Mg-doped ZnO Research Articles

Study of structural, morphological and optical properties of ZnO and Mg-doped ZnO thin films synthesized by evaporation technique

Un-doped ZnO and Mg-doped ZnO thin films (TFs) are synthesized by evaporation technique. The synthesized un-doped ZnO TFs are exposed to evaporated Mg contents for different times. XRD patterns reveal the development of (100), (002), (101) planes related to ZnO phase. The shifting of diffraction planes and shrinking of lattice parameters confirms the doping of Mg contents into ZnO lattice. The crystallite size of (100), (101) and (002) planes lies in the range from (12.43-14.51 nm), (14.28-19.08 nm) and (14.78- 19.19 nm) respectively. SEM analysis indicates that the formation of nano-fibers and nano-chains of rounded nanoparticles. EDX analysis confirms the presence of Zn, O and Mg whose amount is increased with increasing exposure time. The energy band gap (Eg) of un-doped ZnO (⁓ 3.05 eV) is increased to  3.08,  3.19 and  3.29 eV) with increasing exposure time in Mg contents.

Fabrication of Dye-Sensitized Solar Cells (DSSC) Using Mg-Doped ZnO as Photoanode and Extract of Rose Myrtle (Rhodomyrtus tomentosa) as Natural Dye

A dye-sensitized solar cell (DSSC) device using Mg-doped Zn thin films as photoanode and fruit extract of rose myrtle (Rhodomyrtus tomentosa) as the natural dye was investigated. The effect of annealing temperature (400-550°C) on the films of photoanode was systematically studied using an X-ray diffractometer (XRD), UV-Visible Near Infrared (UV-Vis NIR) Spectrophotometer, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). XRD confirm that all sample has the wurtzite hexagonal with crystallite size of 25 nm. The SEM images reveal particles on the surface of the Mg-doped ZnO thin film of irregular shapes. Increasing the annealing temperature leads to a larger particle size and slightly increases bandgap energy. The dye sensitizer of extracted rose myrtle (Rhodomyrtus tomentosa) has a strong absorption at the visible light region. The maximum efficiency of the DSSC device is 3.53% with Mg-ZnO photoanode annealed at 500°C.

Effects of Mg doping and annealing temperature on the performance of Mg-doped ZnO nanoparticle thin-film transistors

Mg-doped ZnO nanoparticle (NP) thin-film transistors (TFTs) were fabricated using a solution process under a range of Mg content and annealing temperature conditions. The effects of Mg doping and annealing on the electrical properties of the Mg-doped TFTs were investigated. The experimental results demonstrate that critical Mg doping and thermal annealing improve the electrical characteristics of the TFTs. It can mainly be attributed to the suppression of oxygen vacancy formation verified from X-ray photoelectron spectroscopy (XPS) analyses and Hall measurements.

High Performance Top-Emission Quantum Dot Light-Emitting Diodes with Mg-Doped ZnO Nanoparticles Used as an Electron Transport Layer.

In this paper, we reported superior performance of solution-processed top-emission quantum dot light-emitting diodes (TE-QLEDs) with Mg-doped ZnO nanoparticle (NP) electron transport layer (ETL). The Mg-doped ZnO NPs were synthesized by the sol-gel method. Transmission electron microscopy (TEM) analysis of the Mg-doped ZnO NPs with 0 wt%, 5 wt%, 10 wt%, and 15 wt% Mg-doping concentrations revealed average diameters of 5.86 nm, 5.33 nm, 4.52 nm, and 4.37 nm, respectively. The maximum luminance, the current efficiency, and external quantum efficiency (EQE) were 178,561.8 cd/m², 56.0 cd/A, and 14.43%, respectively. However, for the best performance of TE-QLED without Mg-doping in the ZnO NPs, the maximum luminance was only 101,523.4 cd/m², the luminous efficiency was 27.8 cd/A, and the EQE was 6.91%. The improvement of the performance is attributed to the suppression of electron transfer by an increase in the energy barrier between the cathode and Mg-doped ZnO NP ETL and the reduction in the Hall mobility of electron with increasing the Mg-doping in the ZnO NPs, resulting in the enhanced charge balance in the quantum dot (QD) emitting layer (EML).

Photoluminescence in gas of (Ca) Mg-doped ZnO nanopowders

The researches structural, morphological and photoluminescent properties of zinc oxide nanopowders doped by Mg and Ca obtained using pulsed laser reactive technology is carried out. Electron microscopy and X-ray diffractometry were conducted to determine the structure, shape, and size of the nanoparticles. Investigation of the peculiarities of photoluminescence in different ambient of Ca- and Mg-doped ZnO nanopowders was carried out. The decomposition of luminescence spectra into elementary bands shows the presence of four elementary peaks. The most intense two bands in visible region which are sensitive to ambient gas, a blue-band centered at 430 nm and stronger in intensity the band around 520 nm. The influence of the impurity and the different ambient on the redistribution of elementary luminescence bands intensities was investigated. That can be used in the gas sensors. The visible emissions observed may be ascribed to the intrinsic defects in particular oxygen vacancies. Large surface area and surface defects are the most important variables to determine the sensory properties of ZnO nanopowders and making them are the most favorable material for gas sensors.

Effects of ZnMgO Electron Transport Layer on the Performance of InP-Based Inverted Quantum Dot Light-Emitting Diodes.

An environment-friendly inverted indium phosphide red quantum dot light-emitting diode (InP QLED) was fabricated using Mg-doped zinc oxide (ZnMgO) as the electron transport layer (ETL). The effects of ZnMgO ETL on the performance of InP QLED were investigated. X-ray diffraction (XRD) analysis indicated that ZnMgO film has an amorphous structure, which is similar to zinc oxide (ZnO) film. Comparison of morphology between ZnO film and ZnMgO film demonstrated that Mg-doped ZnO film remains a high-quality surface (root mean square roughness: 0.86 nm) as smooth as ZnO film. The optical band gap and ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the conduction band of ZnO shifts to a more matched position with InP quantum dot after Mg-doping, resulting in the decrease in turn-on voltage from 2.51 to 2.32 V. In addition, the ratio of irradiation recombination of QLED increases from 7% to 25% using ZnMgO ETL, which can be attributed to reduction in trap state by introducing Mg ions into ZnO lattices. As a result, ZnMgO is a promising material to enhance the performance of inverted InP QLED. This work suggests that ZnMgO has the potential to improve the performance of QLED, which consists of the ITO/ETL/InP QDs/TCTA/MoO3/Al, and Mg-doping strategy is an efficient route to directionally regulate ZnO conduction bands.

Influence of magnesium doping on microstructure, optical and photocatalytic activity of zinc oxide thin films synthesis by sol–gel route

The article deals with the effect of Mg dopant on the properties and the photocatalytic of ZnO films synthesized by the sol–gel technique onto glass substrates. It is found that Mg dopant has a strong influence on the microstructure and functional properties. The EDX analysis revealed that Mg had been incorporated into the ZnO. Structural studies through XRD have shown that the deposited films are of hexagonal structure with a preferential growth along the c-axis and nanometer crystal size. According to AFM analysis; it is found that the roughness of Mg-doped ZnO films increases with the Mg dopant. The film surface depicted wrinkles morphology as observed by ESEM. Optical investigations by spectrophotometry and photoluminescence revealed that as the Mg dopant is increased, the optical band-gap increases. Moreover, near band edge and visible emissions as probed by Photoluminescence can be manipulated by the Mg dopant, as their intensity increases and decreases, respectively. Finally, the photocatalytic activity for degradation of methylene blue is strongly improved all the more as the Mg content is increased.

Elaboration and Characterization of Mg-Doped ZnO Thin Films by Thermal Evaporation: Annealing Temperature Effect

The annealing temperature effect on the structural, optical, electrical, and mechanical properties of different samples based on ZnO-Mg (MZO) thin films has been investigated. The studied samples were annealed at 300, 400, and 500 °C at atmospheric pressure, and the reference ones were kept without annealing. X-ray diffraction (XRD) analysis confirmed the growth of ZnO hexagonal wurtzite structure at 300 °C, while an increase in the structure crystallinity was observed at 500 °C. Electron-dispersive spectroscopy (EDS) analysis shows the existence of Zn, O, and Mg elements. The Raman spectroscopy reveals the appearance of A1(LO) and LVM modes for all samples. Transmittance spectra in the visible range show an increase in layer transmittance as function of annealing temperature. Similarly, the optical band gap rises from 3.40 to 3.61 eV. The electrical resistance measurements indicate that the as-deposited MZO are conductive films. However, the obtained resistance values for post-annealed MZO confirm the semiconductor behavior of the layer. Results from the mechanical characterization of MZO films, and particularly the proportional relation between hardness and grain size according to the annealing temperature, revealed a behavior disagreement with the Hall-Petch formula.

Synthesis and Characterization of Undoped and Magnesium Doped Zinc Oxide Nanoparticles

Undoped and Mg-doped ZnO nanoparticles were synthesized by co-precipitation method. The synthesized nanoparticles are successfully characterized by XRD, SEM, and UV-visible analysis. The Structure, Morphology, and Optical activity of the synthesized nanoparticle were studied with respect to ZnxMg1-xO (where x= 0, 2.5%M and 7.5%M). The XRD patterns revealed the wurtzite structure for all the nano samples. XRD studies confirmed that the crystalline size increased with increase in Mg content. The surface morphology of the prepared pure and Mg doped ZnO nanoparticles are investigated by SEM analysis. Optical characterization reveals that band gap energy decreases from 3.24 to 3.13 eV with Mg doping. UV-Visible results revealed that absorption underwent a red shift with Mg into ZnO as compared to pure ZnO.

Rare-class learning over Mg-doped ZnO nanoparticles

This interdisciplinary study is conducted to find answers to two important questions which researchers often face in Machine Learning (ML) and Material Science (MS) fields. In this work, we measure the performance of the most popular ML algorithms (more than a dozen) on rare-class learning problem and determine the best learning algorithm for atom type prediction over the Mg-doped ZnO nanoparticles data obtained from the density-functional tight-binding method. As a result, we observe that tree-based ML algorithms such as Extreme Gradient Boosting (XGB), Decision Trees (DT), Random Forest (RF), outperform other types of ML algorithms, e.g., cost-sensitive learning, prototype models, support vector machines, kernel methods, on both rare-class learning and atom type prediction.

Nanoparticles of ZnO and Mg-doped ZnO: Synthesis, characterization and efficient removal of methyl orange (MO) from aqueous solution

Nanoparticles of zinc oxide and of ZnO doped with MgO in different concentrations (1, 2 and 4 mol%) were synthesized in a controlled and reproducible way, using the Pechini polymer precursor method. To determine the physicochemical and structural characteristics of the synthesized nanoparticles, Fourier transform IR (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy and transmission and scanning electron microscopy (TEM and SEM) were used. Characterization revealed the particles obtained to be nanometric in size (<50 nm) and with a deformed hexagonal morphology. Taking into account the doping percentage, the energy gap value varied between 3.3 eV for pure ZnO and 3.45 eV for ZnO with 4 mol% of Mg, which indicates that the optical properties of these nanoparticles were affected by dopant concentration. The effect of doping with Mg2+ on the capacity for removal of pollutant molecules by ZnO, for different working conditions, was evaluated by studying the removal of methyl orange (MO) in aqueous solution. Irradiation of the compounds led to a greater removal of MO from the solution such that all ZnO samples doped with MgO showed higher photoactivity than ZnO. The ZnO nanoparticles doped with 2% Mg were the most efficient in removing MO, achieving a removal percentage of ~73% after 2 h of testing and a totally transparent solution after 3 h of treatment. The kinetics of removal of MO promoted by this sample was best represented by pseudo-first-order kinetics. The results of this work showed that on combining a photosensitive semiconductor, ZnO, with a wide band gap insulator, MgO, Zn–Mg solid solutions are obtained that showed adequate capacity to remove contaminating organic molecules, specifically MO.

The influence of H2O and O2 on the optoelectronic properties of inverted quantum-dot light-emitting diodes

The influence of H2O and O2 on the performances of Mg-doped zinc oxide (ZnMgO) and ZnMgO-based inverted quantum-dot light-emitting diodes (QLEDs) are studied. With the involvement of H2O from ambience, ZnMgO exhibits a high conductivity, whereas the resultant QLEDs show a low efficiency. The efficiency of QLEDs can be enhanced by annealing ZnMgO in H2O-free glovebox; however, the uniformity and the current of the devices are degraded due to the presence of O2, which adsorbs on the surface of ZnMgO and captures the free electrons of ZnMgO. By exposing the devices with ultraviolet (UV) irradiation, the adsorbed O2 can be released, consequently leading to the increase of driving current. Our work discloses the influence of the annealing ambience on the conductivity of ZnMgO, and reveals the interaction of H2O/O2 and UV with the ZnMgO and its effect on the performance of the resultant inverted QLEDs, which could help the community to better understand the mechanisms of ZnMgO-based QLEDs.

Effect of Mg content on electronic structure, optical and structural properties of amorphous ZnO nanoparticles: A DFTB study

In this work, we perform a theoretical analysis of structural, electronic, and optical properties of pure and Mg-doped amorphous ZnO nanoparticles (a-ZnO NPs) using DFTB method. Our results show that Zn atoms are more preferential for Mg atoms than for O atoms because the number of MgZn bonds is greater than that of MgO. The rise in the content of Mg in a-ZnO NPs leads to an increase of Mg–Zn and MgO interactions. Mg atoms prefer to locate near the center of a-ZnO NP, but Zn and O atoms nearly preserve their positions which is compatible with radial distribution function peaks. The orbital energies display a decrease in the energy gap from 3.592 to 3.546 eV while increasing Mg content. The LUMO level is also significantly shifted to higher energies. The results also reveal that the performance of pure a-ZnO NP can be enhanced with a subsequent increase in Mg content.

Enhanced photosensing by Mg-doped ZnO hexagonal rods via a feasible chemical route

One-Dimensional (1D) pure-ZnO, Zn0.9Mg0.1O and Zn0.8Mg0.2O thin films have been successfully grown over a glass substrate using simple economical chemical bath deposition method (CBD). This investigation explores the enhancement in photocurrent and photosensitivity of Zn1−xMgxO thin films via induced defects with vertically aligned hexagonal rod-like array thin films. The structural, optical and electrical properties of the synthesized materials have been elucidated using X-ray Diffraction (XRD), Raman, UV–Vis spectroscopy, Photoluminescence (PL), and I–V characteristics. Hexagonal rod-like morphology has been confirmed from both XRD and SEM results. Change in structural properties revealed that the formation of the Mg(OH)2 phase for Zn1−xMgxO thin films from XRD spectra. Thus, the impact of extra Magnesium (Mg) which is difficult to incorporate in ZnO lattice sites which causes the phase segregation and possibly creates morphological and structural defects. This has been also confirmed from electron–phonon interaction in Raman analysis. Such as the Raman-shift of E2 (high) mode in Zn1−xMgxO thin films towards higher frequencies indicates the substitution of Mg at O lattice sites. However the formation of phase segregation had a significant effect on optical as well as electrical properties of the ZnO hexagonal rods thin films. From UV–Vis spectra, the intensity of absorption edges for Mg-doped samples are decreases while the optical band gaps are increases from 2.87 to 3.47 eV and also from PL spectrum shows that the defect states in visible range are increases with increasing Mg content in ZnO. The parameters like photocurrent and electrical resistance are calculated from I–V characteristics and the results shows that the photosensitivity enhanced as Mg content increases in ZnO.

Impact of particle size and surface defects on antibacterial and photocatalytic activities of undoped and Mg-doped ZnO nanoparticles, biosynthesized using one-step simple process

One-step simple process was used to biosynthesis Zn1−xMgxO (x = 0, 0.01, 0.03 and 0.05) nanoparticles. Structural, morphological, optical, elemental and chemical composition of all the samples were explored with XRD, SEM, UV–vis, EDS and FT-IR spectroscopy respectively. The XRD results showed decrease in average crystallite size (51–37 nm), lattice constants “a & c”, bond length and volume of unit cell, as well as increase in micro-strain and dislocation density as Mg content is increased from 0 to 5%. The energy band-gap increased from 3.30 to 3.40 eV with increment in Mg concentration up to 5%. The antimicrobial and photcatalytic results clearly indicated that Mg-doped samples improved bacterial inhibition zones and photocatalytic degradation efficiency. The observed improvement in antimicrobial and photocatalytic activities are attributed surface defect and larger surface area. The result implies that doped samples could be more effective in inhibition of bacterial biofilm growth on surfaces and photocatalyst detoxification applications.

Effect of Mg doping on ZnO fabricated using aqueous leaf extract of Ziziphus mauritiana Lam. for antioxidant and antibacterial studies.

Aqueous leaf extract of Ziziphus mauritiana Lam. was successfully used to synthesize zinc oxide (ZnO) and magnesium-doped ZnO (Mg-doped ZnO) particles and acted as capping and stabilizing agent. UV-Vis diffuse reflectance spectra showed that optical band gap energy of ZnO has narrowed from 3.11 to 3.08eV and 3.03eV when doped with 1% Mg and 5% Mg, respectively. Powder X-ray diffraction and X-ray photoelectron spectroscopy studies confirmed the purity and crystalline nature of the synthesized materials. FT-IR spectroscopy revealed the presence of phytochemicals coated on the surface of synthesized materials. The synthesized materials were found to effectively scavenge DPPH radicals in the presence of visible light in comparison to the dark. The antibacterial properties of the synthesized materials were evaluated against Staphylococcus aureus and Escherichia coli. The obtained results revealed that Staphylococcus aureus seemed to be more sensitive to the green synthesized ZnO and Mg-doped ZnO than Escherichia coli.

Electrochemical Synthesis of Mg-doped ZnO Nanotapers as Photocatalyst for Degradation of Bisphenol under Solar Light Irradiation

Electrochemical Synthesis of Mg-doped ZnO Nanotapers as Photocatalyst for Degradation of Bisphenol under Solar Light Irradiation

TL Characteristics and Dosimetric Aspects of Mg-Doped ZnO

Dosimetry characterization and the evaluation of kinetics parameters of trapping states of Mg-doped ZnO phosphors synthesized by Sol-Gel technique. The thermoluminescence response of Mg-doped ZnO samples showed a linear response when exposed to X-ray radiation and the optimum annealing condition was 400oC/4h for the three concentrations. A broad-shaped TL glow curve with an upper bound of 270 °C, which shifts to lower temperatures with increasing dose, indicating that general order (GO) kinetics thermoluminescence processes are involved. We conclude that the ZnO doped Mg phosphors under study are promises to develop dosimeters for high radiation dose measurements. Kinetic parameters, such as activation energy (E), frequency factor (s), and order of kinematic order (b), were estimated by the Glow Curve Deconvolution (GCD) method. ZnO:Mg phosphor has a great potential as a dosimeter for monitoring in the fields of ionizing radiation.

Efficient PbS Quantum Dot Solar Cells with Both Mg-Doped ZnO Window Layer and ZnO Nanocrystal Interface Passivation Layer.

In this paper, a Mg-doped ZnO (MZO) thin film is prepared by a simple solution process under ambient conditions and is used as the window layer for PbS solar cells due to a wide n-type bandgap. Moreover, a thin layer of ZnO nanocrystals (NCs) was deposited on the MZO to reduce carrier recombination at the interface for inverted PbS quantum dot solar cells with the configuration Indium Tin Oxides (ITO)/MZO/ZnO NC (w/o)/PbS/Au. The effect of film thickness and annealing temperature of MZO and ZnO NC on the performance of PbS quantum dot solar cells was investigated in detail. It was found that without the ZnO NC thin layer, the highest power conversion efficiency(PCE) of 5.52% was obtained in the case of a device with an MZO thickness of 50 nm. When a thin layer of ZnO NC was introduced between MZO and PbS quantum dot film, the PCE of the champion device was greatly improved to 7.06% due to the decreased interface recombination. The usage of the MZO buffer layer along with the ZnO NC interface passivation technique is expected to further improve the performance of quantum dot solar cells.

Influence of Substrate Temperature and Magnesium Content on Morphology Evolution and Luminescence of Mg-doped ZnO Films

Influence of Substrate Temperature and Magnesium Content on Morphology Evolution and Luminescence of Mg-doped ZnO Films