Ir Layer Research Articles

잠수함의 비음향 스텔스 기법에 관한 연구

잠수함이 가장 취약한 시기는 잠수함이 스노클이나 잠망경 운용을 위하여 잠망경 심도로 항해할 경우이며, 이때에는 비음향 탐지센서인 레이더와 광학, 사람에 의한 시각에 탐지될 확률이 매우 높다. 따라서 본 논문에서는 이러한 상황에서 탐지되는 취약성을 극복하고자 잠수함 마스트 및 잠망경 부분에 비음향 스텔스를 적용하고자 한다. 먼저 비음향 탐지센서에 대해서 조사하고, 그에 따른 스텔스 기법을 분야별 분석하여 최적화한 결과 다층형 구조로 선체표면부터 RAM layer, IR layer, Camouflage layer 구조로 각각 RAM layer는 자성재료인 페라이트계열로 3~5 mm, IR layer는 Ceramic 또는 Nickel 계열로 1~2 mm, Camouflage layer는 군청색 계열 페인팅을 제시하였다. The submarines reach their weakest point when they sail on the surface to operate snorkel and periscope. At this period, however, there lies a high possibility that the submarines are detected by non-acoustic sensors such as radars, IR signatures, and human observations. In this paper, the non-acoustic stealth was adopted on the mast and periscope of submarines so as to overcome their vulnerability of being easily detected in this given situation. First of all, the non-acoustic detection sensors were investigated and the stealth methods were analyzed. And multi-layered structures consisting of RAM layer, IR layer, and Camouflage layer were proposed on the surface of the submarine. As a results, multi-layered structure was suggested with 3~5 mm of a magnetic material such as ferrite for RAM layer, 1~2 mm of ceramic or nickel for IR layer, and sea-blue paint for Camouflage layer.

Effect of hydrogen plasma on growth of Ir thin film by plasma-enhanced hybrid atomic layer deposition

► Growth behaviors of Ir films using hybrid ALD were investigated. ► The 3.2 nm thick Ir film was grown by hybrid ALD under 50 deposition cycles. ► The grown Ir layer exhibited typical self-limited nature of ALD. ► High conformality of 0.88 is achieved on 32 nm wide nano trench. A 3.2-nm-thick Ir layer was grown by a cyclic chemical vapor deposition (CVD)-like hybrid atomic layer deposition (ALD) method on non-patterned Si substrate and a 32-nm-wide TaN-coated nano-trench. Ir metalorganic precursors were mixed with hydrogen reactant and co-fed into the chamber in the same cycle. The Ir metalorganic precursors were effectively decomposed in the gas phase, as in a CVD process, and on the surface of the substrate, as in ALD by hydrogen plasma, which was turned on at feeding time. The nucleation density, which caused a relatively long incubation time, was considerably increased as compared to the conventional ALD process by combining the CVD process with the ALD process. The number of deposition cycles required to obtain a 3.2-nm-thick Ir film on a non-patterned Si substrate was remarkably reduced from 200 to 50 deposition cycles, resulting in a low incubation time. Furthermore, the thickness of the Ir layer increased linearly as the number of deposition cycles increased, which shows the self-limiting nature of typical ALD. The thickness of the Ir layer saturated after 10 s as the precursor injection time was increased, which is further clear evidence of the self-limited nature of ALD. The conformal deposition of Ir was performed on a 32-nm-wide, 3-nm-thick TaN-coated nano trench. The thicknesses of the Ir layer on the top, bottom, left side, and right side were measured to be 3.5, 2.9, 3.3, and 3.4 nm, respectively, as measured by HR-TEM. The calculated conformality was 0.88, which was close to the ideal value without overhang, which often occurs in PVD processes. Our study suggest that this CVD-like hybrid ALD process can be applied to prepare barrier layers with a reduced number of deposition cycles without degradation of the quality of the film, compared to those prepared by the conventional ALD process.

XPS and STEM of the Interface Formation between Ultra-Thin Ru, Ir and Pt Layers and Perylene Red Catalyst Support Whiskers

not Available.

Postnatal day 7 ethanol treatment causes persistent reductions in adult mouse brain volume and cortical neurons with sex specific effects on neurogenesis

Ethanol treatment on postnatal day seven (P7) causes robust brain cell death and is a model of late gestational alcohol exposure (Ikonomidou et al., 2000). To investigate the long-term effects of P7 ethanol treatment on adult brain, mice received either two doses of saline or ethanol on P7 (2.5 g/kg, s.c., 2 h apart) and were assessed as adults (P82) for brain volume (using postmortem MRI) and cellular architecture (using immunohistochemistry). Adult mice that received P7 ethanol had reduced MRI total brain volume (4%) with multiple brain regions being reduced in both males and females. Immunohistochemistry indicated reduced frontal cortical parvalbumin immunoreactive (PV + IR) interneurons (18–33%) and reduced Cux1+IR layer II pyramidal neurons (15%) in both sexes. Interestingly, markers of adult hippocampal neurogenesis differed between sexes, with only ethanol treated males showing increased doublecortin and Ki67 expression (52 and 57% respectively) in the dentate gyrus, consistent with increased neurogenesis compared to controls. These findings suggest that P7 ethanol treatment causes persistent reductions in adult brain volume and frontal cortical neurons in both males and females. Increased adult neurogenesis in males, but not females, is consistent with differential adaptive responses to P7 ethanol toxicity between the sexes. One day of ethanol exposure, e.g. P7, causes persistent adult brain dysmorphology.

Diffusion barrier properties of atomic-layer-deposited iridium thin films on Cu/Ir/Si structures

We investigated the diffusion barrier properties of an atomic-layer-deposited 12-nm-thick iridium (Ir) thin film as functions of the thermal treatment temperature. Up to a temperature of 500 °C, the Ir thin film maintained its initial configuration, preventing the penetration of the Cu layer into Si through the Ir layer. The thermal stability of the Ir layer up to 500 °C was confirmed by using high resolution transmission electron microscopy, Auger electron microscopy, and X-ray diffraction. In contrast, when the Ir layer was thermally annealed at 600 °C, copper silicide was formed, and interdiffusion of Cu and Ir was observed.

Innovative Al–Ni–Ir alloy for bond coats: Microstructure, phase analysis and oxidation behaviour

Iridium modified nickel alluminides are considered promising bond coats due to the capability to promote α-Al 2O 3 scale growth and to develop the formation of Ir layer acting as oxygen diffusion barrier (ODB). An innovative Al–Ni–Ir alloy (Al 60 %at, Ni 35 %at, Ir 5 %at) was formulated, taking into account the bond coat appropriate requirements and the cost standpoint. A detailed and systematic microstructural investigation of both powder and bulk samples was reported, comparing the phase composition, thermal stability and oxidation behaviour of the proposed system with respect to the Ir free one. The analysed AlNiIr system was composed of Al 3Ni 2 and AlNi 3, in addition to the β-NiAl, detected in the reference one. The Ir presence seemed to promote the alumina scale growth, starting at around 1000 °C. Both as cast and oxidised AlNiIr bulk samples showed Ni-poor and Al-rich islands, in which Ir resulted more concentrated, suggesting an iridium higher affinity towards Al with respect to Ni. After the oxidation at operative temperature (i.e. 1150 °C), the α-Al 2O 3 scale growth was observed, increasing the thickness with the dwelling time. Neither Ir ODB nor Ir rich islands at the interface between the alloy and the Al 2O 3 scale were identified, due to the low Ir amount. However the presence of metallic Ir and of the compound Al 2.75Ir was detected in the powder after thermal treatment at 1000 °C.

Coadsorption of CO and O on Ir(1 0 0): First principles calculations

Density functional theory (DFT) calculations with generalized gradient approximation (GGA) are performed to investigate the structural, electronic and energetic properties of Ir(1 0 0)–( mCO+ nO), m=1, 2; n=1, 2 and 3, coadsorption systems. The stability of coadsorbed oxygen is not affected by the increase of CO coverage from 0.25 ML to 0.50 ML. However, the stability of CO increases by increasing O coverage from 0.25 ML to 0.50 ML and 0.75 ML as a result of the rumpling of the topmost Ir layer.

Hydrogen-plasma-assisted hybrid atomic layer deposition of Ir thin film as novel Cu diffusion barrier

We investigated the effect of hydrogen plasma on the growth behavior of Ir thin films using hybrid plasma-enhanced atomic layer deposition (ALD). To increase the rate of adsorption onto the surface of Si substrates, which is considered to be the bottleneck in Ir ALD, hydrogen was co-fed into the chamber with an Ir metalorganic precursor formed by mixing the Ir precursor and reactant species in the same cycle. The hydrogen plasma effectively decomposes the Ir metalorganic precursors, resulting in an increase in the adsorption rate. A uniform, 5-nm-thick Ir thin film was grown on a Si substrate with a sharp interface between the substrate and film in less than 50 deposition cycle. Moreover, the dependence of the thickness on the number of deposition cycles shows a linear relationship, which is characteristic of the self-limiting nature of ALD. Compared with conventional oxygen and ammonia reactants, the process time required to deposit a 5-nm-thick Ir layer was remarkably reduced from 200 to 50cycles by mixing the reactant species with the metal precursor. X-ray diffraction analysis revealed that poly-crystalline Ir was grown with preferential growth in the (111) direction. Our study suggests that the hybrid ALD method can be applied to a mass production line to reduce process time while maintaining the same film quality.

The selective oxidation of ethanol to CO 2 at Pt pc/Ir/Pt metallic multilayer nanostructured electrodes

In this work, Pt pc/Ir/Pt metallic multilayer nanostructured electrodes were prepared. The composition and number of the constituent metal layers were varied and the number of Ir and Pt layers studied were: 1.5:1.5, 1.5:10, 10:1.5, 10:10 and 250:250 Ir and Pt monolayers. The ethanol electrooxidation reaction and its products was studied using electrochemical in situ FTIR technique and could be observed as a selective cleavage of the ethanol C C bond in acidic electrolyte. Neither acetaldehyde nor acetic acid IR band could be observed for ethanol electrooxidation at 1.5 V vs. RHE over Pt pc/Ir 250/Pt 250 metallic multilayer electrodes. Also, the enhancement on CO 2 production over this electrode was more than six times the amount observed using the Pt pc electrodes. Thus, the complete C C cleavage bond in ethanol molecule was observed, leading only CO 2 as reaction product.

Growth Behavior of Iridium on Si Substrates Prepared by Plasma Enhanced Atomic Layer Deposition

Growth behavior of iridium (Ir) thin film on Si substrates prepared by plasma enhanced atomic layer deposition (PEALD) was systematically studied. Ir(EtCp)(COD) and oxygen was employed as a precursor and reactant, respectively. To obtain optimal conditions for depositing nanometer scale Ir thin film, deposition temperature, cycle dependence and precursor feeding time dependence were studied. Uniform 12 nm thick Ir layer with sharp interface was grown at the temperature range of 330-360 degrees C at the fixed deposition cycles of 300. The grown Ir film showed linear properties as a function of deposition cycles which is a typical self-limiting characteristic of ALD. The XRD patterns revealed that IrOx was not formed due to relatively low partial pressure of oxygen. The optimal conditions obtained for 12 nm thick Ir thin film were 330 degrees C of deposition temperature, 300 deposition cycles, and 10 sec of precursor feeding time.

Effect of interface layer on growth behavior of atomic-layer-deposited Ir thin film as novel Cu diffusion barrier

Growth and nucleation behavior of Ir films grown by atomic layer deposition (ALD) on different interfacial layers such as SiO 2, surface-treated TaN, and 3-nm-thick TaN were investigated. To grow Ir thin film by ALD, (1,5-cyclooctadiene) (ethylcyclopentadienyl) iridium (Ir(EtCp)(COD)) and oxygen were employed as the metalorganic precursor and reactant, respectively. To obtain optimal deposition conditions, the deposition temperature was varied from 240 to 420 °C and the number of deposition cycles was changed from 150 to 300. The Ir film grown on the 3-nm-thick TaN surface showed the smoothest and most uniform layer for all the deposition cycles, whereas poor nucleation and three-dimensional island-type growth of the Ir layer were observed on Si, SiO 2, and surface-treated TaN after fewer number of deposition cycles. The uniformity of the Ir film layer was maintained for all the different substrates up to 300 deposition cycles. Therefore we suggest that the growth behavior of the Ir layer on different interface layer is related to the chemical bonding pattern of the substrate film or interface layer, resulting in better understand the growth mechanism of Ir layer as a copper diffusion barrier. The ALD-grown Ir films show the preferential direction of (1 1 1) for all the reflections, which indicates the absence of IrO 2 in metallic Ir.

Plasma-enhanced atomic layer deposition of Ir thin films for copper adhesion layer

The crystallinity of a Cu seed layer and its adhesion to a 3 nm-thick TaN diffusion barrier metal were improved by introducing a 3 nm-thick Ir adhesion layer prepared by plasma-enhanced atomic layer deposition (PEALD) using an alternating supply of (ethylcyclopentadienyl)(1,5-cyclooctadien) iridium [Ir(EtCp)(COD)] and NH 3 plasma at 290 °C. The properties of the Ir adhesion layer were carefully compared with those of a Ru adhesion layer. The surface roughness of the Cu layer deposited on the 3 nm-thick Ir adhesion layer improved significantly compared with the 3 nm-thick Ru adhesion layer. Furthermore, the preferential orientation of Cu (111) on the Ir layer was more enhanced than that on the Ru layer due to the low lattice misfit. Consequently, a 10 nm-thick continuous Cu film with root-mean-squared (RMS) surface roughness of 0.7 nm was successfully prepared on a 3 nm-thick Ir film. Also, the 3 nm-thick Ir layer was found to be sufficient as a Cu adhesion layer.

Heteroepitaxial Ir layers on diamond

Ir layers were deposited on single-crystal diamond using magnetron sputtering at substrate temperatures ranging from 830 to 1150 °C. The grown films have high adhesion to diamond and a low surface roughness Rq = 4–6 nm according to the AFM measurements. Crystalline perfection of Ir layers was investigated using x-ray diffraction and heteroepitaxial growth of Ir on diamond was confirmed. Because the lattice parameters of Ir and diamond are significantly different (7.65%) and because the deposition temperature of Ir is low in comparison with its melting point (2443 °C), diffraction reflections of the films are similar to analogous reflections of diamond, but wider. The films consist of elongated crystallites of length 10–100 nm. By broadening the reciprocal lattice points, we conclude that the level of microstresses in the Ir films increases as the substrate temperature during deposition of Ir films on the (0 0 1) diamond substrate increases, and that the level of microstresses decreases for the films on the (0 1 1) substrate. Simultaneously, the misorientation of Ir crystallites on the (0 1 1) substrate also decreases with increasing temperature.

Iridium/silicon multilayers for extreme ultraviolet applications in the 20–35 nm wavelength range

We have developed an Ir/Si multilayer for extreme ultraviolet (EUV) applications. Normal incidence reflectance measurements of a prototype film tuned to 30 nm wavelength show superior performance relative to a conventional Mo/Si multilayer structure; we also find good stability over time. Transmission electron microscopy and electron dispersive x-ray spectroscopy have been used to examine the microstructure and interface properties of this system: we find amorphous Si layers and polycrystalline Ir layers, with asymmetric interlayer regions of mixed composition. Potential applications of Ir/Si multilayers include instrumentation for solar physics and laboratory EUV beam manipulation.

ENHANCED ELECTROCALORIC PROPERTIES OF PMN-PT THIN FILMS WITH LSCO BUFFER LAYERS

Lead magnesium niobate-lead titanate (PMN-PT) ferroelectric thin films were deposited on Ir/SrTiO3/TiN/Si (001) substrates by oxygen plasma assisted pulsed laser deposition (PLD) method. Effects of the lanthanum strontium cobaltite (LSCO) buffer layer between the PMN-PT film and the Ir layer on the crystallinity, microstructure, ferroelectric properties and electrocaloric effect of the film were investigated. Results show that the LSCO buffer layer can improve the crystallinity and electrocaloric properties effectively. By applying a voltage of 5V to the PMN-PT thin film without the LSCO buffer layer, the changes in the reversible adiabatic temperature measured at room temperature and at 508 K are respectively 0.73 K and 2.13 K, while by introducing a LSCO buffer layer, the corresponding values are increased to 1.41 K and 4.25 K.

Morphological and electrical effect of an ultrathin iridium oxide hole extraction layer on P3HT:PCBM bulk-heterojunction solar cells

An ultrathin iridium layer was treated with O 2-plasma to form an iridium oxide (IrO x ), employed as a hole extraction layer in order to replace poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) in organic photovoltaic (OPV) cells with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The IrO x layer affects the self-organization of the P3HT:PCBM photo-active layer due to its hydrophobic nature, inducing a well-organized intraplane structure with lamellae oriented normal to the substrate. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased by 0.57 eV as the Ir layer on ITO changed to IrO x by the O 2-plasma treatment. The OPV cell with IrO x (2.0 nm) exhibits increased power conversion efficiency as high as 3.5% under 100 mW cm −2 illumination with an air mass (AM 1.5G) condition, higher than that of 3.3% with PEDOT:PSS.

Optical property and thermal stability of Mo/Mo–SiO2/SiO2 solar‐selective coating prepared by magnetron sputtering

AbstractMo/Mo–SiO2/SiO2 solar‐selective coating for high‐temperature solar thermal application is prepared on quartz glass by direct‐current (DC) and radio‐frequency (RF) co‐sputtering. The normal solar absorptance αn = 0.95 and thermal emittance εn = 0.097 (353 K) are obtained through process optimization. The normal reflectance Rn(λ) before and after 1073 K vacuum annealing, are measured by ultraviolet–visible–infrared (UV–VIS–IR) and Fourier transform infrared (FT‐IR) spectroscopy. There is only a slight increase in Rn(λ) in IR region after annealing, which results in a lower εn = 0.075 (353 K). The crystallized grain of Mo in the coating, obtained from XRD pattern, increased from 23 to 60 nm after vacuum annealing. These phenomena are mainly caused by the change of crystal state and reflectance of Mo IR layer according to the comparison of Rn(λ) and XRD patterns of Mo/SiO2 and Mo–SiO2/SiO2 tandem films.magnified image The near‐normal reflectance of Mo/Mo–SiO2/SiO2 solar‐selective coating before and after 1073 K vacuum annealing.

Efficient Förster energy transfer from phosphorescent organic molecules to J-aggregate thin films

Abstract We demonstrate efficient Forster resonance energy transfer (FRET) from a thin film of phosphorescent dye, fac tris(2-phenylpyridine) iridium (Ir(ppy)3), to a thin film of J-aggregated cyanine dye, 5,6-dichloro-2-[3-[5,6-dichloro-1-ethyl-3-(3-sulfopropyl)-2(3H)-benzimidazolidene]-1-propenyl]-1-ethyl-3-(3-sulfopropyl) benzimidazolium hydroxide (TDBC). The measurement is performed on a planar sandwich structure with the layer of Ir(ppy)3 and the layer of J-aggregates separated by a uniform optically inert spacer layer. Quenching of Ir(ppy)3 photoluminescence due to FRET of Ir(ppy)3 excitons to J-aggregates enables us to calculate the experimentally-determined Forster radius of 3.8 nm, which is in good agreement with the theoretically calculated value.

Application of textured IBAD-TiN buffer layers in coated conductor architectures

Ion-beam assisted deposition (IBAD) is one of the major techniques for preparing highly textured templatesfor YBa2Cu3O7−x (YBCO) coated conductors. In most applications so far IBAD-MgO has beenused. TiN is an alternative material for the IBAD process showing a texturednucleation similar to MgO. Different amorphous or nanocrystalline seed layers such asAl2O3,Y2O3 orTa0.75Ni0.25 were found to be suitable for achieving strong cube textures in film thicknessesbelow 10 nm using reactive ion-beam assisted pulsed laser deposition. The biaxialtexture was preserved to a higher thickness using homoepitaxial growth athigher temperatures. Different buffer layer architectures based on IBAD-TiNhave been developed on Hastelloy substrates. An electrically conducting bufferlayer stack was realized using a double layer of Au and Ir with a final Nb-dopedSrTiO3 cap layer, enabling the epitaxial growth of YBCO on top.Alternatively, a robust simplified buffer architecture was studied usingSrZrO3 directly on TiN, leading to highly textured YBCO layers.

RDE Measurements of ORR Activity of Pt1 − xIrx ( 0 < x < 0.3 ) on High Surface Area NSTF-Coated Glassy Carbon Disks

Layered and Pt films were sputtered onto mirror-polished and nanostructured thin film (NSTF)-coated glassy carbon (GC) disks. Rotating disk electrode (RDE) studies of oxygen reduction reaction (ORR) activity were completed for all prepared disks. The film was prepared by depositing alternating layers of Pt (constant thickness) and Ir (gradient), finished with a Pt top layer. The NSTF-supported catalysts had much higher active surface areas and reached the diffusion-limited current at higher potentials than the bare GC supported catalysts. The surface enhancement factor (SEF) of Pt on NSTF-coated disks was approximately 14. The SEF increased (reaching a maximum of 22 at in ) as the Ir content increased for the samples on NSTF. The kinetic ORR current density also increased with increasing Ir content. A similar trend was not observed for the same catalyst coated onto bare GC disks. All of the catalyst/support combinations had identical Tafel slopes and area-specific current densities, suggesting that Pt is the active catalytic ingredient. Catalysts coated on NSTF-coated GC disks can be used to accurately examine both catalytic activities and the effects of high surface area supports in a single measurement.