The dielectric behaviour of single-crystal MgO,Fe/MgO and Cr/MgO

The dielectric constants and loss factors,, for pure single-crystal MgO and for Fe-and Cr-doped crystals have been measured at frequencies, , from 500 Hz to 500 kHz at room temperature. For pure MgO at 1 kHz the values of and the loss tangent, tan , (9.62 and 2.16×10^–3, respectively) agree well with the data of Von Hippel; the conductivity, , varies as ⁿ withn=0.98±0.02. In Fe-doped crystals increases with Fe-concentration (at any given frequency); for a crystal doped with 12800 ppm Fe, was about four times the value for pure MgO. At all concentrations the variation of log with log was linear andn=0.98±0.02. A decrease in with increasing Fe-concentration was also observed. A similar, although less pronounced, behaviour was found in Cr-doped crystals. The effects are discussed in terms of hopping mechanisms.     

High frequency dielectric properties of MgO,Fe/MgO and Cr/MgO

The study of the dielectric constant and loss in pure single-crystal MgO and in Fe- and Cr-doped crystals, the low frequency results of which have been reported [1], has now been extended to cover frequencies from 500 Hz to 9 GHz. Measurements were made on the same specimens, at room temperature, using bridge, cavity, slotted-line and cavity-resonator techniques. Over the whole frequency range, a good fit is obtained to the Universal Laws of dielectric response: _ac ⁿ and (–) ^n–1 with n=0.98±0.02 for both pure and doped MgO. At any point in this frequency range the addition of iron or chromium increases and decreases , the changes being more pronounced with iron. These effects are discussed in terms of hopping mechanisms.     

Effect of Composition on the Structure and Properties of MgO/Y2O3 Composite Ceramics

Inorganic Materials - We have studied the effect of the ratio of the macrocomponents of magnesium oxide- and yttrium oxide-based composite ceramics on their microstructure and optical and...     

Substrate Biasing Effect during MgO Deposition in CoFeB/MgO/CoFeB MTJs

High tunneling magnetoresistance (TMR) ratio and low RA in magnetic tunnel junctions are necessary condition for application in magnetic random access memory. To get high TMR ratio and low RA, good quality of MgO (002) insulating layer is important. To increase crystalline quality of MgO (002) layer, we applied negative bias on the substrate during MgO deposition. We report the results of the tunneling magnetoresistance (TMR) ratio and the resistance-area product (RA) for CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with substrate bias voltage, and showed TMR increase and RA decrease with substrate bias. The effects of substrate bias voltage on the TMR ratio, RA and MgO (002) peak intensity are discussed.      

Creep of CaO/MgO refractories

The creep properties of a standard doloma brick (containing 40% MgO) and a magnesia-enriched doloma product (containing 60% MgO) have been compared with the behaviour of CaO-MgO samples having compositions and microstructures similar to those of the pellet raw materials used for manufacture of the fired doloma refractories. The creep strength is shown to be improved not only by magnesia enrichment but also by reducing the impurity levels, particularly the Fe₂O₃ content.     

纳米MgO/LDPE及SiO2/LDPE复合介质潮气吸附机制及其对直流电导特性的影响

为了研究纳米复合介质的吸潮特性及其对介电性能的影响,应用Materials Studio仿真分析MgO及SiO₂纳米粉末对水分子的吸附能,探讨了相关的吸潮机制及纳米MgO和纳米SiO₂粉末的吸潮特性,对吸潮前后MgO/低密度聚乙烯（LDPE）和SiO₂/LDPE复合介质介电性能的变化进行了试验研究。研究结果表明,水分子在氧化物表面的吸附点位主要是O原子,由于纳米SiO₂属无定形,水分子可渗入SiO₂纳米粒子内部与更多的O原子形成吸附作用,纳米SiO₂具有更大的吸潮量。由于纳米MgO对水分子的吸附能大于纳米SiO₂对水分子的吸附能,水分子更难被移除。纳米MgO/LDPE和纳米SiO₂/LDPE复合介质较LDPE更易吸潮,其原因是纳米粒子吸附水分子能力较强所致。吸潮对MgO/LDPE和纳米SiO₂/LDPE复合介质的介电性能有较大影响,吸潮后复合介质的电流密度值明显上升,水分子的存在可能破坏了原有界面区的紧密结构和荷电特性,削弱了复合介质对载流子迁移的抑制能力。当测试温度增加至60℃以上,受潮后复合介质吸附的水分子基本被移除,纳米MgO/LDPE和SiO₂/LDPE复合介质的电流密度值恢复到同干燥试样的电流密度值基本一致。     

Development of ZTO/Ag/ZTO transparent electrodes for thin film solar cells

Journal of Materials Science: Materials in Electronics - This article presents the optimization of Zinc Tin Oxide/Silver/Zinc Tin Oxide (ZTO/Ag/ZTO) multilayers to implement them in thin film solar...     

Effect of illumination on electrical characteristics of Au/Mn-complex/n-Si photodiode structures

Journal of Materials Science: Materials in Electronics - We were produced a various Mn-doped complex and presented it in Au/Mn-complex/n-Si structure as an interfacial layer. For this aim, a...     

Fabrication of Al/MgO/C and C/MgO/InSe/C tunneling barriers for tunable negative resistance and negative capacitance applications

In this work, the design and characterization of magnesium oxide based tunneling diodes which are produced on Al and InSe films as rectifying substrates are investigated. It was found that when Al thin films are used, the device exhibit tunneling diode behavior of sharp valley at 0.15 V and peak to valley current ratio (PVCR) of 11.4. In addition, the capacitance spectra of the Al/MgO/C device show a resonance peak of negative capacitance (NC) values at 44.7 MHz. The capacitance and resistance–voltage characteristics handled at an ac signal frequency of 100 MHz reflected a build in voltage (V_bi) of 1.29 V and a negative resistance (NR) effect above 2.05 V. This device quality factor (Q)–voltage response is ~10⁴. When the Al substrate is replaced by InSe thin film, the tunneling diode valley appeared at 1.1 V. In addition, the PVCR, NR range, NC resonance peak, Q and V_bi are found to be 135, 0.94–2.24 and 39.0 MHz, ~10⁵ and 1.34 V, respectively. Due to the wide differential negative resistance and capacitance voltage ranges and due to the response of the C/MgO/InSe/C device at 1.0 GHz, these devices appear to be suitable for applications as frequency mixers, amplifiers, and monostable–bistable circuit elements (MOBILE).     

Fabrication of ZnO/ZnS/ZnSe nanosheets for enhanced photocatalytic activity under simulated solar light

Journal of Materials Science: Materials in Electronics - Ternary composite ZnO/ZnS/ZnSe nanosheets (NSs) with diverse proportions of three modules successfully manufactured by a plain two-step...     

Influence of Diffused Boron Into MgO Barrier on Pinhole Creation in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

A relationship between boron (B) diffusion into the MgO barrier and pinhole creation in CoFeB/MgO/CoFeB-magnetic tunnel junctions (MTJs) was investigated. The diffused B in the MgO layer was identified by secondary ion mass spectrometry for the MTJs annealed at 350degC , which provide the giant magnetoresistance (TMR) ratio. The pinhole density, estimated from the statistic distribution of breakdown voltage of the TMR properties, increased as either the thickness or the B content of the CoFeB layer became thicker or higher. These experimental findings imply that the diffused B into the MgO barrier creates pinholes to short-circuit the tunnel conduction, since the amount of diffused B into the MgO barrier might be related to the total amount of the B content in the CoFeB layer. Three different techniques were found to be useful for the reduction of diffused B into the MgO barrier layer; usage of materials having boron affinity for capping layer, decrease of the total amount of B-content in CoFeB layer, and reduction of grain boundaries in the MgO barrier layer.     

Effects of MgO and MgO/Pd seed-layers on perpendicular magnetic anisotropy of CoPd thin films

We studied the effects of MgO and MgO/Pd seed-layers on perpendicular magnetic anisotropy in co-sputtered CoPd films. CoPd films with the MgO seed-layer showed perpendicular magnetic properties that were superior to those with another after annealing. The loop squareness was unity, indicating strong perpendicular magnetic anisotropy, when the MgO seed-layer was thicker than 2 nm. We observed that the out-of-plane CoPd (111) texture was strongly developed, as well as the in-plane tensile stress in the CoPd films. The magnetoelastic anisotropy coming from a negative magnetostriction λ₁₁₁ under the in-plane tensile stress dominating over other anisotropies is likely responsible for creating such strong perpendicular magnetic anisotropy. In the case of the MgO/Pd seed-layer, the CoPd films showed mixed anisotropy having both in-plane and out-of-plane magnetic anisotropy components after annealing. The appearance of the strong (100) texture of the CoPd films with the MgO/Pd seed-layer is believed to have caused the decrease in the perpendicular magnetic anisotropy that originated from the magnetoelastic anisotropy due to the additional contribution from the positive magnetostriction λ₁₀₀ but less contribution from the negative magnetostriction λ₁₁₁ when the CoPd films are under in-plane tensile stress.     

Interfacial interaction in Fe/MgO/Fe magnetic tunneling junctions

We present a study on interfacial structures and tunneling magnetoresistance (TMR) in Fe/MgO/Fe junctions using a MgO(111) film with {100} facets. It is shown using X-ray photoelectron spectroscopy that a FeO layer occurs at MgO/Fe rather than Fe/MgO interface, which could be used to tune the TMR effect. At the Fe/MgO interface, such a change in electronic structure is attributed to the band bending associated with a change in thickness of Fe films. The present study provides a new understanding on the Fe/MgO/Fe interfacial behavior and metal/oxide barriers involving electron transport.     

Multifunctional WSe2/SnSe2/WSe2 van der Waals heterostructures

Journal of Materials Science: Materials in Electronics - In this study, we report the fabrication of WSe2/SnSe2/WSe2 van der Waals (vdW) heterostructures for potential applications as tunnel...     

Combustion synthesis and dielectric properties of B4C/Al2O3/CNTs composite powders

Journal of Materials Science: Materials in Electronics - To develop a novel high-temperature microwave absorber, B4C/Al2O3/CNTs composite powders were prepared by a combustion synthesis method. The...     

Shape-dependent catalytic activity of CuO/MgO nanocatalysts

CuO/MgO catalysts with various shapes have been obtained by using morphology-controlled synthesis technology. It is demonstrated that there is a remarkable difference in catalytic activity for CO oxidation among these samples. However, when all these catalysts react with water before calcination, their shapes become irregular and similar, consequently, the difference of their catalytic activities disappears.     

Epitaxial growth of MgO/TiN multilayers on Cu

The growth of epitaxial MgO/TiN multilayer films on (001) Cu has been investigated. In particular, epitaxial structures were grown on (001) Cu layers that were epitaxial on (001) SrTiO₃. X-ray diffraction and reflection high-energy electron diffraction indicate that the multilayer structures are epitaxial on the (001) Cu surface. The motivation is the use of crystalline MgO/TiN multilayers as a diffusion barrier to both copper and oxygen. MgO/TiN multilayers are potentially useful as diffusion barriers for Cu interconnects on semiconductors as well as for superconducting wires based on the epitaxial growth of cuprate superconductors on biaxially textured copper.     

Fabrication of magnetic ZnO/ZnFe2O4/diatomite composites: improved photocatalytic efficiency under visible light irradiation

Journal of Materials Science: Materials in Electronics - The magnetic recoverable ZnO/ZnFe2O4/diatomite (ZZFDT) composite was synthesized by hydrothermal-precipitation method. The structure,...     

Preparation of SiOx–TiO2/Si/CNTs composite microspheres as novel anodes for lithium-ion battery with good cycle stability

Journal of Materials Science: Materials in Electronics - Si/carbon and SiOx/carbon composites have been widely studied to meet the increasing demand for high-energy-density lithium-ion batteries....     

Preparation and performance enhancement study of organic ZnO/Au/PEDOT:PSS heterojunction UV photodetector

Journal of Materials Science: Materials in Electronics - Organic/inorganic hybrid material properties and their interfaces are essential to obtain excellent device performance. In this paper, an...