Thick Aluminum Layer Research Articles

무기금속 다층박막을 적용한 유기발광소자의 제작 및 특성 분석에 관한 연구

IMML(Inorganic metal multi-layer) was used as cathode in the OLED devices to reduce the reflectance or ITO and increase the contrast ratio. Device structure was . and DCJTB (4 - (dicyanomethylene) - 2 - ( 1 - propyls) 6 - methy 4H - pyrans) as host material lot red emission and red emitting guest material. IMML made three different layer: thin aluminum layer, aluminum layer doped with silicon monoxide, thick aluminum layer. The red OLED device with IMML showed the average reflectance of , and then normal OLED with or without polarizer showed the average reflectance of , at visible range from 380 nm to 780 nm. The brightness of OLED with IMML at 13 V was 5557 , and that of normal OLED with polarizer was 4872 . IMML could be the substitution for polarizer with same reflection, low cost, easy process in flat panel display market.

The growth of protective ultra-thin alumina layers on γ-TiAl(1 1 1) intermetallic single-crystal surfaces

An XPS and AES study of the early stages of oxidation of γ-TiAl(1 1 1) surfaces at 650 °C under 1.0 × 10 −7–1.0 × 10 −6 mbar O 2 is reported. The data evidence a first regime of oxidation characterized by the growth of a pure alumina layer followed by a second regime of simultaneous oxidation of both alloying elements. In the first regime, continuous alumina layers from ∼0.4 to ∼1.5 nm thick have been observed by angle-resolved XPS. The composition of the metallic phase underneath the growing oxide is modified by a depletion of Al and the injection of Al vacancies in the metal during the growth of the transient alumina formed at 650 °C. The onset of Ti oxidation was repeatedly observed for a critical concentration in the modified region of the alloy underneath the alumina layer: Ti 75±2Al 25±2 (Ti 50Al 17±2V(Al) 33±2), showing that decreasing the number of Ti–Al bonds in the modified intermetallic region increases the activity of Ti up to a critical point where its oxidation at the oxide/metal interface becomes competitive with that of Al. The growth of Ti 3+ and Ti 4+ oxide particles observed above the alumina layer by angle-resolved XPS indicates the transport of titanium cations trough the alumina layer and their subsequent reaction with oxygen at the outer gas/oxide interface. Improving structural ordering in the intermetallic phase slows down the growth kinetics of the alumina layer and the related Al-depletion of the substrate, and increases the resistance of the alloy to the subsequent oxidation of Ti. This is assigned to two combined effects: a slower diffusion of Al in the better ordered metallic phase and the growth of less defective alumina layers allowing to slow down the ionic transport through the oxide. Highly stable and corrosion resistant alloy surfaces covered by a 0.4 nm thick alumina layer have been obtained by slowly oxidizing the alloy at lower partial pressure (<5.0 × 10 −10 mbar O 2).

Abnormal Grain Growth During Rapid Annealing of Sol–Gel Alumina Thin Film Deposited on Ni‐Based Superalloy

A ∼50 nm thick alumina layer was deposited on an Ni‐based superalloy substrate by a sol–gel method. α‐AlOOH particles presented in the layer after drying at 140°C transformed mostly to α‐Al2O3 grains within ∼1 min at 1100°C under a low oxygen partial pressure annealing environment. During the same time period, the α‐Al2O3 grains grew significantly in the lateral direction, resulting in the aspect ratio of grain diameter to thickness of ∼20. The presence of a preferred orientation in the α‐Al2O3 layer suggested that the mechanism for the lateral growth was abnormal. The lateral growth mechanism appeared to become very slow when a critical thickness (∼100 nm) was reached.

Strong light-matter coupling at room temperature in simple geometry GaN microcavities grown on silicon

The reflectance spectra of simple design GaN-based microcavities have been studied in the 5 K–300 K range. The epitaxial structure consists of the silicon substrate and the stack of buffer layers as the back mirror, a GaN active layer, and a 100 Å thick aluminium layer as the top mirror. Active layer thicknesses of λ∕2, λ, or 3λ∕2 were investigated. The samples with GaN thicknesses λ∕2 and λ display an anticrossing behavior between the cavity and exciton modes, with measured Rabi splittings of 47 and 60 meV, respectively, both at 5 K and room temperature.

Thick and macroporous anodic alumina membranes for self-lubricating surface composites

Aluminum-base self-lubricating surface composites require thick and macroporous alumina membranes to add lubricants easily. The thick anodic alunima films obtained in sulfuric acid and oxalic acid are always microporous, while the macroporous films in general phosphoric acid are very thin. In this paper, thick and macroporous alumina layers were fabricated successfully with a phosphate-base solution. The anodizing process in this compound solution and the effects on the thickness of the oxide films were investigated in detail. The results indicate that the growth of porous layers in this solution undergo three stages during anodizing, same with in the general solution. This electrolyte is sensitive to anodizing temperature which affects current density in great degree. The additive (including organic carboxylic acid and Ce salt) in the phosphate-base electrolyte plays an important role on the increase of film thickness. In this compound electrolyte, the pore diameter of the anodic alumina membranes is about 100 nm in average, pore density is 18 pores μm −2 and porosity 14%. The thickness can exceed 20 μm with appropriate anodizing time and temperature.

Role of Fe and Ni Nanoparticles on Mechanical Properties of Alumina Thin Films deposited by Laser Ablation

AbstractThis paper reports our recent work on the improved mechanical properties of alumina thin films with embedded Fe and Ni nanoparticle layers. The Fe/Ni nanoparticles-alumina composite thin films have been deposited using a multi-target pulsed laser ablation technique. Every film consists of 10 layers of alumina and 9 intermediate layers of Fe or Ni nanoparticles. Alumina layer thickness kept constant (∼22 nm) and total thickness of multilayered films was in range 220-280 nm depending on metal deposition time. Composite thin films were deposited at six different substrate temperatures in the range 200-800°C. The mechanical properties measurements, performed by nanoindentation in continuous stiffness mode and applying Nix-Bhattacharya (hardness H) and King's model (Young's modulus E) for film-only properties, have shown that pure alumina films deposited at temperatures 200-500°C are relatively soft (H = 15 GPa, E = 190 GPa), while films deposited at ≥600°C are significantly harder (H = 32 GPa, E = 320 GPa). Grazing incidence XRD (GIXRD) data indicated that γ-alumina peaks exist in high temperature samples while alumina films deposited at ≥500°C were amorphous. Embedding Ni and Fe nanoparticle layers at 500°C led to significant increase of H and E (31 GPa and 365 GPa with Fe and 33 GPa and 380 GPa with Ni) and appearance of γ-alumina peaks in GIXRD. Embedding on metal nanoparticle layers does not change mechanical properties of alumina films deposited at 200°C, and significant hardening of metal containing films starts at 400°C. These results suggest that metal nanoparticles have a catalytic effect on the growth of alumina thin films with enhanced crystallinty. The effect of Ni and Fe nanoparticle size on mechanical properties of thin films has been studied times at substrate temperature 500°C using eight different metal deposition. HRTEM data have shown that metal nanopartiles have uniform particle size distribution and inter-particle separation in the layer. Size of Ni and Fe nanoparticles with highest effect on mechanical properties was 4 -6 nm.

Super-Resolution Imaging by Scanning Near-Field Optical Microscopy with Microfabricated Probes

Scanning near-field optical microscopy offers optical imaging with a resolution below the diffraction limit of &#x3BB;/2. An introduction into the concept is given and its implementation into a real instrument illustrated. The most crucial part of the instrumentation is the optical near-field probe. Our efforts concerning near-field imaging with microfabricated cantilevered probe sare reviewed. The probes are silicon beams with solid quartz tip, which is completely covered with a 60-nm thick layer of aluminum. The demonstrated contrast mechanisms comprise transmission and fluorescence. In the latter case an artifact free &#x2018;true&#x2019; optical resolution of 32 nm is shown. The influence of the polarization on the optical resolution is discussed. Best performance is achieved, when directly transmitted linear polarized is blocked and only components of radial polarized light, which originates from a supported eigenmode of the probe, is detected.

Electro-optic measurement system with high spatial resolution utilizing poled polymer film as external probe tip

A new external electro-optic probing technology has been first demonstrated using a poling electro-optic (EO) polymer film, spin-coated on 20 nm thick grounding perspective aluminum layer which sputtered on a piece of ITO glass ( 1000 μ m × 1000 μ m × 80 μ m ) as a probe tip, the aluminum layer which has 30% reflectance ratio is also a reference coating. A 1 μ m interdigital electrode was measured, and the spatial resolution of less than 0.5 μ m was obtained. Voltage sensitivity was approximately 2 mV / Hz . The probing beam reflected from the metal line is phase-modulated by the signal electric field in the EO polymer film, and then converted to amplitude modulation by interference with the reference beam reflected from the 30% reflective coating. The reference electrode makes sure that the most signal voltage drops down in the EO polymer film.

X‐ray photoelectron spectroscopic analysis of growth and thermal stability of palladium ultra thin films on alumina/NiAl(110)

AbstractWe have studied the growth and thermal stability of Pd ultra‐thin films on Al2O3/NiAl(110) in situ using x‐ray photoelectron spectroscopy. The results showed that Pd grew in a nearly layer‐by‐layer manner on the Al2O3/NiAl (110) surface at a deposition rate of 0.2 Å/min. No strong interaction between the Pd over‐layer and the substrate was observed during initial growth. After high‐temperature treatments, Pd diffused into the substrate and the alumina layer thickness increased significantly. Palladium served as a catalyst for this reaction when the temperature was lower than 570 K; PdO formed when the temperature was higher than 670 K. Copyright © 2004 John Wiley &amp; Sons, Ltd.

X-ray photoelectron spectroscopy and low-energy electron diffraction study on the oxidation of NiAl(110) surfaces at elevated temperatures

We studied the growth of ultrathin alumina films on NiAl(110) substrates at elevated temperatures using LEED and XPS. We obtained a well-ordered alumina layer without additional annealing when we introduced oxygen at a pressure of 6.6×10 −6 Pa and a substrate temperature of 1020 K. The alumina layer thicknesses were calculated using a uniform overlayer model, and 10.9 Å of the alumina layer was obtained when the oxygen dose increased to 4000 L. The binding energies of Al 2 p and O 1 s for Al 2O 3 shifted to higher binding energy synchronously when the alumina layer increased in thickness during 1020 K oxidation.

Tunnel barrier's property in magnetic tunnel junctions probed by Raman spectroscopy

By monitoring the intensity of the weak Raman peak from the Si substrate, the transmittance of the multilayer structure could be deduced. Since the samples are identical, except for the thickness of the top aluminum layer, any difference in the intensity of the Si Raman peak is due to the difference in the transmittance of the top aluminum (oxide) layer. It was found that the intensity decreases monotonically with the aluminum layer thickness, which means that there is a substantial underoxidation. Furthermore, the intensity for the 1.6 nm sample is measurably lower than that for the 0.8 nm sample, which indicates that even the optimized 1.6 nm sample may have some degree of under-oxidation. This work demonstrates that Raman spectroscopy could be a useful tool in probing the oxidation state of the aluminum oxide tunnel barriers.

Modeling of Aluminum Induced Lateral Crystallization of Hydrogenated Amorphous Silicon

ABSTRACTMetal induced lateral crystallization (MILC) of hydrogenated amorphous silicon (a-Si:H) was studied and a model was developed based on the resistance measurement of the films. Hydrogenated amorphous silicon films of 300 nm thickness were deposited using plasma enhanced chemical vapor deposition (PECVD) on oxidized p-type (100) silicon wafers. Thermally evaporated 200 nm thick aluminum layer was deposited over amorphous silicon and patterned using photolithography. The samples were annealed at different temperatures for different time periods. After annealing the resistance of amorphous silicon between aluminum pads was measured. Based on these measurements, a model was developed to predict the lateral crystallization velocity. In this model, the resistance change due to loss of hydrogen from the film was also taken into account. For this purpose, another set of experiments was conducted. In this set, hydrogenated amorphous silicon films of 300 nm thickness were deposited on Corning 7059 glass. The samples were annealed for different period of time at different temperatures. After annealing, parallel bars of silver paint were formed on the samples and the resistance of each sample was measured. The theoretically determined lateral crystallization velocity was verified using optical microscope observations and X-ray diffraction analysis and was found to be in close agreement.

Formation of highly adherent nano-porous alumina on Ti-based substrates: a novel bone implant coating.

Thin, nano-porous, highly adherent layers of anodised aluminium formed on the surface of titanium alloys are being developed as coatings for metallic surgical implants. The layers are formed by anodisation of a 1-5 microm thick layer of aluminium which has been deposited on substrate material by electron beam evaporation. The surface ceramic layer so produced is alumina with 6-8 wt % phosphate ions and contains approximately 5 x 10(8) cm(-2) pores with a approximately 160 nm average diameter, running perpendicular to the surface. Mechanical testing showed the coatings' shear and tensile strength to be at least 20 and 10 MPa, respectively. Initial cell/material studies show promising cellular response to the nano-porous alumina. A normal osteoblastic growth pattern with cell number increasing from day 1 to 21 was shown, with slightly higher proliferative activity on the nano-porous alumina compared to the Thermanox control. Scanning electron microscopy (SEM) examination of the cells on the porous alumina membrane showed normal osteoblast morphology. Flattened cells with filopodia attaching to the pores and good coverage were also observed. In addition, the pore structure produced in these ceramic coatings is expected to be suitable for loading with bioactive material to enhance further their biological properties.

放射光による遮熱コーティングの酸化損傷とはく離応力の解析

As the bond coating, NiCoCrAlY powder was atmospheric plasma-sprayed on the Ni based super-alloy (In738LC), and the thickness of the bond coating was 0.15mm. Zirconia powder with 8mass% yttria was atmospheric plasma-sprayed as the top coating, and the thickness was 0.3mm. To oxidize the specimen, the specimens were kept in air at 1373K for 0, 500, 1000 and 2000h. The cross section of each oxidized specimen was observed with a scanning electron microscope. The thermally grown oxide (TGO) consists of the alumina layer and the composite oxide layer. The thickness of alumina layer stopped to increase after 500h exposure, while the thickness of the composite oxide layer incresed monotonically. The TGO grew at the convex part of the bond coating, and pushed up the top coating. As a result, the spalling crack was initiated near the convex part. The spalling stress for each oxidized specimen was estimated by the hybrid method using the stress data obtained by laboratory X-rays and high energy synchrotron X-rays. The top coating without the oxidization did not have the spalling stress. For the oxidized specimen, the spalling stress was small beneath the surface, and steeply increased near the interface between the top and the bond coating. The spalling stress near the interface was about 200MPa. The distribution of the spalling stress for the case of the 1000h exposure was similar to that for the case of 500h. The TGO promotes the spallation of the top coating, and the distribution of the spalling stress corresponds to the observed position of spalling cracks.

Hydrogen passivation of bulk defects and surface in silicon

ABSTRACTMonocrystalline and multicrystalline silicon wafers were investigated with boron doping levels in the range 1015 cm−3 to 1016 cm−3, respectively. Hydrogenation of the samples resulted from hydrogen-rich silicon nitride deposition by plasma enhanced chemical vapour deposition on the surface of the wafers. Passivation effects are observed after annealing and evaluated using minority carrier diffusion length (L) measurements, light beam induced current scan maps and lifetime (τ) measurements, by the contact-less phase shift technique. When applied at various excitation frequencies the phase shift technique leads evaluate the surface recombination velocity (S) and the actual bulk lifetime.It was found, in multicrystalline silicon that isolated intragrain defects are well passivated while at grain boundaries and dislocation clusters deep levels are transformed into shallow levels. As a consequence L increases up to 80 % after firing the samples which the back surface was covered by a 2 μm thick aluminium layer. S decreases below 500 cm/s at the front surface covered by the hydrogen rich silicon nitride layer.

Numerical Simulation and Experimental Charcterisation of Direct Hypervelocity Impact on a Spacecraft Hybrid Carbon Fibre/Kevlar Composite Structure

This article addresses the response of GLAss fiber REinforced aluminum to hypervelocity impacts of micrometeoroid analogs at impact velocities of 7 km/s and beyond. In relation, the damage modes of different GLAss fiber REinforced aluminum configurations have been exemplified. The GLAss fiber REinforced aluminum configurations comprised six to twelve variably thick aluminum layers and up to four plies of glass fiber reinforced epoxy per composite laminate. Hypervelocity impact experiments have been conducted with the help of a two-stage light-gas gun, wherein aluminum- and stainless steel projectiles were launched at velocities up to 7.15 km/s. Visual inspection of the damage area suggested the dissipation of impact energy in elastic-plastic deformation, petalling, delamination, debonding, tensile failure of fibers, and pyrolysis of epoxy. A prevailing damage mode was not apparent albeit. The quasi-isotropic ply orientation of S2-glass/FM94-epoxy laminates promoted the interference of shock- and rarefaction waves and suppressed the damage area of GLAss fiber REinforced aluminum. To discriminate between the impact performance of different GLAss fiber REinforced aluminum configurations, the energy dissipated in different damage modes of GLAss fiber REinforced aluminum has been assessed quantitatively. In terms of normalized energy, the cross-ply GLAss fiber REinforced aluminum dissipated higher energy in petal formation than in other primary damage modes. The normalized petalling energy was found to decline with the increase of impact energy. The outcomes of this study will help to optimize the GLAss fiber REinforced aluminum laminate, which will be employed as a bumper shield to prevent the fatal damage and the unzipping of a spacecraft pressure bulkhead.

A liquid aluminum corrosion resistance surface on steel substrate

The process of hot dipping pure aluminum on a steel substrate followed by oxidation was studied to form a surface layer of aluminum oxide resistant to the corrosion of aluminum melt. The thickness of the pure aluminum layer on the steel substrate is reduced with the increase in temperature and time in initial aluminizing, and the thickness of the aluminum layer does not increase with time at given temperature when identical temperature and complete wetting occur between liquid aluminum and the substrate surface. The thickness of the Fe–Al intermetallic layer on the steel base is increased with increasing bath temperature and time. Based on the experimental data and the mathematics model developed by the study, a maximum exists in the thickness of the Fe–Al intermetallic at certain dipping temperature. X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis reveals that the top portion of the steel substrate is composed of a thin layer of α-Al2O3, followed by a thinner layer of FeAl3, and then a much thicker one of Fe2Al5 on the steel base side. In addition, there is a carbon enrichment zone in diffusion front. The aluminum oxide surface formed on the steel substrate is in perfect condition after corrosion test in liquid aluminum at 750°C for 240h, showing extremely good resistance to aluminum melt corrosion.

A model for dislocation behavior during deformation of Al/Al 3Sc (fcc/L1 2) metallic multilayers

In previously published work, we have reported on the microstructure and indentation hardness of nanoscale Al/Al 3Sc multilayers. In this paper, the large increases in hardness that were observed with decreasing aluminum layer thickness are analyzed in detail and several simple dislocation mechanisms are proposed to describe the behavior. Strengthening can be explained by assuming that yielding occurs first by forming dislocation loops in the aluminum layers—the dislocations are constrained by layers of Al 3Sc. We show that the anti-phase boundary (APB) energy of the L1 2 Al 3Sc structure can be used to quantify the resistance of the interfaces in the multilayer structure to dislocation motion and that the thickness of the Al 3Sc layer also plays an important role in determining the strengthening response.

Growth and oxidation of a Ni 3Al alloy on Ni(1 0 0)

The growth and oxidation of a thin film of Ni 3Al grown on Ni(1 0 0) were studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and high resolution electron energy loss spectroscopy (EELS). At 300 K, a 12 Å thick layer of aluminium was deposited on a Ni(1 0 0) surface and subsequently annealed to 1150 K resulting in a thin film of Ni 3Al which grows with the (1 0 0) plane parallel to the (1 0 0) surface of the substrate. Oxidation at 300 K of Ni 3Al/Ni(1 0 0) until saturation leads to the growth of an aluminium oxide layer consisting of different alumina phases. By annealing up to 1000 K, a well ordered film of the Al 2O 3 film is formed which exhibits in the EEL spectra Fuchs–Kliewer phonons at 420, 640 and 880 cm −1. The LEED pattern of the oxide shows a twelvefold ring structure. This LEED pattern is explained by two domains with hexagonal structure which are rotated by 90° with respect to each other. The lattice constant of the hexagonal structure amounts to ∼2.87 Å. The EELS data and the LEED pattern suggest that the γ ′-Al 2O 3 phase is formed which grows with the (1 1 1) plane parallel to the Ni(1 0 0) surface.

Properties of pseudo surface acoustic wave on (-74/spl deg/)YX cut quartz

Pseudo surface acoustic wave properties on (-74/spl deg/)YX cut quartz have been calculated and measured. It was found that this cut belongs to the minimal diffraction cuts, and the reflection coefficient of a single aluminium electrode is about four times larger compared to that of the ST cut. Temperature compensation exists if, for a given aluminium layer thickness, a proper free surface length is used. This cut is free of spurious transverse modes.