Deposition Of MgO Research Articles

Collagen membrane functionalized with magnesium oxide via room-temperature atomic layer deposition promotes osteopromotive and antimicrobial properties.

Artificial bone grafting materials such as collagen are gaining interest due to the ease of production and implantation. However, collagen must be supplemented with additional coating materials for improved osteointegration. Here, we report room-temperature atomic layer deposition (ALD) of MgO, a novel method to coat collagen membranes with MgO. Characterization techniques such as X-ray photoelectron spectroscopy, Raman spectroscopy, and electron beam dispersion mapping confirm the chemical nature of the film. Scanning electron and atomic force microscopies show the surface topography and morphology of the collagen fibers were not altered during the ALD of MgO. Slow release of magnesium ions promotes bone growth, and we show the deposited MgO film leaches trace amounts of Mg when incubated in phosphate-buffered saline at 37°C. The coated collagen membrane had a superhydrophilic surface immediately after the deposition of MgO. The film was not toxic to human cells and demonstrated antibacterial properties against bacterial biofilms. Furthermore, in vivo studies performed on calvaria rats showed MgO-coated membranes (200 and 500 ALD) elicit a higher inflammatory response, leading to an increase in angiogenesis and a greater bone formation, mainly for Col-MgO500, compared to uncoated collagen. Based on the characterization of the MgO film and in vitro and in vivo data, the MgO-coated collagen membranes are excellent candidates for guided bone regeneration.

Removal behavior of Al–Ti–O inclusions in aluminum deoxidized molten steel containing titanium by microporous magnesium foam ceramic filters

Al–Ti–O inclusions in aluminum deoxidized and titanium (Ti)-alloyed steel aggravate the submerged nozzle clogging and instability of the continuous casting process, lowering the cleanliness of casting billet. In the present investigation, the removal behavior of the oxide inclusions in aluminum deoxidized IF steel and Ti-alloyed welding wire steel by microporous/fused MgO foam ceramic filter (PMF/FMF) and the improvement of the steel cleanliness were comparatively investigated. It is found that MgO foam ceramic filters immersed in Al deoxidized steel effectively reduced its number density of Al2O3 inclusions and total oxygen (TO) content, by use of forming Al–Mg–O spinel interface reaction layer between the filters and tested steel. Furthermore, the cleanliness increase of Ti-alloyed steel immersed by the filters, due to formation of a more complete and continuous Al–Mg–Ti–O spinel layer on their surface, was bigger compared with that in Ti-free steel, with sporadically distributed Al–Mg–O spinel of interface layer on the surface of filters immersed in Ti-free steel. This is ascribed to the higher Ti content and some liquid inclusion of MgO–Al2O3-TiOX in Ti-alloyed steel, enhancing the reaction of the MgO of aggregates in the filters with Al, Ti, and O and deposition of other solid MgO–Al2O3-TiOX on the surface of the filter, respectively. In addition, the better purification efficiency of the PMF on tested steel compared with the FMF, was due to its higher porosity, roughness and more liquid phase components of the matrix in PMF, which improve the reaction of filter with liquid steel, and raise its adsorption capacity with Al2O3-based inclusions in the steel, forming Al–Mg–O spinel interface layer to removal the oxide inclusions.

Transpiration effect on Falkner-Skan bioconvective mixed nanoliquid flow above a poignant wedge

Numerical computations are executed to investigate the consequence of the Buongiorno slip mechanism and radiative heat on gyrotactic microorganisms containing Casson cross nanoliquid flow across a moving wedge. The mixed nanofluid comprises magnesium and copper oxide (MgO and CuO) nanoparticles pondered in water. The bioconvection Falkner-Skan flow governing equations are resolved using the BVP5C Matlab package. Simultaneous solutions are drawn for suction and injection cases. Plots illustrate the effect of pertinent physical factors on flow, thermal, diffusion, and motile organism density. The wall friction, energy rate, and mass transmission are interpreted via tables. The outcomes reveal that the consequence of embedded features on the bioconvective mixed nanoliquid stream are substantial in the suction case as matched with injection case. The deposition of MgO and CuO nanomaterials raises the heat transmission of the base liquid to a more significant level. Further, the Buongiorno slip mechanism parameter intensifies the thermal outlines and decays the energy transport rate for suction/injection cases. The major applications of current investigation can be found in geothermal energy systems.

Co - Fe - B/MgO/Ge Spin Photodiode Operating at Telecommunication Wavelength with Zero Applied Magnetic Field

We report on the growth and study of Co-Fe-B/MgO/Ge(001) spin photodiode by using a combination of both molecular beam epitaxy (MBE) and sputtering methods. An epitaxial growth of MgO on Ge in MBE is achieved by the deposition of MgO at room temperature (RT) followed by a post-growth anneal-ing at 300 °C. The spin detector, which consists of 1.1-nm ultrathin Co-Fe-B layer capped with 5-nm Ta is subsequently grown by sputtering at RT. After a post-growth annealing of the whole structure at 250 °C, we obtain clear evidence of a strong perpendicular magnetic anisotropy in the temperature range 10-300 K. Co-Fe-B/MgO/Ge(001) heterojunctions are then processed into spin photodiodes demonstrating at zero magnetic field a photocurrent helicity asymmetry of about 0.9% at 9 K and 0.1% at RT at the telecommunication wavelength of 1310 nm. The demonstration of a spin photodiode working at a telecommunication wavelength with zero applied magnetic field is of great interest for future applications of the optical transport of spin information.

Interlayer-assisted atomic layer deposition of MgO as a magnetic tunneling junction insulators

The growth behavior of MgO deposited on a Mg interlayer by plasma-enhanced atomic layer deposition (PE-ALD) was investigated to improve the MgO layer quality for magnetic tunneling junction (MTJ) applications. The Mg interlayer was inserted beneath the PE-ALD MgO film to prevent the oxidation of the bottom substrate layer. The chemical bonding status, elemental depth profile, and electron microscopy results for the PE-ALD Mg/MgO stack indicate that the Mg interlayer successfully blocked the oxidation of the substrate via its transformation to MgO. In addition, a change of the preferred orientation from (111) to (200) was observed in the X-ray diffraction pattern when the Mg interlayer was applied. This was attributed to the (200)-preferred orientation of the MgO formed through the oxidation of the Mg interlayer. The use of Mg interlayer is aim to prevent the degradation of the tunneling magneto-resistance properties by not only protecting the bottom layer (i.e., = CoFeB film in MTJs) from oxidation but also changing the preferred orientation from (111) to (200).

Relative strength of perpendicular magnetic anisotropy at bottom and top interfaces in Pt/Co/MgO trilayers

In Pt/Co/MgO trilayers, the contribution to the total perpendicular magnetic anisotropy from the bottom Pt/Co interface is significantly greater than that from the top Co/MgO interface at intermediate annealing temperatures. However, the relative contribution is reversed at the highest annealing temperature examined in this study, 400 °C. These results indicate that as the annealing temperature increases, the quality of the Pt/Co interface deteriorates owing to the intermixing of Pt and Co, whereas the quality of the Co/MgO interface improves as oxygen atoms, which are interpenetrated into the Co layer during the deposition of MgO, are diffused toward the Co/MgO interface.

Formation mechanism of dense anti-oxidation layer in Al-Si-MgO composites sintered in air condition

An Al-Si-MgO composite was prepared at 1450°C for 2h in air using aluminium powder, silicon powder and magnesia powder as raw materials. The calcined composite was characterized and analyzed by XRD, SEM and EDS. The results show that after being calcined, Al and Si in the composite reacted to form MgAl2O4 and Mg2SiO4 respectively, rather than the low melting point phase located within the MgO-Al2O3-SiO2 system. At high temperature, Al2O (g) and Mg (g) can be formed and spread along the pores in the specimen owing to the inhomogeneous gas concentration, and then oxidized by O2 (g). Owing to the deposition of Al2O3 and MgO and the volume expansion caused by Si transformation into SiO2, a dense layer containing MgO, MgAl2O4 and Mg2SiO4 finally forms close to the surface of Al-Si-MgO composite. The formation of the dense layer improves the antioxidant properties of the composite, forms a plate-like AlN polytype and leads to the retention of the unreacted Si in the centre of Al-Si-MgO composite. In addition, the formation mechanism for the dense layer in the Al-Si-MgO composite was also established in this work.

Para-selective methylation of toluene with methanol over nano-sized ZSM-5 catalysts: Synergistic effects of surface modifications with SiO2, P2O5 and MgO

The nano-sized ZSM-5 catalysts were modified by surface coating with SiO2, P2O5, MgO and their combinations; the catalytic properties were investigated in the shape-selective methylation of toluene with methanol. The catalysts were characterized by XRD, XRF, N2 adsorption–desorption, temperature programmed desorption of ammonia (NH3-TPD), Fourier-transform infrared spectra of adsorbed pyridine/2,6-di-tert-butylpyridine, and adsorption of n-hexane/cyclohexane. The passivation of Lewis acid sites occurs prior to that of the Brönsted acid sites over ZSM-5 modified by SiO2, while P2O5 or MgO preferentially neutralizes the Brönsted acid sites of ZSM-5. The deposition of MgO is more efficient in passivating the acid sites and narrowing the pore openings, compared to SiO2 or P2O5 modification with the same oxide content (<9wt%). The single modification could not completely passivate the external surface acid sites and simultaneously narrow the pore openings to a proper extent; so the selectivity to para-xylene does not exceed 90% even at the highest oxide loading. The multiple modification by SiO2, P2O5 and MgO, with a suitable sequence can efficiently eliminate external surface acid sites, and simultaneously narrow the pore openings, which led to a higher para-selectivity (∼98%). The combined modification with SiO2, P2O5 and MgO in a proper sequence can lead to a synergistic effect for tailoring the acid property and pore mouth of the catalyst, thus enhancing the para-selectivity to ∼98% and improving catalytic stability, as demonstrated by flow test for 1000h on stream.

Oxidation states and quality of upper interfaces in magnetic tunnel junctions: oxygen effect on crystallization of interfaces

In this study, we have deposited an 57Fe sensor layer at the upper interface, i.e. the interface between the oxide barrier and the upper electrode in selected magnetic tunnel junctions (MTJs), in order to perform nuclear resonant scattering with the aim of obtaining direct information on the magnetic properties and quality of this interface. This is a unique approach as it makes use of this powerful technique to give information at the atomic level, and specifically from the interface where the sensor layer is deposited. By varying sample tunnel barrier thicknesses and oxidation times in the preparation of this barrier, we have observed that longer oxidation time results in not only an increase of the magnetic hyperfine fields, but also causes an interesting crystallization and smoothing of the interface. We also observed that boron atoms diffuse away from the lower part of the upper FeCoB electrode toward the capping layer. An important observation, which has a crucial effect in tunnel magnetoresistance values, is the absence of any magnetically dead FeO layer at the interface. Another finding is that the deposition of Fe on MgO is much smoother than the deposition of MgO on Fe.

Investigation of atomic layer deposition of magnesium oxide on a CoFeB layer for three-dimensional magnetic tunneling junctions

In this study, we comparatively investigated thermal- and plasma-enhanced atomic layer deposition (Th- and PE-ALD) of MgO on a CoFeB layer. MgCp2 (Bis(cyclopentadienyl)magnesium) was used as a Mg precursor and H2O and O2 plasma were employed as reactants for the Th- and PE-ALD process, respectively. Th- and PE-ALD MgO formed interlayer between MgO and CoFeB layer due to the oxidation of CoFeB by H2O and O2 plasma during the Th- and PE-ALD process. While interlayer formation was observed to be less than 1nm for Th-ALD MgO, the PE-ALD MgO process resulted in an approximately 5nm thick, predominantly FeOx oxidation of CoFeB. This was due to the high reactivity of the O radicals and the higher driving force of Fe for oxidation when compared with Co. Our results show that the Th-ALD MgO process has a better potential as a deposition technique to form tunnel barrier of magnetic tunneling junctions (MTJs).

Synchrotron radiation photoemission study of interface formation between MgO and the atomically clean In0.53Ga0.47As surface

AbstractThe evolution of interface formation between MgO and the atomically clean In0.53Ga0.47As is studied by synchrotron radiation based photoemission. The deposition of MgO in a step wise fashion on the decapped In0.53Ga0.47As surface at room temperature results in the growth of an ultrathin interfacial oxide layer. Subsequent thermal annealing at 400 °C led to the reduction of the As and In oxides and the appearance of a Ga oxide component. The deposition of metallic Mg resulted in the further removal of the interfacial oxide and the out diffusion of In into the overlayer indicating severe disruption of the interface. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Electrophoretically self-assembled mixed metal oxide-TiO2 nano-composite film structures for photoelectrochemical energy conversion: Probing of charge recombination and electron transport resistances

Nanotitania/metal oxide composite films are prepared via the coupling of low DC voltage Electrophoretic Deposition (EPD) of P25 TiO2 nanoparticles with simultaneous electrolytic deposition of hydrous metal oxides, namely ZnO, MgO and Al2O3. The nanocomposite films are built into dye-sensitized solar cell photoanodes and their interfacial charge recombination and electronic resistances are investigated. The nano hydrous oxides were found to co-deposit (1–3 wt%) uniformly within the TiO2 film (forming island-like nanodeposits) significantly increasing film adhesion. Analysis via Electrochemical Impedance Spectroscopy and Open Circuit Voltage Decay techniques found, among the three composite films, the TiO2–Al2O3 electrode to exhibit the highest charge recombination resistance at the TiO2/electrolyte interface (Rrec) and as consequence an increase in Voc. However, its conversion efficiency (4.14%) was the lowest because it suffered from very high electron transport resistance (Rt) in the TiO2 network. By comparison, the TiO2–MgO film resulted in 5.40% efficiency and the TiO2–ZnO film in 5.85% efficiency-both exhibiting significantly lower Rt resistance. The obtained results point to the need for simultaneous optimization of the nanocomposite TiO2/metal oxide film structure in terms of high interfacial charge recombination resistance and low overall electron transport resistance.

Ab initio atomistic thermodynamics calculations of the initial deposition of epitaxial MgO film on GaAs(001)-β2(2 × 4)

Ab initio calculations were performed to investigate the initial deposition of epitaxial MgO on GaAs(001)-β2(2 × 4). The differences between the chemical bonding of Mg-As and O-As were characterized by the adsorption energies of atomic O and Mg at several symmetrically distinct sites, and O bonding was substantially stronger than that of Mg. Thermodynamics were analyzed through the introduction of environmental chemical potentials simulating in situ growth conditions by the sputtering of a stoichiometric MgO target. A surface phase diagram was generated under Mg and O environments with constrained equilibrium, and the results explained the initial formation of an epitaxial MgO phase on GaAs(001)-β2(2 × 4).

Structural and Magnetic Studies on Iron Oxide and Iron-Magnesium Oxide Thin Films Deposited Using Ferrocene and (Dimethylaminomethyl)ferrocene Precursors

Iron oxide and magnesium-doped iron oxide films were grown by atomic layer deposition in the temperature range of 350–500°C from ferrocene, (dimethylaminomethyl)ferrocene, magnesium β-diketonate, and ozone. Phase composition of the films depended on the deposition temperature, as magnetite and/or maghemite tended to form instead of hematite upon lowering the temperature. Iron oxide layers were also mixed with magnesium oxide by alternate deposition of MgO and Fe2O3 which also favored the formation of magnetite or maghemite structure prior to hematite. Scanning electron microscopy implied the smoothening of the films after doping with magnesium oxide. Magnetometry was used to study the effects of temperature and doping levels on the magnetic properties of the films.

유도결합 플라즈마 스퍼터링 장치에서 MgO의 반응성 증착 시 공정 진단

Process analysis was carried out during deposition of MgO by inductively coupled plasma assisted reactive magnetron sputtering in Ar and <TEX>$O_2$</TEX> ambient. At the initiation of Mg sputtering with bipolar pulsed dc power in Ar ambient, total pressure showed sharp increase and then slow fall. To analyse partial pressure change, QMS was used in downstream region, where the total pressure was maintained as low as <TEX>$10^{-5}$</TEX> Torr during plasma processing, good for ion source and quadrupole operation. At base pressure, the major impurity was <TEX>$H_2O$</TEX> and the second major impurity was <TEX>$CO/N_2$</TEX> about 10%. During sputtering of Mg in Ar, <TEX>$H_2$</TEX> soared up to 10.7% of Ar and remained as the major impurity during all the later process time. When <TEX>$O_2$</TEX> was mixed with Ar, the partial pressure of Ar decreased in proportion to <TEX>$O_2$</TEX> flow rate and that of <TEX>$H_2$</TEX> dropped down to 2%. It was understood as Mg target surface was oxidized to stop <TEX>$H_2$</TEX> emission by Ar ion sputtering. With ICP turned on, the major impurity <TEX>$H_2$</TEX> was converted into <TEX>$H_2O$</TEX> consuming <TEX>$O_2$</TEX> and C was also oxidized to evolve CO and <TEX>$CO_2$</TEX>.

X-ray studies of interface Fe-oxide in annealed MgO based magnetic tunneling junctions

X-ray absorption spectroscopy and X-ray scattering have been used to determine the oxidation reactions at the buried MgO/Fe interface as a result of the deposition of MgO. We confirm that Fe-oxide is present at the MgO/Fe and MgO/CoFe interfaces and amounts to less than 1mL in thickness. The Fe-oxide is a mixture of different iron oxide phases within the ultra-thin layer which can be reduced following annealing. We observe the transformation of the interfacial oxide from a more Fe2O3-like phase to a more FeO-like phase following annealing, and that this process is most noticeable between the 200 and 350°C annealing steps. In addition, the formation of a more bulk like MgO electronic structure following annealing was observed.

YBCO Superconductor Wire based on IBAD-Textured Templates and RCE of YBCO: Process Economics

High-temperature superconductor wire based on the YBa2Cu3Oy compound offers unprecedented performance that stands well above any other superconductor in terms of temperature and magnetic field of operation. We discuss a cost estimate model for production of coated conductors based on ion-beam–assisted deposition (IBAD) of MgO and reactive co-evaporation (RCE) of YBCO. Our results indicate that cost of coated conductors can be below $10/kAm already at 5000 km production volume of 4-mm superconductor wire, with 500 A/cm and 2 μm of YBCO. The total Ic /width is a key parameter for cost/performance of the coated conductor.

The Role of Nucleation Surfaces in the Texture Development of Magnesium Oxide During Ion Beam Assisted Deposition

Both the structure and the type of the nucleation surface play a key role in texture development of IBAD MgO films. We have examined these features in Al2O3 and Y2O3 thin films using two different types of deposition methods, atomic layer deposition (ALD) and electron beam evaporation (EBE). Examination of EBE Al2O3 with in situ reflected high-energy electron diffraction (RHEED) films reveals the presence of a nanocrystalline structure that remains unchanged after and is insensitive to ion irradiation with 750 eV argon ions. In contrast, ALD Al2O3 examined with the same method reveals a featureless image that appears amorphous. Use of the ALD Al2O3 film can result in well-textured films with reasonable in-plane mosaic spread values (~ 14°) without process optimization. Similar results were obtained on ALD and EBE Y2O3 films, although, the EBE Y2O3 appeared amorphous in the RHEED even before exposure to the ion beam. The ALD Y2O3 film resulted in an in-plane texture of ~ 10°. Finally, bare silicon substrates were examined. It was found that even with the native oxide remaining on its surface, the silicon underneath was amorphized by the ion beam and provided a suitable surface for the deposition of biaxial textured MgO with an in-plane texture of ~ 7° FWHM.

The encapsulation of an organic light-emitting diode using organic–inorganic hybrid materials and MgO

The characteristics of organic–inorganic multi-barriers were investigated in this study. Polymerized cycloaliphatic epoxy hybrid materials (hybrimers), synthesized by a sol–gel method and MgO were used as an organic and inorganic material, respectively. We performed a Ca test at 30 °C and 90% R.H. A multi-barrier of 6 dyads on 100 μm thick PET resulted in a water vapor transmission rate (WVTR) of 4.9 × 10 −5 g/m 2 day and optical transmittance of 81.8% in the visible region (350–850 nm). We suggested relatively simple passivation method with a solution process involving an organic material coupled with low temperature deposition of MgO using an electron beam evaporator. Due to the solution process of the organic layer, the OLEDs were passivated without dark spots or an additional protective layer. After driving of 740 h with a constant current source under ambient conditions, a half-life time of 15,000 h was estimated by the stretched exponential decay (SED) model with an initial luminance value L 0 = 1000 cd/m 2.

Controlled synthesis and characterisation of MgOnanoparticles, thin films and polycrystalline nanorods derived from a Mg(ii) single source precursor

The new magnesium (II) based oximato complex tris(aquo)-bis[2-(methoxyimino)-propanoato]magnesium(II) (1) has been prepared and fully characterised. This oximato complex serves as an ideal molecular single source precursor for chemical solution deposition and formation of cubic nanoscaled MgO from which thin films (2D morphology) and 1D materials (MgO rods) are accessible. A first ceramisation process starts with formation of an amorphous phase and occurs already at 190 °C and is completed after full conversion of the pre-ceramic into crystalline cubic MgO at 450 °C. Highly uniform and smooth films of MgO which show a preferential (111) orientation of the crystallites could be obtained at 450 °C. The low decomposition temperature of the precursor also allows the use of polymer based track-etched polycarbonate membranes as templates for 1D MgO structures with predictable geometric parameters (length and diameter). In this way, so far rarely observed polycrystalline MgO nanorods could be synthesised and fully characterised.