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Diffusion Barrier (diffusion + barrier)
Selected AbstractsVoid formation in the Cu layer during thermal treatment of SiNx/Cu/Ta73Si27/SiO2/Si systemsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Hübner Abstract The thermal stability of a SiNx passivation layer and its influence on the annealing behavior of an amorphous Ta73Si27 diffusion barrier deposited between copper and SiO2 were analyzed by X-ray diffraction, glow discharge optical emission spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. During heat treatment at a temperature Tan = 500 °C, diffusion of Cu atoms out of the Cu metallization into the SiNx passivation occurs. The Cu diffusion intensifies with increasing annealing temperature and annealing time and seems to be a necessary precondition for a defect formation process observed within the Cu metallization. Depending on the chemical composition of the SiNx/Cu interface, voids in the ,m-range can be formed within the Cu film. Compared to an unpassivated sample, heat treatment leads to a reduced diffusion of Ta atoms from the barrier through the copper into the SiNx/Cu interface. The barrier crystallization process into Ta5Si3 occurring during annealing at Tan = 600 °C is principally not affected by the presence of a SiNx passivation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Augmentation of all- trans -retinoic acid concentration in plasma by preventing inflammation responses induced by atRA-loaded microspheres with concurrent treatment of dexamethasoneDRUG DEVELOPMENT RESEARCH, Issue 4 2004Kyeongsoon Park Abstract All- trans retinoic acid (atRA)-loaded microspheres severely induce inflammatory responses after microsphere implantation. Fibroblasts and a thick band of fibrous capsule resulting from the inflammatory responses could hamper drug permeation to the bloodstream because fibroblasts actively metabolize atRA into polar metabolites and the thick fibrous capsule acts as a diffusion barrier. In the present study, we investigated whether the fibroblast proliferation and collagen deposition induced by atRA released from microspheres might affect the atRA concentration in plasma and atRA metabolism with or without treatment of dexamethasone as an anti-inflammatory drug. After subcutaneous injection of atRA-loaded microspheres in rats, it was observed that atRA-loaded microspheres induced severe inflammatory responses and stimulated fibroblast proliferation and collagen deposition in fibrous capsules. On the other hand, the orally treated dexamethasone effectively prevented inflammatory responses in a dose-dependent manner and suppressed about 49% of the number of fibroblasts and collagen deposition in fibrous capsules at 14 days. In addition, after the treatment of dexamethasone, the atRA concentration in plasma was increased, and its metabolism was decreased approximately by 40% at 7 days, compared to the group treated alone with atRA-loaded microspheres. In conclusion, the concurrent treatment of dexmethasone with atRA-loaded microspheres could prevent inflammatory responses and metabolism of atRA, thereby maintaining the atRA concentration in plasma for longer periods in the therapeutic range. Drug Dev. Res. 61:197,206, 2004. © 2004 Wiley-Liss, Inc. [source] Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?ENVIRONMENTAL MICROBIOLOGY, Issue 7 2009Lucas J. Stal Summary Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A,C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas. [source] Oxidation Resistant Coatings for Ultrahigh Temperature Refractory Mo-Base Alloys,ADVANCED ENGINEERING MATERIALS, Issue 11 2009John H. Perepezko The use of Mo base alloys is limited by severe oxidation above about 650,°C. While MoSi2 coatings offer protection at high temperature, they are ineffective at low temperature. An integrated coating design has been developed based upon (B,+,Si) co-deposition and an in-situ diffusion barrier that offers robust, long term oxidation protection and self-healing for Mo alloys over a wide temperature range to over 1600,°C. [source] Microgel-Based Engineered Nanostructures and Their Applicability with Template-Directed Layer-by-Layer Polyelectrolyte Assembly in Protein EncapsulationMACROMOLECULAR BIOSCIENCE, Issue 5 2005Dinesh B. Shenoy Abstract Summary: A novel strategy for the fabrication of microcapsules is elaborated by employing biomacromolecules and a dissolvable template. Calcium carbonate (CaCO3) microparticles were used as sacrificial templates for the two-step deposition of polyelectrolyte coatings by surface controlled precipitation (SCP) followed by the layer-by-layer (LbL) adsorption technique to form capsule shells. When sodium alginate was used for inner shell assembly, template decomposition with an acid resulted in simultaneous formation of microgel-like structures due to calcium ion-induced gelation. An extraction of the calcium after further LbL treatment resulted in microcapsules filled with the biopolymer. The hollow as well as the polymer-filled polyelectrolyte capsules were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and scanning force microscopy (SFM). The results demonstrated multiple functionalities of the CaCO3 core , as supporting template, porous core for increased polymer accommodation/immobilization, and as a source of shell-hardening material. The LbL treatment of the core-inner shell assembly resulted in further surface stabilization of the capsule wall and supplementation of a nanostructured diffusion barrier for encapsulated material. The polymer forming the inner shell governs the chemistry of the capsule interior and could be engineered to obtain a matrix for protein/drug encapsulation or immobilization. The outer shell could be used to precisely tune the properties of the capsule wall and exterior. Confocal laser scanning microscopy (CLSM) image of microcapsules (insert is after treating with rhodamine 6G to stain the capsule wall). [source] Effect of the dimer structure on indium adsorption and diffusion on a GaSb surfacePHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7-8 2009Min Xiong Abstract The adsorption properties and surface diffusion of an indium adatom on a GaSb(001)-(2 × 3) structure have been studied using first-principles calculations. We find that the indium adatoms are preferentially adsorbed in the low energy trenches along the [110] direction at bridge positions of surface dimers. Besides, the adsorption sites connecting these trenches along [110] present distinct properties for different surface dimer structures. For the structure with Sb,Sb homodimers, the dimer arrangement reduces significantly the adatom diffusion barrier along the [110] direction and the calculations on diffusion coefficients demonstrate that [110] is the fast diffusion direction. While on the structure with Ga,Sb heterodimers, the adsorption sites are separated by the heterodimers causing a considerable diffusion barrier and [10] becomes the fast diffusion direction accordingly. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Vertical-type InGaN/GaN light emitting diodes with high efficiency reflector ITO/APC alloy on p-GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Sung Min Hwang Abstract We demostrate the efficient p-type reflector for high performance vertical InGaN/GaN light emitting diodes (LEDs) with 1 × 1mm2 chip size. The reflector consists of Indium-Tin-Oxide (ITO) and Ag-Pd-Cu (APC) alloy. The ITO was inserted between p-GaN layer and APC alloy using RF magnetron sputtering to prevent inter-diffusion of APC into GaN layer. Transmission electron microscopy (TEM) result shows that ITO plays an impotant role as a diffusion barrier to APC alloy. In addition, the contact resistivity of ITO to p-GaN layer was measured to be 1.32 × 10 -3 ,cm2 at annealing temperature of 600 °C for 1 minute. APC alloy was adpoted to acheive a higher reflectance for improvement of a light extraction efficiency. The APC alloy reflector appeared to have a higher reflectivity compared to conventional Ni/Ag film reflector. The verical LEDs with ITO/APC alloy reflectors showed the light-output power of 295 mW at an injection current of 350 mA, which is 15% higher than that with Ni/Ag reflectors. The output power enhancement is attributed to the increase of light extraction efficiency due to high reflectivity of APC alloy (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transparent Ohmic Contacts on p-GaN Using an Indium Tin Oxide OverlayerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003Soo Young Kim Abstract We report a low-resistant, thermally stable ohmic contact on p-GaN using a promising contact scheme of Ni/Au/ITO. Ni/Au contact on p-GaN was annealed at 500 °C under an oxidizing atmosphere before ITO deposition, forming a NiO layer acting as a diffusion barrier of In atoms from ITO. Specific contact resistivity as low as 4.8 × 10,4 ,cm2 was obtained from the Ni (20 Å)/Au (30 Å)/ITO (1000 Å) contact annealed at 500 °C under an oxidizing atmosphere. Contact resistivity is decreased due to crystallization of ITO and Au indiffusion through the NiO layer after annealing at 500 °C under an oxidizing ambient. Also, under this condition, the measured optical transmittance of Ni/Au/ITO was above 80% at a wavelength of 470 nm. [source] Reactive oxygen species and antioxidants in legume nodulesPHYSIOLOGIA PLANTARUM, Issue 4 2000Manuel Becana Reactive oxygen species are a ubiquitous danger for aerobic organisms. This risk is especially elevated in legume root nodules due to the strongly reducing conditions, the high rates of respiration, the tendency of leghemoglobin to autoxidize, the abundance of nonprotein Fe and the presence of several redox proteins that leak electrons to O2. Consequently, nodules are particularly rich in both quantity and diversity of antioxidant defenses. These include enzymes such as superoxide dismutase (EC 1.15.1.1) and ascorbate peroxidase (EC 1.11.1.11) and metabolites such as ascorbate and thiol tripeptides. Nodule antioxidants have been the subject of intensive molecular, biochemical and functional studies that are reviewed here. The emerging theme is that antioxidants are especially critical for the protection and optimal functioning of N2 fixation. We hypothesize that this protection occurs at least at two levels: the O2 diffusion barrier in the nodule parenchyma (inner cortex) and the infected cells in the central zone. [source] Theoretical study on adsorption and diffusion of N atoms on Cu low-index surfaceCHINESE JOURNAL OF CHEMISTRY, Issue 11 2004Zhao-Yu Diao Abstract The adsorption and diffusion of N atoms on the three low-index Cu planes were studied using 5-parameter Morse potential (5-MP) method, and the best theory-experiment agreement was obtained. N atom of Cu(100) surface sit on the fourfold hollow site with the vertical height of 0.018 nm closely coplanar with the topmost copper layer, and the four CuN bond lengths are 0.182 nm and the fifth CuN distance is 0.199 nm. For Cu(111) system, the existence of aberrant Cu(100) reconstructed structure is approved at higher coverage, and at low coverage the structure is almost an ideal Cu(111) surface structure. With respect to Cu(110) system, the N atoms are adsorbed at LB and H3 sites, not at SB site. The diffusion passage and diffusion barrier of adsorbed N atoms were also studied. [source] Bottom-Up Engineering of Subnanometer Copper Diffusion Barriers Using NH2 -Derived Self-Assembled MonolayersADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Arantxa Maestre Caro Abstract A 3-aminopropyltrimethoxysilane-derived self-assembled monolayer (NH2SAM) is investigated as a barrier against copper diffusion for application in back-end-of-line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO2 dielectric substrate and the Cu over-layer. Time-of-flight secondary ion mass spectrometry and X-ray spectroscopy (XPS) analysis reveal that the copper over-layer closes at 1,2-nm thickness, comparable with the 1.3-nm closure of state-of-the-art Ta/TaN Cu diffusion barriers. That the NH2SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy-filtered transmission electron microscopy supported by XPS. The SAM forms a well-defined carbon-rich interface with the Cu over-layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH2SAM/SiO2 system increases with annealing temperature up to 7.2,J m,2 at 400,°C, comparable to Ta/TaN (7.5,J m,2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH2SAM is a suitable candidate for subnanometer-scale diffusion barrier application in a selective coating for copper advanced interconnects. [source] Periodontitis as an infectious disease: specific features and their implicationsORAL DISEASES, Issue 2003A Mombelli Periodontitis may be viewed as an infectious disease with a number of specific characteristics. Pathogens of the subgingival microbiota can interact with host tissues even without direct tissue penetration. Hence, antimicrobial agents must be available at a sufficiently high concentration not only within the periodontal tissues, but also outside, in the environment of the periodontal pocket. The subgingival microbiota accumulate on the root surface to form an adherent layer of plaque with the characteristics of a biofilm. Several mechanisms, such as diffusion barriers, and selective inactivation of agents lead to an increased resistance of bacteria in biofilms. Mechanical supragingival plaque control is indispensable to prevent the re-emergence of periodontal pathogens and the re-establishment of a biofilm in treated sites. Since specific features have important implications for the use of antimicrobial agents in periodontal therapy, extrapolations from experiences made in the therapy of other infections are only partially valid. The ultimate evidence for the efficacy of systemic or local chemotherapy must be obtained from treatment studies in humans with adequate follow-up. [source] Spectroscopic ellipsometry study of thin diffusion barriers of TaN and Ta for Cu interconnects in integrated circuitsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008S. Rudra Abstract The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV,visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73,8.7 eV and the dielectric functions were simulated using Drude,Lorentz model and effective medium approximation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the ,-phase of Ta, it turned out to be a mixture of ,- and ,-phases with higher contribution of the ,-phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic properties of spin valves having extremely thin underlayersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2007Jiwon Kim Abstract Magnetic properties of spin valve elements having Mo(N) and Ta(N) underlayers were studied by varying their thickness. Spin valve structure was Si/SiO2/Underlayer(tÅ)/NiFe(21 or 42Å)/CoFe(28Å)/Cu(22Å)/CoFe(18Å)/IrMn(65Å)/Ta(25Å). Spin valve elements having exteremely thin Mo(N) and Ta(N) underlayers showed high MR ratio of about 7 - 8%. Annealing of such spin valve elements having underlayer thickness of 7 to 8 Å showed comparable behavior with the spin valve elements with thicker (35Å) underlayer, which can be utilized to reduce overall device thickness. Also, it was found that Mo(N) underlayers for spin valve elements may be used as diffusion barriers between Si substrate and ensuing active spin valve layers, simultaneously. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reining in cytokinesis with a septin corralBIOESSAYS, Issue 1 2005Fern P. Finger Septins are a family of conserved GTP-binding proteins that function in cytokinesis in fungi and animals. In budding yeast, septins form scaffolds for assembly of the actomyosin contractile ring at the cleavage plane, a role that does not appear to be conserved in other organisms. The septins form an hourglass-shaped collar at the mother-bud neck, which splits into two rings flanking the division plane at cytokinesis. A recent study1 demonstrates that these two septin rings constitute diffusion barriers that create a cytokinetic compartment to retain cortical cytokinetic factors in proximity to the cleavage plane. BioEssays 27:5,8, 2005. © 2004 Wiley Periodicals, Inc. [source] | |||||||||||||||||||