Co-doped ZnO Samples Research Articles

Wedge-shape Al and Mg co-doped zinc oxide thin films: A Facile Route to achieve high thermoelectric power factor

Thin film thermoelectric technology has immense potential to become a next-generation power source for small-scale electronics. However, the rapid development of thin film thermoelectric still lacks a controllable structural design to improve the performance of thermoelectric devices for required temperature applications. This work presented a controlled thermoelectric design of ZnO-based thin films by Al and Mg co-doping using ALD. Herein, the Mg-doped ZnO sample exhibits the highest Seebeck coefficient of −311.83 μVK−1 at 500oC, while the maximum thermoelectric power factor of 3.68 μWcm−1K−2 is obtained at 300oC, which drops for higher temperatures. This decrease in power factor resulted from the reduction in electrical conductivity above 300oC. Similarly, the Al and Mg co-doped ZnO sample (Mg/Al ≈2 at%) exhibits a high thermoelectric power factor of 3.85 μWcm−1K−2 for ZnO based material due to its moderate electrical conductivity and Seebeck coefficient value at 325oC and behave monotonically for elevated temperatures. Scanning electron microscope (SEM) images show the formation of wedge-shaped structures for Al-incorporated samples, which helps to boost the overall thermoelectric performance. Additionally, we performed XRD, UV–Vis, Hall, and AFM analysis to get a deep insight into structural, optical, electrical, and surface features of the grown thin films and their linkage with the thermoelectric properties.

Synthesis, characterization, and dielectricity performance of bulk pristine Fe3+ and Li+ Co-substituted wurtzite ZnO

High dielectric constant materials are of technological importance as they lead to the miniaturization of electronic devices. The permittivity of a material determines the relative speed that an electrical signal can travel in that material. The dielectric properties of pure ZnO are developed due to the defects of zinc excess at the interstitial position and the lack of oxidation. Fe and Li co-doping in ZnO are envisaged here to develop high dielectric materials by converting the material into a p-type semiconductor without creating stoichiometric oxygen defects in the lattice and making it robust against the oxidizing atmosphere. The formation of single-phase Fe and Fe/Li co-doped wurtzite ZnO samples is confirmed by X-ray diffraction analysis. The Fe and Fe/Li doping depresses the concentration of the intrinsic donor and impedes the conduction mechanism resulting in the highest dielectric constant (ɛr′) equivalent to 612 and 90,000 are found for bulk pristine Zn0.9Fe0.1O and Zn0.8Li0.1Fe0.1O at 400oC with 1000 ​Hz applied frequency. Also with an increase in frequency, the dielectric constant and dielectric loss are found to decrease. This behavior is attributed to different hopping mechanisms and defects formed during synthesis.

Combustion synthesis of Ce/Mg co-doped ZnO nanoparticles as a visible-light-driven photocatalyst

ZnO and Ce/Mg co-doped ZnO nanoparticles as a visible-light-driven photocatalyst were synthesized by combustion method. X-ray diffraction (XRD) patterns of ZnO and Ce/Mg co-doped ZnO samples were indexed to the pure phase of hexagonal wurtzite ZnO structure without impurity detection. The Raman analysis of ZnO and Ce/Mg co-doped ZnO samples showed optical phonon E2H, A1(TO), E2L, E2H–E2L, A1(LO) and E1(LO) modes of wurtzite ZnO structure, including the detection of Zn−O stretching mode containing in FTIR spectra of hexagonal wurtzite ZnO. Transmission electron microscopic (TEM) images of ZnO and Ce/Mg co-doped ZnO samples showed uniform and good distribution of nanoparticles with different orientations. The photocatalysis of ZnO and Ce/Mg co-doped ZnO nanoparticles was studied through the degradation of methylene blue (MB) illuminated by visible radiation. In this research, the Zn0.97Ce0.015Mg0.015O nanoparticles have the highest efficiency of 95.16% within 150 min because of the largest specific surface area, smallest crystallite size and highest absorption capacity of visible light for active species production in degrading of MB under visible light. Photocatalytic mechanism of Ce/Mg co-doped ZnO nanoparticles in degrading MB was also proposed.

Synthesis, characterization, DFT calculations, and anticancer properties of VI-period and f-block elements-substituted zinc oxide nanopowders

Nanotechnology provides promising ways in which a wide range of new materials can be manufactured which appear to have enormous potential in the field of biomedicine and life sciences. ZnO can be applied in many physical and optical processes and used as a good anti-cancer agent. ZnO NPs are recognized as SAFE or GRAS, non-toxic and biocompatible particles. In this study, wurtzite ZnO samples co-doped by rare earth elements (Tb, Er) were prepared via sol-gel auto-combustion route and their crystallographic structure as well as their morphologies were examined using XRD and TEM techniques. The analysis disclosed that all synthesized products crystallized in a hexagonal structure and the crystallites/particles size diminished with the increase of co-doping content. The electronic structure and optical properties of the different products were assessed using DFT calculations. Doping Tb and Er rare earth elements into ZnO has a significant effect on its optoelectronic properties. The computational study showed that the co-doping of Tb and Er on pure ZnO decreased the band gap and increased the refractive index. The extinction spectrum of pristine ZnO showed a peak in the ultraviolet region at 5 eV, while those of the co-doped ZnO samples displayed stronger peaks in the infrared region (near 0.4 eV). The anticancer properties of Tb/Er co-doped ZnO nanoparticles were examined on cervical cancer (HeLa cells) and colon cancer (HCT-116) by using an in vitro MTT assay. The cell viability assay findings indicated a reduction in HeLa and HCT-116 cells after 48 h of treatment of the synthesized samples. The treatment with co-doped ZnO nanoparticles produced chromatin condensation and formation of apoptotic bodies in HCT-166 cells, which indicates that the prepared co-doped ZnO nanoparticles induced programmed cell death in HCT-116 cells. According to these results, it can be concluded that the prepared Tb/Er co-doped ZnO nanoparticles have promising applications in developing new optoelectronic devices and also in treating cervical and colon cancers.

Insight into the role of Mg/B and Mg/Cu dual dopant on the properties of ZnO nanoparticles prepared by facile one-step combustion route for photocatalytic and antibacterial application

ZnO semiconductors are widely known to have benefits in photocatalytic and antibacterial applications. In this study, (Mg/B)–ZnO and (Mg/Cu)–ZnO were synthesized using the combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The XRD results confirmed a decrease in the crystal size and an increase in the crystallinity of the doped ZnO samples. SEM analysis confirmed the morphological changes in the structure from rod-shaped to spherical, and the particle size decreased in the doped ZnO samples. EDS analysis validated the nanoparticle composition of Zn, O, Mg, B, and Cu without impurities. Raman spectra confirmed the formation of defects due to the substitution of dopants in the ZnO lattice. All samples for FTIR analysis showed functional chemical group vibrations from Zn–O, C–H, and O–H stretching. The existence of dopant bonds with oxygen was also validated from this analysis. The change in band gap energy was observed from 3.13 to 3.10 eV in Mg/Cu–ZnO and 3.12 eV in Mg/B–ZnO sample due to the influence of the addition of dopant ions. The XPS spectra show the chemical composition of the nanoparticle samples and the oxidation numbers that correlate with the results of EDS and XRD analyses. A decrease in the emission intensity in the PL measurement was observed in the green emission region in the Mg/B–ZnO sample, which correlated with the decrease in electron recombination. The Photocatalytic application was performed by measuring its ability to degrade methyl violet dye under visible-light irradiation. The maximum deterioration after 120 min of irradiation was obtained for the Mg/Cu–ZnO, Mg/B–ZnO, and ZnO samples at 92.62 %, 92.20 %, and 80.89 %, respectively. Antibacterial activity increased against S. aureus bacteria in co-doped ZnO samples with inhibition zones of 12.15 mm, 8.15 mm, and 6.45 mm for Mg/B–ZnO, Mg/Cu–ZnO, and ZnO samples, respectively.

Combustion synthesis and characterization of visible-light-driven La/Al co-doped ZnO nanoparticles used for wastewater treatment

Visible-light-driven LaxAl0.03-xZn0.97O (x = 0.01, 0.015 and 0.02) nanoparticles were synthesized by tartaric acid-assisted combustion method. Both ZnO and La/Al co-doped ZnO samples were indexed to the pure hexagonal wurtzite ZnO structure and were composed of nanoparticles with particle size ranges of 100-150 nm and 20-50 nm, respectively. The photocatalytic activities of ZnO and LaxAl0.03-xZn0.97O (x = 0.01, 0.015 and 0.02) nanoparticles were monitored through the degradation of methylene blue (MB) under visible light irradiation. The La0.02Al0.01Zn0.97O nanoparticles have the highest photocatalytic activity in degrading of MB under visible light irradiation because the La/Al co-dopant played the role in creating shallow energy level under the conduction band of ZnO.

On the vibrational properties of transition metal doped ZnO: Surface, defect, and bandgap engineering

We present a comprehensive study on the structure and optical properties of Mn-and Co-doped ZnO samples prepared via solid-state reaction method with different dopant concentrations and atmospheres. The samples were structural and chemically characterized via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray excited photoelectron spectroscopy. The optical characterization was performed via Raman, photoluminescence, and diffuse photoreflectance spectroscopies. Emphasis was done on the studies of their vibrational properties. The structural data confirm the incorporation of Mn and Co ions into the wurtzite ZnO lattice. It is demonstrated that the usual observed additional bands in the Raman spectrum of transitional metal (TM) doped ZnO are related to structural damage, deriving from the doping process, and surface effects. The promoted surface optical phonons (SOP) are of Fröhlich character and, together with the longitudinal optical (LO) polar phonons, are directly dependent on the ZnO electronic structure. The enhancement of SOP and LO modes with TM-doping is explained in terms of nonhomogeneous doping, with the dopants concentrating mainly on the surface of grains, and a resonance effect due to the decrease of the ZnO bandgap promoted by the introduction of the 3d TM levels within the ZnO bandgap. We also discuss the origin of the controversial vibrational mode commonly observed in the Mn-doped ZnO system. It is stated that the observation of the analyzed vibrational properties is a signature of substitutional doping of the ZnO structure with tuning of ZnO optical absorption into the visible range of the electromagnetic spectrum.

Effective role of vibrational annealing in enhancing room temperature physical properties of Co doped ZnO nanoparticles by using novel TVA technique

Well-annealed nanocrystalline semiconductor materials in pellet or thin film form, composed of small grains with a high surface-to-volume ratio, are considered as promising candidates for multiple device applications. However, no such method is available yet that can control the grain size of such samples during heat treatment. In this present work, a novel thermo-vibrational annealing (TVA) setup for processing nanocrystalline materials was designed and fabricated in-house. Here both thermal and mechanical vibrational energy were simultaneously applied to the sample during annealing, followed by vibrational dry quenching in the presence of an inert gas environment. Co-doped ZnO pellets were synthesized by chemical route pyrophoric method followed by annealing at 800 °C for 4 h using this set up. For comparison, one pellet was annealed with vibration with calibrated vibration at a speed of 360 rpm, and another pellet was annealed without vibration. X-ray diffraction (XRD), Raman and Fourier transform Infrared (FTIR) spectroscopic studies showed the formation of a single crystalline phase with hexagonal wurtzite structure of both the samples and the proper incorporation of Co2+ ions into the ZnO matrix without any impurity phases, which was also confirmed by energy dispersive X-ray (EDX) spectroscopy studies. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) studies confirmed the decrease in average grain and particle size of the sample when processed with the TVA setup. Ultraviolet–Visible spectra showed that the bandgap energy of the Co-doped ZnO sample varies inversely with particle size. Hall-effect measurements demonstrated the semiconducting nature of both samples with n-type charge carriers. The presence of Co2+ ions in the wurtzite ZnO lattice was confirmed by X-ray photoelectron spectroscopy (XPS). The magnetic properties were studied using a SQUID magnetometer, which confirmed that a Co doped ZnO sample annealed with the TVA technique exhibit better room temperature ferromagnetism properties compared to sample annealed without vibration. Based on these studies, it was believed that the sample annealed by mechanical vibrational energy with vibrational dry quenching has a great influence on several physical properties of any material and hence Co doped ZnO sample processed with this TVA technique can be used as a promising candidate for multiple sensor and magnetic storage devices.

Ferromagnetic ordering in Co-Sm co-doped ZnO prismoids grown by co-precipitation method

• Co-precipitation method is used to synthesize Co-Sm co-doped ZnO sample. • The crystallinity of the sample enhanced on adding Co dopant into ZnO matrix. • Prismoid structure is observed for CZ and CSZ1 samples. • CSZ1 sample showed strong superparamagnetic with weak ferromagnetic ordering. The current study illustrates the impact of defects on magnetic behaviour of the ZnO based samples. We examined the structural, luminescent, and magnetic properties of Co-Sm co-doped ZnO nano powder synthesized using the co-precipitation method. X-ray diffraction (XRD) and a Raman study were carried to understand the structural properties. The XRD results showed that all the prepared samples exhibited wurtzite phase with no impurity peaks. The same was reflected in the Raman study along with disorder induced band indicating enhanced defects sites on doping and co-doping. The presence of defects in the prepared samples was further confirmed using photoluminescence characterization. The morphological study confirms the prismoid structures in Co doped, and Co and Sm co-doped ZnO samples. A vibrating sample magnetometer (VSM) was used to investigate the magnetic properties of the samples at room temperature, which showed the coexistence of superparamagnetic and weak ferromagnetic ordering in doped/co-doped samples. The formation of defects in prismoid structures enhanced the magnetic behaviour of the samples. The evolution of ferromagnetic ordering in doped/co-doped samples due to defect states was discussed in detail.

Synthesis of multifunctional Cu and Al codoped ZnO nanoparticles towards photosensor and photocatalytic applications

Cu–Al codoped ZnO nanocomposites were prepared via the simple wet chemical method. The XRD revealed the crystal structure and effect of Cu and Al dopants in the ZnO lattice, such as decrement of crystallite size and increment of microstrain were determined. Surface morphology of the samples was examined by FESEM measurement. FTIR and EDX spectra confirmed the presence of Cu and Al dopants in the ZnO. The optical properties of the pure, Cu, Al-doped ZnO and Cu–Al codoped ZnO nanocomposites were studied by diffused reflectance spectroscopy, and their optical band gaps were determined. The P.L. studies of the prepared sample showed that the P.L. intensity decreased slightly for Cu–Al codoped ZnO. The photosensing behavior of the sample was studied, and its essential properties such as Responsivity (R), detectivity (D*), and External Quantum Efficiency (EQE) of the Cu–Al codoped ZnO sample were found to be 6.96 x 10−2 AW−1, 5.30 x 109 Jones and 16.2% respectively. The photocatalytic degradation of M.B. dye was analyzed, photodegradation efficiency and rate constant of the Cu–Al codoped ZnO sample is 88% and 0.0237 min−1 respectively.

Magnetic properties in randomly diluted magnetic systems: Co-doped ZnO polycrystalline ceramics

The influence of structural defects on the magnetic properties of Co-doped ZnO polycrystalline ceramics (Zn1−xCoxO) with 0.00 ≤ x ≤ 0.05 sintered by a pressure-less solid state reaction method were investigated in a broad range of temperatures (5 ≤ T ≤ 300 K) for applied magnetic fields up to 85 kOe. The hysteresis loops indicated the presence of diamagnetic behavior for undoped ZnO samples while both antiferromagnetic (AFM) and paramagnetic (PM) ordering for Co-doped ZnO. The saturation magnetization Ms values decrease with increasing Co concentration (x), being ~ 2.5 μB∕Co and ~ 1.6 μB∕Co for x = 0.005 and x = 0.05, respectively, T = 5 K. Also the fraction of the saturation magnetization values were found to be 0.83 (83 % PM), 0.66 (66 % PM) and 0.62 (62 % PM) for samples (x) 0.005, 0.02, and 0.05, respectively. The decrease of PM ordering with x, could be attributed to the shortening the distance between adjacent Co ions which favor the AFM coupling due to super-exchange interaction. In addition, the Jex∕kB values were found to be negative, being − 20, − 30, and − 31 for x = 0.005, 0.02, and 0.05, respectively, indicated the absence of FM coupling for all Co-doped ZnO samples. The reduction in Jex∕kB values are due to the increase of AFM ordering for Co ions homogeneously diluted in the ZnO structure during sintering process at high temperatures (≥1100 °C). Even though the presence of a large number of structural defects in both pure and doped ZnO ceramic samples reveled by Raman and UV-Vis spectroscopy analysis the ferromagnetic (FM) ordering was not present for the broad range of temperatures (5 ≤ T ≤ 300 K) studied.

Al and B co-doped ZnO samples as an alternative to ITO for transparent electronics applications

Al and B co-doped ZnO samples as an alternative to ITO for transparent electronics applications

Effect of yttrium substitution in Fe-doped ZnO nanoparticles: An EPR study

In this work, we investigated the effect of Y3+ inclusion in ZnO nanoparticles doped with Fe3+ synthesized by the sol gel method. Transmission Electron Microscopy (TEM) images showed agglomerated nanostructures with different shapes and average particle size distributions ranging from 6 nm to 44 nm in diameter. Electron Paramagnetic Resonance (EPR) studies of the Zn0.98−yY0.02FeyO (y=0.00, 0.02, 0.03 and 0.04) were carried out using X band (9.7 GHz) at room temperature. For undoped ZnO and doped with Y3+, complex line shapes were observed as a result of oxygen vacancies (VO+1). In addition, the Y3+ inclusion provokes an enhancement of the linewidth and the resonance field due to intrinsic defects in the hexagonal structure. This observation is compatible with a shortest relaxation time by reason of the particle size reduction and an extra antiferromagnetic local field as a result of the Y3+ presence. For co-doped ZnO samples, the EPR spectra confirms the presence of Fe3+ and Y3+ at the core Zn sites, altering the lattice strain of the ZnO structure. This result was monitored by the zero-field splitting (ZFS) parameters of the spin Hamiltonian, corroborating a reduction in the Fe - Fe interaction. The presence of Y ions was also confirmed in interstitial sites, resulting in a small g-shift from 4.2 to 4.0 associated with modifications of the rhombic component, E, of the Spin–Hamiltonian. This study contributes to the understanding of structural defects caused by the Y and Fe inclusion in the Wurtzite crystal structure of ZnO, a material with potential applications in spintronic devices.

Effects of Bi and S co-doping on the enhanced photoelectric performance of ZnO: Theoretical and experimental investigations

The enhanced photoelectric performance of (Bi, S) co-doping ZnO is explored by combining the density functional theory (DFT) calculations with experimental measurements. The crystal structures, formation energies, electronic properties and relative effective mass of photogenerated electrons and holes of pure and (Bi, S) co-doped ZnO are investigated by DFT calculations. Results indicate that Bi/S co-doping can generate impurity states and shift the conduction band into the lower energy region, causing the decrease in band gap. Relative effective mass show that the separation rates of photogenerated carriers are enhanced after modification. Moreover, experimental measurements are carried out on the basis of the above theoretical analysis. Pure and Bi/S co-doped ZnO samples with different doping ratios are synthesized and characterized. The results confirm that the presence of (Bi, S) has major effects on oxygen defects in crystal structure. XPS, UV–vis and PL studies evidence the roles of these oxygen defects on band gap narrowing for 2% ZnO samples. As expected, 2% doping sample has the highest photocurrent value (23.58 μA cm−2, nearly 4.7 times higher than pure ZnO) and the smallest Nyquist semicircle diameter. This work will provide some new insights into the design of high performance photoelectrocatalysis materials.

Photodegradation of tartrazine dye favored by natural sunlight on pure and (Ce, Ag) co-doped ZnO catalysts.

In this work, the synthesis of pure and (Ce, Ag) co-doped ZnO was successfully accomplished using a solvothermal process. The synthesized samples were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, and scanning electron microscopy. The photocatalytic ability of the samples is estimated through degradation of tartrazine in aqueous solution under photocatalytic conditions. The degradation study carried out for a reaction period of 90 min at and a free pH = 6.0 found that dye degradation is 44.82% for pure ZnO and 98.91% for (Ce, Ag) co-doped ZnO samples, indicating its excellent photocatalytic ability. Tartrazine mineralization was also studied by calculating the degradation of chemical oxygen demand. The effect of operating parameters such as catalyst dose, initial concentration of tartrazine, initial reaction pH, and nature of light source has been optimized for tartrazine degradation as a function of time. The reusability of ZnO and (Ce, Ag) co-doped ZnO catalysts was studied and its photocatalytic efficiency was found to be unchanged, even after six cycles of use. The mechanism of photocatalytic activity was also proposed.

Enhancement of optical, dielectric and transport properties of (Sm, V) co-doped ZnO system and structure-property correlations

In this work, V-doped and (Sm, V) co-doped ZnO samples have been synthesized using ball milling method followed by heat treatment. The dependence of structural, optical, electrical and dielectric properties of V:ZnO samples on the Sm doping concentration has been explored. The structural properties have been studied by means of X-ray diffraction (XRD) and Rietveld refinement. Oxidation states of the elements present in the samples are determined using X-ray photoelectron spectroscopy. Raman spectra of the samples further verified the observations obtained from XRD. The crystallite size and microstrain have been estimated from the Williamson-Hall analysis. Microstrain increases from 0.814 × 10−3 to 1.01 × 10−3 with increase in the Sm doping level. The morphology of the grains is significantly affected by the Sm doping. The enhancement of defect density with Sm doping is responsible for the observed red shift (3.29–3.19 eV) in the band gap. The frequency dependence of the dielectric properties has been studied at various fixed temperatures ranging from 25 to 350 °C. The increase in real dielectric constant with dopant content indicates the enhancement of energy storage capacity. The ac conductivity follows Jonscher's power law and it increases up to 1 mol% Sm concentration. Further increase in Sm extent leads to the decrease in ac conductivity. The impedance spectroscopy has been performed to understand electrical behavior of samples and Cole-Cole plots are fitted against the equivalent circuit model. The electrical activation energy values for conduction and relaxation vary in the range: 0.281–0.269 eV and 0.260–0.243 eV, respectively.

Mutual effect of solvent and Fe-In codoping on structural, optical and electronic properties of ZnO thin films prepared by spray pyrolysis technique

This work demonstrates a comparative analysis of structural, morphological, optical and electronic properties of ZnO thin films with respect to change in solvent composition as well as relative codoping concentration of Fe and In. Two different solvent compositions are used i.e. methanol mixed with de-ionized water (methanol-water) and only de-ionized water. X-ray diffraction analysis shows methanol-water solvent resulting preferred orientation along (002) plane. However, de-ionized water derived ZnO samples depicts the usual three most intense peaks along (100), (002) and (101) planes as in case of zincite. There is also observed a change in morphology of the films e.g. flake like nanoparticles are found in 1 at.% Fe and 3at.% In co-doped ZnO thin films synthesized using methanol-water only. Room temperature photoluminescence emission spectra show evolution of a strong emission at 415 nm in case of low doping concentration of Fe (1–3 at.%) in codoped ZnO samples.

Effect of Fe-In co-doping on microstructural, optical, electrical and LPG response properties of spray pyrolytic ZnO thin films

Abstract This work investigates the microstructure, optical absorption, electrical resistivity and LPG (Liquefied Petroleum Gas) response of ZnO thin film with the change in relative doping concentrations of In and Fe in the host lattice. All the films retain polycrystalline nature with hexagonal wurtzite unit cell structure. Scanning electron microscopic study reveals that regular spherical shaped nanoparticles are formed in undoped ZnO, but a compact surface morphology has obtained in case of 3 at.% In doped ZnO (IZO) thin films owing to the reduction in particle size. In the case of 1 at.% Fe co-doping in IZO, nano-flakes are formed. However, at higher Fe doping concentration, this typical particle morphology gradually changes to spherical shapes again. By comparing the energy dispersive X-ray analysis data, the formation of flakes type nanostructures is attributed to the presence of excess oxygen in the sample and it dominates the thermally activated conductivity phenomenon in the low temperature range. Fe-In co-doping results low optical transmittance and reduction in the band gap of ZnO. It also lowers the conductivity in IZO thin film. IZO thin film samples exhibit better LPG response than ZnO and Fe-In co-doped ZnO samples owing to its smaller particle size.

Magneto-Opto Electronic Applications of Conductive and Room Temperature Ferromagnetic (Al, Mn) Co-Doped ZnO Particles with Visible Emission.

The Mn, Al co-doped ZnO samples were synthesized using solid-state reaction method and were annealed in furnace at 300 °C, 600 °C and 900°C temperature. All the samples prepared were investigated in detail for analysis of their structural, morphological, optical, magnetic and electrical behavior. The XRD data confirmed the hexagonal wurtzite structure of pristine, Mn doped and Al, Mn co-doped ZnO. For morphological investigation SEM and TEM techniques were employed. The PL properties of the ZnO:Mn, Al sample revealed emission in the blue region (415-438 nm). Furthermore, IV studies were carried out to examine the conductivity of the ZnO:Mn, Al samples and maximum conductivity was found in the sample with 5% Al doping and annealing temperature 600 °C. The magnetic measurements revealed room temperature ferromagnetic behavior in the optimized ZnO:Mn, Al sample annealed at 600 °C which indicates its suitability for Magneto-Opto Electronic Applications.

Efficient luminomagnetic and conductive Eu and Dy doped ZnO phosphors for multifunctional devices

In this study, europium (Eu) and dysprosium-(Dy) doped phosphors, i.e., ZnO:Eu, ZnO:Dy, and Eu:Dy co-doped zinc oxide (ZnO:Eu, Dy) semiconductor phosphors, with optimized concentrations, were synthesized using the conventional solid-state reaction method in an oxygen environment. Detailed structural, morphological, and compositional investigations were conducted using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray measurements, respectively. Photoluminescence (PL) emission spectra were recorded under different excitation wavelengths to assess the optical characteristics. Electrical analysis was conducted using an inductance (L), capacitance (C), and resistance (R) (LCR) meter and a Keithley source meter, and magnetic analysis was performed using a vibrating sample magnetometer (VSM). XRD confirmed the presence of Eu and Dy ions because the diffraction peaks matched perfectly with those for Eu2O3 and Dy2O3, respectively. The PL results indicated the broad emissions from the samples in the visible region (400–700 nm) under different ultraviolet excitation wavelengths. The VSM results demonstrated that both the Dy-doped and Eu:Dy co-doped ZnO samples exhibited paramagnetic behavior at room temperature, but not the undoped and Eu-doped ZnO samples. The ZnO:Dy sample had superior parameters in terms of the electrical measurements such as the AC/DC conductivity, capacitance, current density, and dielectric constant compared with the ZnO:Eu and ZnO:Eu, Dy samples. These detailed investigations of the optical, magnetic, and electrical properties demonstrate that ZnO:Dy and ZnO:Eu, Dy may be promising materials for use in optical devices.