as valuable tools in cancer treatment towards MCF-7 breast cancer cell lines, with a specific emphasis on the positive synergies realized when combining phytocompounds with ZnO NPs to enhance their antiproliferative effects.

Enhanced photocatalytic activity of graphene oxide incorporated ZnO nanorods doped with post-transition metals

Photocatalytic activity of graphene oxide incorporated pure and selected post-transition metal doped zinc oxide nanorods were investigated for the degradation of methylene blue dye. Thin film seed layers were deposited on microscopic glass slides using an automated spray pyrolysis technique at a substrate temperature of 425 °C. Aluminium, gallium, and indium were the metals used for doping. Graphene oxide content in the precursor solution was fixed at 0.00375 g/L. Nanorods of the aforesaid transparent conducting oxide materials were grown by aqueous chemical growth technique, vertically over the respective as-deposited seed layers. Structural and optical properties of the nanorods were studied. Growth of the vertical nanorods was confirmed by scanning electron microscopy. All the nanorod samples were utilized as catalysts for repeated cycles of photocatalysis and the graphene oxide incorporated indium doped zinc oxide nanorod was found to be an efficient and stable photocatalyst by degrading 96.1 % of methylene blue dye in 180 min under simulated solar irradiation.

Investigation of Photoluminescence and Optoelectronics Properties of Transition Metal-Doped ZnO Thin Films.

Thin films of zinc oxide (ZnO) doped with transition metals have recently gained significant attention due to their potential applications in a wide range of optoelectronic devices. This study focuses on ZnO thin films doped with the transition metals Co, Fe, and Zr, exploring various aspects of their structural, morphological, optical, electrical, and photoluminescence properties. The thin films were produced using RF and DC co-sputtering techniques. The X-ray diffraction (XRD) analysis revealed that all the doped ZnO thin films exhibited a stable wurtzite crystal structure, showcasing a higher structural stability compared to the undoped ZnO, while the atomic force microscopy (AFM) imaging highlighted a distinctive granular arrangement. Energy-dispersive X-ray spectroscopy was employed to confirm the presence of transition metals in the thin films, and Fourier-transform infrared spectroscopy (FTIR) was utilized to investigate the presence of chemical bonding. The optical characterizations indicated that doping induced changes in the optical properties of the thin films. Specifically, the doped ZnO thin film's bandgap experienced a significant reduction, decreasing from 3.34 to 3.30 eV. The photoluminescence (PL) analysis revealed distinguishable emission peaks within the optical spectrum, attributed to electronic transitions occurring between different bands or between a band and an impurity. Furthermore, the introduction of these transition metals resulted in decreased resistivity and increased conductivity, indicating their positive influence on the electrical conductivity of the thin films. This suggests potential applications in solar cells and light-emitting devices.

Comparative studies of “3d” transition metals (Co, Mn, Ni) doped ZnO nanoparticles for visible light degradation of methylene blue

The development of efficient visible-light photocatalysts is highly desired for a clean and sustainable environment. Herein, we report the fabrication and functionalization of zinc oxide (ZnO) nanostructures for the degradation of organic pollutants, one of the key components of environmental pollution. Pure and “3d” transition metal ions doped ZnO (Zn1−xMxO, where M = Mn, Ni, Co with varying doping concentration x = 1 % and 7 %) were synthesized by co-precipitation method and their structural, electronic, morphological, and optical properties were investigated in detail. The powder X-ray diffraction (XRD) pattern of pure and Zn1−xMxO nanostructures confirmed the hexagonal wurtzite phase (p63mc) with an average crystallite size of around 22–27 nm. The energy dispersive x-ray (EDX) analysis confirmed the presence of metal dopants in ZnO. The morphology of synthesized nanostructures was found to be spherical. The band gap of ZnO was considerably narrowed from 3.15 to 1.8 eV through doping, indicating extension towards visible light absorption. Photoluminescence (PL) emission spectra of doped ZnO revealed a low recombination rate of electrons (e-) and holes (h+) and various possible defect states within the bandgap. Furthermore, electron spin resonance showed the presence of Mn2+ centers. Optimized metal-doped zinc oxide revealed higher photocatalytic activity, during degradation of methylene blue model dye under visible light.

Determination of bandgap of period 3, 4, and 5 transition metal dopants on zinc oxide using an artificial neural network based approach

Artificial intelligence (AI) and machine learning (ML) have rapidly emerged as valuable tools for chemical research, offering new ways to analyze and understand complex chemical systems. This research article investigates the use of adaptive neuro-fuzzy inference system (ANFIS) and multi-layer perceptron (MLP) models to predict the bandgap of transition metal doped zinc oxide (ZnO). The opto-electronic properties of transition metal doped ZnO complexes are of significant interest because of their applications is optoelectronic systems. The MLP and ANFIS models were trained using a dataset of experimentally measured bandgap values and the corresponding structural parameters of the doped ZnO systems. The performance of the models was evaluated using statistical metrics i.e., RMSE, R, and MAE. The results showed that both MLP and ANFIS models were capable of accurately predicting the bandgap of transition metal doped ZnO. However, the ANFIS model demonstrated superior performance with higher accuracy and better generalization ability. The study provides a useful approach for predicting the bandgap of transition metal doped ZnO using machine learning techniques and may contribute to the development of advanced optoelectronic devices.

Thermal and thermoelectric properties of metal-doped zinc oxide ceramics

The thermal, electrical and thermoelectric properties of ZnO–MexOy ceramics with 1 ≤ x, y ≤ 3, where Me = Al, Co, Fe, Ni, Ti, have been studied. The specimens have been synthesized using the ceramic sintering technology from two or more oxides in an open atmosphere with annealing temperature and time variation. The structural and phase data on the ceramics have shown that post-synthesis addition of MexOy doping powders to wurtzite-structured ZnO powder causes Znx (Mе)yO4 spinel-like second phase precipitation and a 4-fold growth of ceramics porosity. Room temperature heat conductivity studies have testified to predominant lattice contribution. A decrease in the heat conductivity upon doping proves to be caused by phonon scattering intensification due to the following factors: size factor upon zinc ion substitution in the ZnO lattice (wurtzite) by MexOy doping oxide metal ions; defect formation, i.e., point defects, grain boundaries (microstructure refinement); porosity growth (density decline); secondary phase particle nucleation (Znx (Mе)yO4 spinel-like ones). The above listed factors entailed by zinc ion substitution for metal ions (Co, Al, Ti, Ni, Fe) increase the figure-of-merit ZT by four orders of magnitude (due to a decrease in the electrical resistivity and heat conductivity coupled with a moderate thermo-emf decline). The decrease in the electrical resistivity originates from a more homogeneous distribution of doping metal ions in the wurtzite lattice upon longer annealing which increases the number of donor centers.

Energy distribution function of substrate incident negative ions in magnetron sputtering of metal-doped ZnO target measured by magnetized retarding field energy analyzer

The energy distribution function of the substrate incident negative ions during magnetron sputtering of a metal-doped zinc oxide target was measured using a home-made retarding field energy analyzer (RFEA) with a magnetic field region. The cross-field region in front of the RFEA injection aperture allows the bulk electrons in the plasma into the RFEA are dramatically suppressed, while the inflow of negative ions emitted from the oxide target is largely unaffected. Negative ions were found to be mainly emitted from the target erosion area and incident on the opposing substrate with ion energy equivalent to the target applied voltage. Compared to energy-resolved mass spectrometers, which require differential pumping and are large and not very portable, magnetized RFEA is inexpensive, compact and easy to sweep in space, although there is no mass separation.

Optical, Photocurrent, Electrical, Structural, and Morphological Properties of Magnetron Sputtered Pure and Iron-Doped Zinc Oxide Thin Films

Due to its excellent physical and chemical properties, transition metal-doped zinc oxide has potential applications in different fields. In this research paper, pure and iron-doped ZnO films were deposited by thermal oxidation of sputtered metallic zinc and iron. The effect of iron (Fe) doping on the optical, morphology, structural, electrical, and photocurrent properties of zinc oxide films was examined. The X-ray diffraction analysis shows a wurtzite structure with preferential orientation for all films, where the high texture coefficient values (above 3) corresponded to the (002) plane. Fe doping reduced the crystallite size from 12.3 to 8.7 nm and lattice constants c and a values from 5.19 to 5.155 Å and from 3.236 to 3.203 Å respectively. The different calculated structure parameters, confirm the incorporation of Fe (Fe3+) in the ZnO lattice. The surface morphology of thin films measured using atomic force microscopy revealed that the Fe doping could markedly decrease the grains size from 248 to 54 nm and the Root–Mean–Square roughness of films from 5.27 to 4.22 nm. For all films, the transmittance analysis shows a transmittance above 90% in the visible region and with an increase in the Fe concentration, the transmittance, and the absorption in the ultraviolet region were increased. The gap energy of ZnO strongly increased from 3.26 to 3.51 eV with doping. The effect of Fe doping on different optical parameters was discussed in detail. The photoluminescence analysis of pure and doped ZnO exhibits one ultraviolet emission (384 nm) and green emission. Compared to pure ZnO, the ultraviolet peak intensity decreased as Fe content increased. The electrical resistivity was decreased and the photocurrent properties of ZnO were enhanced by Fe doping. In this report, Fe-doped ZnO films exhibited remarkable properties. Therefore such films can be usefully used in different device applications.

Effect of Na and Al doping on ZnO nanoparticles for potential application in sunscreens.

This study investigated the environment-friendly production and characterization of zinc oxide nanoparticles (ZnO NPs) doped with sodium (Na) and aluminum (Al) metals to decrease the photocatalytic activity of ZnO for use in sunscreen. The metal-doped zinc oxide (ZnO) materials were prepared by the microwave method using extracts of Averrhoa carambola, also known as star fruit, as a reducing agent. The effects of metal-ion doping on the crystal structure, morphology, and optical characteristics of ZnO were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), and ultraviolet-visible (UV-Vis) spectroscopy. The sun protection factor (SPF) of the sunscreen formulations containing undoped ZnO, Na-doped ZnO (Na/ZnO), and Al-doped ZnO (Al/ZnO) NPs were found to be 10.10, 25.10, and 43.08, respectively. Therefore, Na/ZnO and Al/ZnO showed increased SPF. Additionally, the prepared nanomaterials and sunscreens were effective against Gram-positive and Gram-negative bacteria and showed antioxidant activities. The methylene blue (MB) degradation was used to evaluate the photocatalytic activities of the undoped ZnO, Na/ZnO, and Al/ZnO NPs, which were found to be 66%, 46%, and 38%, respectively. Therefore, due to the structural defects of ZnO NPs, their photocatalytic activity was decreased with Na- and Al- doping. Additionally, Al/ZnO is an ideal candidate as an ingredient in sunscreens.

Enhanced organic gas sensor based on Cerium- and Au-doped ZnO nanowires via low temperature one-pot synthesis

This paper presents gas sensors based on zinc oxide (ZnO), Ce-doped ZnO (CZO), and Au-doped CZO nanowires (NWs) for the detection of volatile organic compounds (VOCs). Three NW sensing materials were created via one-pot synthesis at low temperature (100 °C). CZO and Au-doped CZO NWs produced a large number of surface oxygen species, which enhanced the responsiveness of the sensors to all types of VOC. Note however that the ZnO NW sensors lacked sensitivity to isopropyl alcohol (IPA). We theorized that overcoming this issue would require doping ZnO NWs with noble metals or rare-earth elements. In experiments, we demonstrated that doping NWs with Au shifted the selectivity of a CZO NWs sensor from acetone to IPA. This study also proposes sensing mechanisms for three metal-doped ZnO NWs.

Sputter Deposited Mn‐doped ZnO Thin Film for Resistive Memory Applications

AbstractTransition metal doped Zinc oxide (ZnO) thin films with wide band gap semiconducting nature have diverse range of applications including, gas sensors, optical and optoelectronic devices, electronics and spintronics spintronic devices etc. In the present study, Manganese (Mn)‐doped ZnO thin films deposited on glass substrates using RF‐magnetron sputtering have been investigated for their optical and electrical behavior aiming at resistive random access memory applications. To study the influence of Mn doping and correlation between the structural and the physical properties of the films, the samples were characterized by X‐ray Diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X‐ray Spectroscopy (EDS), UV‐VIS spectrophotometry and X‐ray photoelectron spectroscopy (XPS). The films are found to be crystalline and a decrease in lattice parameter from 2.6049 Å to 2.5845 Å, an increase in optical band gap from 3.27 eV to 3.35 eV and a decrease in Urbach energy from 0.222 eV to 0.171 eV, is observed with increase in Mn‐concentration. The electrical performance of the film with highest Mn‐content is found to be more suitable for resistive memory applications. Tailoring the electrical behavior of the film by incorporating Mn as dopant is an important approach to find suitable material combination for novel memory devices.

Experimental and DFT study of structural and optical properties of Ni-doped ZnO nanofiber thin films for optoelectronic applications

As an important metal oxide semiconductor, transition metal-doped zinc oxide (ZnO) has attracted great interest for various applications in optoelectronic, spintronic photovoltaic and photodetectors due to its significant chemical and physical properties. In this research study, pure and nickel (Ni)-doped ZnO nanostructured films were synthesized via the sol-gel method using the spin coating technique on glass substrates. The structural results revealed that all samples exhibited a polycrystalline wurtzite structure and a (002) plane preferred orientation. The crystallite size was reduced by Ni doping. The morphology micrographs indicate that the surface of thin films shows nanofiber structures. An optical study revealed the high transparency of the films. The photoluminescence (PL) showed one ultraviolet (UV) emission at 387 nm and different defect emissions for all films. The absorption, band gap and PL emissions intensities were influenced by Ni doping. Ni-doped ZnO nanostructured thin films revealed high UV sensitivity and photoresponse. Therefore, these thin films are a promising material for a UV photodetector. The dielectric function, absorption coefficient and energy band gap were also calculated and discussed by density functional theory (DFT), using the Ultra Soft Pseudo Potential (US-PP) approach implemented in the CASTEP code.

Metal-doped zinc oxide nanostructures for nanogenerator applications: A review

Nanogenerators have been widely discussed and investigated in the literature due to their excellent development in various sectors and applications. There are two typical electricity generating mechanisms involved in nanogenerators, that include piezoelectric and triboelectric processes. The selection of materials in developing nanogenerator applications is vital in guaranteeing that the produced devices have decent output performance. Zinc oxide (ZnO) is a semiconductor material with a large bandgap that significantly influences numerous technological sectors, including nanogenerator fabrications. Besides, numerous methods have been used to synthesize ZnO nanostructures for various applications. The improvement and alterations need to be performed based on the produced ZnO nanostructures for better device performance. Previous studies have reported the effect of metal-doped ZnO nanostructures on the properties and characteristics of the nanogenerator applications. Hence, the brief review of the different techniques used in the fabrication of ZnO nanostructures and the performance enhancement of the ZnO-based nanogenerator, which consists of the doping process and the development of nanogenerator applications, have been presented in this paper.