Showing papers on "Barrier layer published in 2010"

Reverse side engineered iii-nitride devices

Abstract: Group III-nitride devices are described that include a stack of III-nitride layers, passivation layers, and conductive contacts. The stack includes a channel layer with a 2DEG channel, a barrier layer and a spacer layer. One passivation layer directly contacts a surface of the spacer layer on a side opposite to the channel layer and is an electrical insulator. The stack of III-nitride layers and the first passivation layer form a structure with a reverse side proximate to the first passivation layer and an obverse side proximate to the barrier layer. Another passivation layer is on the obverse side of the structure. Defected nucleation and stress management layers that form a buffer layer during the formation process can be partially or entirely removed.

Semiconductor device having damascene interconnection structure that prevents void formation between interconnections having transparent dielectric substrate

Abstract: A semiconductor device is made up of a first insulating layer having a through hole; a first interconnection which includes a first conductive layer, a first barrier layer, and a first main interconnection, and a second interconnection connected to one of the first conductive layer and the first barrier layer. Accordingly, the semiconductor device can avoid a problem where the material of the first main interconnection transfers from a portion connected to the second interconnection due to electromigration to form a void, with the result that the first interconnection is disconnected from the second interconnection.

High performance MTJ element for STT-RAM and method for making the same

Abstract: A STT-MTJ MRAM cell that utilizes transfer of spin angular momentum as a mechanism for changing the magnetic moment direction of a free layer includes an IrMn pinning layer, a SyAP pinned layer, a naturally oxidized, crystalline MgO tunneling barrier layer that is formed on an Ar-ion plasma smoothed surface of the pinned layer and, in one embodiment, a free layer that comprises an amorphous layer of Co60Fe20B20 of approximately 20 angstroms thickness formed between two crystalline layers of Fe of 3 and 6 angstroms thickness respectively or on a single such layer. The free layer is characterized by a low Gilbert damping factor and by very strong polarizing action on conduction electrons. The resulting cell has a low critical current, a high dR/R and a plurality of such cells will exhibit a low variation of both resistance and pinned layer magnetization angular dispersion.

Method and system for providing a spin tunneling magnetic element having a crystalline barrier layer

Abstract: The method and system for providing a spin tunneling element are disclosed. The method and system include depositing a pinned layer, a barrier layer, and a free layer. The barrier layer has a first crystal structure and a texture. The free layer includes a first ferromagnetic layer and a second ferromagnetic layer. The first ferromagnetic is adjacent to the second ferromagnetic layer and between the second ferromagnetic layer and the barrier layer. The first ferromagnetic layer has the first crystal structure and the texture, while the second ferromagnetic layer has a second crystal structure different from the first crystal structure.

High-flux Thin-film Nanofibrous Composite Ultrafiltration Membranes Containing Cellulose Barrier Layer

Abstract: A novel class of thin-film nanofibrous composite (TFNC) membrane consisting of a cellulose barrier layer, a nanofibrous mid-layer scaffold, and a melt-blown non-woven substrate was successfully fabricated and tested as an ultrafiltration (UF) filter to separate an emulsified oil and water mixture, a model bilge water for on-board ship bilge water purification. Two ionic liquids: 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate, were chosen as the solvent to dissolve cellulose under mild conditions. The regenerated cellulose barrier layer exhibited less crystallinity (determined by wide-angle X-ray diffraction, WAXD) than the original cotton linter pulps, but good thermal stability (determined by thermal gravimetric analysis, TGA). The morphology, water permeation, and mechanical stability of the chosen TFNC membranes were thoroughly investigated. The results indicated that the polyacrylonitrile (PAN) nanofibrous scaffold was partially imbedded in the cellulose barrier layer, which enhanced the mechanical strength of the top barrier layer. The permeation flux of the cellulose-based TFNC membrane was significantly higher (e.g. 10×) than comparable commercial UF membranes (PAN10 and PAN400, Sepro) with similar rejection ratios for separation of oil/water emulsions. The molecular weight cut-off (MWCO) of TFNC membranes with cellulose barrier layer was evaluated using dextran feed solutions. The rejection was found to be higher than 90% with a dextran molecular weight of 2000 KDa, implying that the nominal pore size of the membrane was less than ∼50 nm. High permeation flux was also observed in the filtration of an emulsified oil/water mixture as well as of a sodium alginate aqueous solution, while high rejection ratio (above 99.5%) was maintained after prolonged operation. A variation of the barrier layer thickness could dramatically affect the permeation flux and the rejection ratio of the TFNC membranes, while different sources of cellulose, ionic liquids, and non-woven supports did not. As ionic liquids can be recycled and reused without obvious decomposition, the chosen method also demonstrates a benign pathway to fabricate the cellulose barrier layer for other types of membranes.

Light emitting device

Abstract: PROBLEM TO BE SOLVED: To provide a light emitting device having a forbidden band width of an active layer whose temperature variation is reduced. SOLUTION: The light emitting deice includes an active layer provided with a quantum dot formed of a first material whose forbidden band width becomes wider with temperature rise, and a barrier layer formed of a second material whose forbidden band width becomes narrower with temperature rise and having the quantum dot embedded therein. COPYRIGHT: (C)2010,JPO&INPIT

Non-planar germanium quantum well devices

Abstract: Techniques are disclosed for forming a non-planar germanium quantum well structure. In particular, the quantum well structure can be implemented with group IV or III-V semiconductor materials and includes a germanium fin structure. In one example case, a non-planar quantum well device is provided, which includes a quantum well structure having a substrate (e.g. SiGe or GaAs buffer on silicon), a IV or III-V material barrier layer (e.g., SiGe or GaAs or AlGaAs), a doping layer (e.g., delta/modulation doped), and an undoped germanium quantum well layer. An undoped germanium fin structure is formed in the quantum well structure, and a top barrier layer deposited over the fin structure. A gate metal can be deposited across the fin structure. Drain/source regions can be formed at respective ends of the fin structure.

Low On-Resistance High-Breakdown Normally Off AlN/GaN/AlGaN DHFET on Si Substrate

Abstract: Ultrathin-barrier normally off AlN/GaN/AlGaN double-heterostructure field-effect transistors using an in situ SiN cap layer have been fabricated on 100-mm Si substrates for the first time. The high 2DEG density in combination with an extremely thin barrier layer leads to enhancement-mode devices with state-of-the-art combination of specific on-resistance that is as low as 1.25 m?·cm2 and breakdown voltage of 580 V at V GS = 0 V . Despite the 2-?m gate length used, the transconductance peaks above 300 mS/mm. Furthermore, pulsed measurements show that the devices are dispersion free up to high drain voltage V DS = 50 V. More than 200 devices have been characterized in order to confirm the reproducibility of the results.

Front to back resistive random access memory cells

Abstract: A resistive random access memory device formed on a semiconductor substrate comprises an interlayer dielectric having a via formed therethrough. A chemical-mechanical-polishing stop layer is formed over the interlayer dielectric. A barrier metal liner lines walls of the via. A conductive plug is formed in the via. A first barrier metal layer is formed over the chemical-mechanical-polishing stop layer and in electrical contact with the conductive plug. A dielectric layer is formed over the first barrier metal layer. An ion source layer is formed over the dielectric layer. A dielectric barrier layer is formed over the ion source layer, and includes a via formed therethrough communicating with the ion source layer. A second barrier metal layer is formed over the dielectric barrier layer and in electrical contact with the ion source layer. A metal interconnect layer is formed over the barrier metal layer.

Optical emission spectroscopy studies of discharge mechanism and plasma characteristics during plasma electrolytic oxidation of magnesium in different electrolytes

Abstract: The discharge mechanism of the plasma electrolytic oxidation (PEO) process in different electrolytes was investigated by examining the variation of the optical emission spectra (OES) The spectrum of active species existed in the bubble layer The bubble layer was initially broken down, followed by the breakdown of the dielectric barrier layer Breakdown is the initial stage of discharge A micro-discharge formation model, which assumes that the discharge ignition in the bubble layer developed at the oxide/electrolyte interface, was proposed The active plasma species that appeared in different electrolytes during the PEO process were also studied The appearance order of the excited active plasma species depended on the energy that the orbit transition of the species needed, but was not related to the anion concentration in the electrolyte The anions in the electrolyte, except the OH − , also had little influence on the composition of the active plasma species during the PEO process The active plasma species were mainly composed of metal atoms, metal cations, and gases produced by water decomposition The electron temperature of the excited hydrogen was between 6 × 10 3 and 3 × 10 4 K The high temperature provided the possibility of ceramic film melting and sintering The source and transition of the active plasma species were also studied They were found to undergo dissociation, ionization, and excitation processes

Cathode-Electrolyte Interfaces with CGO Barrier Layers in SOFC

Abstract: Electron microscopy characterization across the cathode-electrolyte interface of two different types of intermediate temperature solid oxide fuel cells (IT-SOFC) is performed to understand the origin of the cell performance disparity. One IT-SOFC cell had a sprayed-cosintered Ce(0.90)Gd(0.01)O(1.95) (CGO10) barrier layer, the other had a barrier layer deposited by pulsed laser deposition (PLD) CGO10. Scanning electron microscopy, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) investigations conclude that the major source of the cell performance difference is attributed to CGO-YSZ interdiffusion in the sprayed-cosintered barrier layer. From TEM and EBSD work, a dense CGO10 PLD layer is found to be deposited epitaxially on the 8YSZ electrolyte substrate-permitting a small amount of SrZrO(3) formation and minimizing CGO-YSZ interdiffusion.

Nitride based semiconductor optical device, epitaxial wafer for nitride based semiconductor optical device, and method of fabricating semiconductor light-emitting device

Abstract: In the nitride based semiconductor optical device LE1, the strained well layers 21 extend along a reference plane SR1 tilting at a tilt angle α from the plane that is orthogonal to a reference axis extending in the direction of the c-axis. The tilt angle α is in the range of greater than 59 degrees to less than 80 degrees or greater than 150 degrees to less than 180 degrees. A gallium nitride based semiconductor layer P is adjacent to a light-emitting layer SP− with a negative piezoelectric field and has a band gap larger than that of a barrier layer. The direction of the piezoelectric field in the well layer W3 is directed in a direction from the n-type layer to the p-type layer, and the piezoelectric field in the gallium nitride based semiconductor layer P is directed in a direction from the p-type layer to the n-type layer. Consequently, the valence band, not the conduction band, has a dip at the interface between the light-emitting layer SP− and the gallium nitride based semiconductor layer P.

Oxidation and the origin of the two-dimensional electron gas in AlGaN/GaN heterostructures

Abstract: The surface of the AlGaN barrier layer in AlGaN/GaN high electron mobility transistors has strong and hitherto unexplained effects on transistor characteristics. Indeed, it has been cited as the source of the two-dimensional electron gas at the AlGaN/GaN interface. Using computational methods based on density functional theory, we investigate surface reconstructions on realistic GaN and AlN (0001) surfaces, which are invariably oxidized. Numerous structures with different oxide coverage and different stoichiometry are examined, and their stability is interpreted in terms of driving mechanisms such as the electron counting rule and oxide-stoichiometry matching. We discuss which structures are likely to form under a variety of oxidation conditions, and show that these structures explain the observed dependence of electron density on thickness and variations in surface barrier height.

Thin-film transistor substrate and method of fabricating the same

Abstract: A thin film transistor (TFT) substrate and a method of fabricating the same are provided. The thin film transistor substrate may have low resistance characteristics and may have reduced mutual diffusion and contact resistance between an active layer pattern and data wiring. The thin film transistor substrate may include gate wiring formed on an insulating substrate. Oxide active layer patterns may be formed on the gate wiring and may include a first substance. Data wiring may be formed on the oxide active layer patterns to cross the gate wiring and may include a second substance. Barrier layer patterns may be disposed between the oxide active layer patterns and the data wiring and may include a third substance.

Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions

Abstract: Using a ferroelectric barrier as a functional material in a (magnetic) tunnel junction has recently attracted significant interest due to new functionalities not available in conventional tunnel junctions. Switching a ferroelectric polarization of the barrier alters conductance resulting in a tunneling electroresistance (TER) effect. Using a ferroelectric barrier in a magnetic tunnel junction makes it mutiferroic where TER coexists with tunneling magnetoresistance (TMR). Here we develop a simple model for a multiferroic tunnel junction (MFTJ) which consists of two ferromagnetic electrodes separated by a ferroelectric barrier layer. The model explicitly includes the spin-dependent screening potential and thus extends previously developed models for FTJs and MFTJs. Our results demonstrate that the effect of spin-dependent screening may be sizable and may provide significant contributions to TMR and TER in MFTJs. We find that, similar to FTJs with a composite (ferroelectric/dielectric) barrier layer, the TER in a MFTJ with such a barrier is dramatically enhanced indicating that the resistance ratio between the states corresponding to the opposite polarization orientations may be as high as ${10}^{4}$ and even higher. Our results demonstrate the possibility of four resistance states in MFTJs with a pronounced difference in resistance and a possibility to control these resistance by an electric field (through ferroelectric polarization of the barrier) and by a magnetic field (through magnetization configuration of the electrodes). These functionalities may be interesting to device applications of MFTJs.

Highly efficient electro-optic polymers through improved poling using a thin TiO2-modified transparent electrode

Abstract: A sol-gel derived thin titanium dioxide (TiO2) layer was spin-coated onto indium-tin-oxide substrate to improve poling efficiency of recently developed electro-optic (E-O) polymers. The thin TiO2 layer significantly blocks excessive charge injection and reduces the leakage current during high field poling. Ultralarge E-O coefficients, up to 160–350 pm/V at 1310 nm, have been achieved. These results show higher poling efficiency (enhancement of 26%–40%) compared to the results of poled films without the TiO2 layer. This enhancement can be explained by field distribution flattening effect at high injection barrier with the insertion of TiO2 barrier layer.

Plasma electrolytic oxidation of a zirconium alloy under AC conditions

Abstract: The microstructures of zirconia coatings formed by plasma electrolytic oxidation of a zirconium alloy, Zirlo, under AC conditions in an alkaline silicate electrolyte have been examined by scanning and transmission electron microscopies. The coatings are shown to consist of three layers. The innermost barrier layer is relatively thin, up to 500 nm in a 100 µm-thick coating formed for 3600 s. The intermediate layer, constituting the main part of the coatings, consists primarily of monoclinic and tetragonal zirconia. The outer, loose layer is rich in silicon species and constitutes a reduced proportion of the coating thickness at increased time of treatment. The porous intermediate and outer layers are readily permeated by the electrolyte. The formation of the coating accounts for

Fabricating a magnetic tunnel junction storage element

Abstract: Methods for forming a magnetic tunnel junction (MTJ) storage element and MTJ storage elements formed are disclosed. The MTJ storage element includes a MTJ stack having a pinned layer stack, a barrier layer and a free layer. An adjusting layer is formed on the free layer, such that the free layer is protected from process related damages. A top electrode is formed on the adjusting layer and the adjusting layer and the free layer are etched utilizing the top electrode as a mask. A spacer layer is then formed, encapsulating the top electrode, the adjusting layer and the free layer. The spacer layer and the remaining portions of the MTJ stack are etched. A protective covering layer is deposited over the spacer layer and the MTJ stack.

The Point Defect Model for Bi-Layer Passive Films

Abstract: The Point Defect Model (PDM) has been shown to accurately describe the properties of passive films that form on metal surfaces in contact with aggressive environments under both open circuit and anodic polarization conditions. However, the commonly-employed PDM, known henceforth as PDM-II assumes that passivity arises from the properties of the barrier layer and that the outer layer, if present, contributes negligibly to the interfacial impedance. In this paper, we describe PDM-III, in which a resistive outer layer exists on the surface and contributes substantially to the impedance of the interface. The outer layer is shown to have a profound impact on the properties of the barrier layer and under certain circumstances the barrier layer is predicted to disappear. This new form of depassivation has been observed experimentally. The use of electrochemical impedance spectroscopy to characterize passive films having resistive outer layers is describe and illustrated with reference to the passive state on zirconium in simulated PWR (Pressurized Water Reactor) primary coolant.

Low-voltage indium gallium zinc oxide thin film transistors on paper substrates

Abstract: We have fabricated bottom-gate amorphous (α-) indium-gallium-zinc-oxide (InGaZnO4) thin film transistors (TFTs) on both paper and glass substrates at low processing temperature (≤100 °C). As a water and solvent barrier layer, cyclotene (BCB 3022–35 from Dow Chemical) was spin-coated on the entire paper substrate. TFTs on the paper substrates exhibited saturation mobility (μsat) of 1.2 cm2 V−1 s−1, threshold voltage (VTH) of 1.9 V, subthreshold gate-voltage swing (S) of 0.65 V decade−1, and drain current on-to-off ratio (ION/IOFF) of ∼104. These values were only slightly inferior to those obtained from devices on glass substrates (μsat∼2.1 cm2 V−1 s−1, VTH∼0 V, S∼0.74 V decade−1, and ION/IOFF=105–106). The uneven surface of the paper sheet led to relatively poor contact resistance between source-drain electrodes and channel layer. The ability to achieve InGaZnO TFTs on cyclotene-coated paper substrates demonstrates the enormous potential for applications such as low-cost and large area electronics.

Effects of barrier layers on device performance of high mobility In0.7Ga0.3As metal-oxide-semiconductor field-effect-transistors

Abstract: We have applied single InP barrier layer with different thicknesses and InP/In0.52Al0.48As double-barrier layer to In0.7Ga0.3As Al2O3 metal-oxide-semiconductor field-effect-transistors (MOSFETs) and investigated their effects on device performance. In0.7Ga0.3As MOSFETs with 3 nm InP single-barrier attain 22% higher peak effective mobility while devices with 5 nm InP attain 58% higher peak mobility than the ones without barrier. Devices using InP/In0.52Al0.48As double-barrier achieve mobility enhancement at both low-field (68% at peak mobility) and high-field (55%) compared to ones without barrier. High channel mobility of 4729 cm2/V s has been obtained using InP/In0.52Al0.48As barrier and atomic-layer-deposited Al2O3 gate oxide.

SrTiO3 Recombination-Inhibiting Barrier Layer for Type II Dye-Sensitized Solar Cells

Abstract: Type II dye-sensitized solar cells (DSSCs) differ from conventional DSSCs by their mechanism of light absorption and electron injection. Instead of photoexcitation of the dye, followed by electron injection to the semiconductor conduction band, in type II DSSCs, there is a direct electron injection from the HOMO level of the sensitizer into the conduction band of the semiconductor. The main drawback of such cells is their extremely rapid back-electron-transfer rate. Herein, we present a new approach for inhibiting back electron transfer in a catechol-sensitized type II DSSC using a thin layer barrier coating of SrTiO3 between the semiconductor and the sensitizer. A 70% improvement in charge collection efficiency is reported. A proposed mechanism for the operation of the SrTiO3 barrier layer is presented.

Study on quaternary AlInGaN/GaN HFETs grown on sapphire substrates

Abstract: We report on AlInGaN/GaN heterostructure field effect transistors (HFETs) and the effect of different barrier material compositions. The analytical model for the interface charge in quaternary nitride heterostructures is described in detail and is applied in the calculation of the expected sheet carrier density. Experimental results from different lattice-matched AlInGaN/GaN heterostructures are presented and compared with the analytical predictions. Three heterostructures with AlInGaN barriers grown on sapphire substrates were processed and have been investigated. Each barrier layer was lattice-matched to GaN and the gallium content was 0.1, 0.15 and 0.2 at a barrier thickness of 13.5, 12.8 and 11.3 nm, respectively. Additionally, from these experiments, the basic trends for quaternary nitride Schottky barrier contacts are discussed. Finally, comprehensive dc characterizations have been performed. All devices had a gate length of 1 µm and exhibited a good transconductance of around 260 mS mm−1 at nearly the same current density level. An increase in threshold voltage as well as a decrease in gate leakage current for increasing GaN content has been observed. The nearly constant electron mobility in the range of 1700 cm2 V−1 s−1 at room temperature is within the best reported so far for HFETs with InN-containing barriers.

Organic light emitting device and manufacturing method thereof

Abstract: PURPOSE: An organic light emitting device and a method for manufacturing the same are provided to improve a moisture preventive property and surface roughness by forming a barrier layer which includes a stack comprising a silicon oxide film and a silicon oxynitride film. CONSTITUTION: A barrier layer is formed on a substrate. A silicon oxynitirde inorganic film is stacked on a silicon oxide inorganic film in order to form the barrier layer. The density of the silicon oxynitride inorganic film is higher than that of the silicon oxide inorganic film. A first electrode is formed on the barrier layer. A second electrode is formed on the first electrode. An organic film is formed between the first electrode and the second electrode.

Phosphor sheet, a diffusion plate, an illuminating device, and a display unit

Abstract: A phosphor sheet having a laminated structure including a first barrier material, a first barrier material, a first color conversion layer, a second color conversion layer, and a second barrier layer and a display unit and an illuminating device including display unit is provided. A diffusion plate and a display unit including a diffusion plate are also provided.