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![a and b Read head sensor of hard disk drives (HDDs) and c The MgO tunnel barrier in magnetic tunneling junctions (MTJs) structure
(Reproduced with permission from Refs. [15, 16])](publication/331387939/figure/fig1/AS:941649211449370@1601518075514/a-and-b-Read-head-sensor-of-hard-disk-drives-HDDs-and-c-The-MgO-tunnel-barrier-in.png)
a and b Read head sensor of hard disk drives (HDDs) and c The MgO tunnel barrier in magnetic tunneling junctions (MTJs) structure (Reproduced with permission from Refs. [15, 16])
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The reaction between the water and the MgO thin film of the magnetic tunneling junction barrier under different temperatures were investigated. The epitaxial MgO (001) thin film with a thickness of 20 nm was exposed to the deionized water for 5 min at different water temperatures. X-ray photoelectron spectroscopy (XPS) combination with in situ Ar⁺...
Citations
... In order to understand heavy metal of SOC on ferromagnetic layer, the insulating layer or dielectric layer has inserted as intermediate layer to heavy metal and ferromagnetic layer. The insulation materials Al 2 O 3 , HfO 2 , and MgO [18][19][20][21][22] have been employed for multilayer stack. Especially, Al 2 O 3 is a material with good insulation and dielectric property [23][24][25][26][27][28] which has been often used as the magnetic tunneling junctions, and spin valve structure for read and write, and other spintronic applications. ...
This article shows low damping patterned FeGaB and Al2O3/FeGaB thin films. FeGaB has a lower damping factor (0.0071) than the Al2O3/FeGaB thin film. The coercive field and magnetic anisotropy of Al2O3/FeGaB thin films are enhanced as a result of static magnetization (Magneto-Optical Kerr Effect). The magnetic anisotropy of the Al2O3/FeGaB film produces a larger magnetic domain evolution at 10.2 Oe than the FeGaB thin film. The magnetic domain wall velocity for the FeGaB thin film is shown to be larger utilizing micromagnetic modeling due to its low anisotropy and the impact of spin–orbit coupling. As a result of our findings, it can be employed in microwave and spintronic applications.
... However, when exposed to the air, MgO could react with water contained into the ambient atmosphere, resulting in lower performance as tunnel barrier for spintronics. 47 As we aim to use this ultrathin layer as a functional tunnel barrier, we develop a further processing step where we focus on a combined protection−encapsulation barrier stack as shown in Figure 2 where we protect it with an additional Al 2 O 3 layer that will be locally removed only in the last step of the device fabrication process. This will allow to protect MgO high quality over time and obtain its best performance for spintronics applications. ...
... The MgO barrier is grown under the same conditions as previously described, but additionally, to prevent its degradation by moisture, 47 we further developed a removable Al 2 O 3 encapsulation scheme. After MgO growth, the ALD chamber is heated to 300°C. ...
2D materials have recently demonstrated a strong potential for spintronic applications. This has been further reinforced by the discovery of ferromagnetic 2D layers. Nevertheless, the fragility of many 2D magnetic materials to ambient conditions has so far hindered their faster characterization and integration into devices. We report here on a simple large-scale method that allows to stabilize strongly air sensitive materials, such as CrBr3, down to the monolayer limit with ultrathin barriers grown by atomic layer deposition (ALD). We focus on MgO as a passivation layer to additionally serve as tunnel spin injection barrier for spintronic applications. We develop a special removable combined protection-encapsulation stack to better preserve 2D material and MgO barrier qualities during device fabrication. This scheme allows to observe 2D ferromagnet stability over one year of air exposure and to demonstrate CrBr3 successful integration into vertical devices. Overall, these results highlight an efficient way to handle these materials in ambient conditions, unlocking possibilities to fasten their advanced characterization and ease their integration into devices.
... This shows that the MgO adhesion layer creates a high enough mechanical stability for the nanostructures to survive the fabrication process. It should be noted that the affinity of MgO to water is known 27 . However, in a plasmonic device where MgO adhesion layer coated by noble metals or any other stable material water exposure and potential damages will be minimized. ...
The magnesium oxide (MgO) adhesion layer is proposed to avoid adverse effects of lossy metallic adhesion layers in thin film plasmonic nanostructures. Such adverse effects can be in the form of resonance broadening and a decrease in the resonance magnitude. We fabricate and test the quality of MgO adhesion layers and determine its optical properties through ellipsometry measurements. We also provide the plasmonic response of various plasmonic nanostructures (nanohole array, nanodisk array, dimer nanohole array, and bowtie slot antenna array) with a MgO adhesion layer and conventional adhesion layers including titanium (Ti), chromium (Cr), tantalum (Ta), and indium tin oxide (ITO). Our results show that unlike conventional adhesives, MgO has almost no adverse effect on the plasmonic resonance of the designed nanostructures.
... Recently, study of the physicochemical properties of magnesium oxide (MgO) has attracted the interest of many scientists due to its extensive application in different technological fields including optoelectronics, magneto-optics, solar cells, sensors, anti-reflective coating and toxic waste remediation [1][2][3][4]. These studies opened the door to investigate the correlation between various properties of nanocrystalline magnesium oxide (i.e., morphological, optical, magnetic, and electrical) and its potential application in more detail [5,6]. LD MgO nanostructures are widely used in water purification processes as a highly efficient catalyst due to the high surface to volume ratio with presence of oxygen/metal vacancies, which in turn facilitate charge separations on MgO surface [7]. ...
In this study, low-dimensional (LD) MgO nanostructured thin films with three different morphologies, namely, nanowires (NWs), nanotubes (NTs) and nanoparticles (NPs) were fabricated by a vapor transport method on quartz and silicon substrates under optimum growth conditions. It was found that the deposition parameters have great influences on the morphology, optical, photoluminescent, electrical, gas sensing and magnetic behavior of the resulting products. X-ray diffraction analysis illustrated that all three LD MgO nanostructures have five expected Bragg peaks of cubic MgO phase purity with well crystalline nature. The morphology and diameter of LD MgO nanostructures were probed by scanning electron and transmission electron-microscopes. The optical band gap values for LD MgO nanostructure films varies between 3.65 eV and 3.95 eV depending on growth conditions. It was found that all MgO films exhibit two distinguishing PL peaks related to the near band edge luminescence of LD MgO nanostructures and defect levels produced by oxygen vacancies, respectively. It was found that the dependence of electrical conductivity on film morphology can be attributed to the defect levels produced by O⁻² ion vacancies during the synthesis process. NH3 gas sensing efficiency of LD MgO nanostructures with various morphologies were carried out at different operating temperatures from 25 °C to 300 °C. The MgO film with NWs structure has the highest sensor response value of 27 at 100 °C and the film with NPs structure has the lowest response value of 12 at 150 °C. Ferromagnetic order has been recorded for all morphologies at room temperature with clear hysteresis loop and different magnetic parameters depending on growth conditions. Thus, our results present a direct route for the growth of high-quality and diverse LD MgO nanostructures developed via vapor transport for many technological applications.
X-ray photoelectron spectroscopy depth profiling combined with ion beam etching methods is a primary tool to study the chemical composition of functional materials at different scales from the surface to the bulk.
This paper focuses on magnesium oxide and hydroxide, which are compounds with favorable and exclusive features for various applications. Magnesium oxide nanoparticles (MgO NPs) have been reportedly produced through green synthesis procedures. Natural materials or their products including plants extracts or those of plants parts, roots, fruits, and gums have been used as reducing and capping agents in the synthesis procedures. MgO nanostructures have been reportedly used in drug delivery, anti-cancer and anti-bacterial applications, which has increased the risks of human exposure to these materials. A full understanding of the influence of MgO NPs and the underlying mechanisms of their actions are important in evaluating the environmental risks of using these nanoparticles. MgO NPs are known to enjoy high biocompatibility and stability, and low IC50 values in comparison with copper, manganese, tin, cobalt, manganese oxide nanoparticles. This has been attributed to the great bioavailability, and lower toxicity (hemolytic investigations) of these particles. MgO NPs are also known as effective chemotherapeutic and bacteriostatic agents for use in the fast detection and diagnosis of various cancers. However, more studies should be aimed at evaluating the toxic effects of MgO NPs on individual organism. As a first step, this review attempts to shed some light on the advancements in the area of green synthesis for preparing efficient NPs including MgO for future applications.
Transition metal oxides and transition metal containing oxides have been extensively researched in heterogeneous catalytic ozonation for water treatment. However, catalytic mechanism for typical transition metal oxide – manganese oxide (MnO2) in catalytic ozonation is still ambiguous. Herein, MnO2 and magnesium manganese oxides (MgMnxOy) with different molar ratios of Mg to Mn were analysed by linear sweep voltammetry (LSV) test to explore a necessary condition for electron transfer reaction between ozone and acid sites of the catalysts in aqueous solution. And their catalytic performances were investigated in ozonation of acetic acid aqueous solution at a neutral pH. It is found that electron transfer reaction occurs in manganese containing oxides catalytic ozonation when ozone is adsorbed on protonated surface hydroxyl groups of acid sites (Mn²⁺/Mn³⁺ in the lattice). But ozone that is absorbed on protonated hydroxyl groups of Mg²⁺ in the lattice cannot react with acid sites to generate reactive oxygen species in MgMnxOy catalytic ozonation. Protonation of hydroxyl groups on acid sites can be achieved by enhancement in point of zero charge (pHPZC) of the catalysts or decrease in initial pH of aqueous solution. Protonation ability of hydroxyl groups on acid sites and electron transfer ability of acid sites are positively related to Mg content in MgMnxOy. MgMnxOy with 2:1 molar ratio of Mg to Mn (Mg2MnOy) exhibits the highest catalytic activity and good stability in ozonation of acetic acid. On basis of catalytic mechanism on acid sites of manganese containing oxides, modification and application of manganese containing oxides would be further developed in heterogeneous catalytic ozonation for water treatment.
The degradation of the MgO thin film barrier of magnetic tunneling junctions caused by the dissolution of the film in deionized water during manufacturing processes is critical to the performance of spintronic devices. In this work, the influence of gas atmospheres including oxygen (O2), nitrogen (N2) and carbon dioxide (CO2) on dissolution behavior of the film was investigated by using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic absorption spectroscopy (AAS). XPS depth profile results reveal that deionized water reacts with the film and infiltrates into the deeper layer of the film resulting in the chemical transformation of MgO to Mg(OH)2. AAS results confirm that the films dissolve because Mg²⁺ ions are released into deionized water. Consequently, Mg concentration in deionized water increases. It is found that the concentration of Mg²⁺ ions in deionized water is highest in the dissolution of CO2-saturated deionized water and lowest in those of N2-saturated deionized water. Simultaneously, the release of Mg²⁺ causes the development of the coral-like clusters over their surface and a decrease of the film thickness. XPS depth profile and SEM cross-sectional results demonstrate that the film thickness slightly decreases in sample N2 and decreases considerably in sample CO2. This is due to the fact that CO2 gas reacts with water, reducing its pH and thus increasing of the dissolution rate, while N2 gas has no reaction with water. Finally, this work proposes a qualitative model based on chemical reaction to explain the dissolution behavior of the film.
In this work, magnesium oxide was elaborated on a glass substrate at 450°C by a pneumatic spray technique. The structural, optical, and electrical properties were studied at different MgO concentrations (.05, .10, .15, and .2 mol L ⁻¹ ). Poly-crystalline MgO films with a cubic structure with a strong (002) preferred orientation were observed at all sprayed films, with a maximum crystallite size of 21.4 nm attained by the sprayed film at .2 mol L ⁻¹ . Good transmission was found in the deposited MgO thin films with lowest molarity. The transmission of MgO thin films decreases rapidly as the wavelength increases in the range of 300–400 nm and then increases slowly at higher wavelengths. The bandgap of MgO thin films decreases as the molarity increases, and the band gap values range between 4.8 and 4.3 eV. The Urbach energy values range between 375 and 519 meV. The electrical resistance of our films is on the order of 2 × 10 ⁷ Ω. The prepared MgO thin films were suitable for electronic packaging; they are capable to provide very stable and high secondary electron emission combined with low bandgap energy and low electrical resistance.
