Two-Step Electrochemical Au Nanoparticle Formation in Polyaniline.

In this work, we use a two-step cyclic electrochemical process to insert Au into polyaniline (PANI). It was suggested previously that this method would lead to the formation of atomic Au clusters with controlleds number of Au atoms without providing morphological proof. In each cycle, tetrachloroaurate anions (AuCl4-) are attached on the protonated imine sites of PANI, followed by a controlled reduction using cyclic voltammetry (CV). In contrast to previous work, we demonstrate that the reduction leads to the nucleation and growth of an Au nanoparticle (NP) whose density and size dispersion depend on the Au loading in PANI. Adding more deposition cycles increases the Au NP density and size. Transmission electron microscopy (TEM) and corresponding energy dispersive X-ray spectroscopy (EDS) indicate a homogeneous distribution of Au elements in the PANI matrix before CV reduction, while Au elements are aggregated and clearly localized in the NPs positions after CV reduction. We further use Rutherford backscattering spectrometry (RBS) to quantify the Au uptake in PANI. The Au distribution is verified to be initially homogeneous across the PANI layer whereas the increasing number of deposition cycles leads to a surface segregation of Au. We propose a two-step growth model based on our experimental results. Finally, we discuss the results with respect to the formation of atomic Au clusters reported previously using the same deposition method.

Amphiphilic Alginate-Based Layer-by-Layer Coatings Exhibiting Resistance against Nonspecific Protein Adsorption and Marine Biofouling.

Amphiphilic coatings are promising materials for fouling-release applications, especially when their building blocks are inexpensive, biodegradable, and readily accessible polysaccharides. Here, amphiphilic polysaccharides were fabricated by coupling hydrophobic pentafluoropropylamine (PFPA) to carboxylate groups of hydrophilic alginic acid, a natural biopolymer with high water-binding capacity. Layer-by-layer (LbL) coatings comprising unmodified or amphiphilic alginic acid (AA*) and polyethylenimine (PEI) were assembled to explore how different PFPA contents affect their physicochemical properties, resistance against nonspecific adsorption (NSA) of proteins, and antifouling activity against marine bacteria (Cobetia marina) and diatoms (Navicula perminuta). The amphiphilic multilayers, characterized through spectroscopic ellipsometry, water contact angle goniometry, elemental analysis, AFM, XPS, and SPR spectroscopy, showed similar or even higher swelling in water and exhibited higher resistance toward NSA of proteins and microfouling marine organisms than multilayers without fluoroalkyl groups.

Microscopic Diffusion of Atomic Hydrogen and Water in HER Catalyst MoS2 Revealed by Neutron Scattering.

The design of novel and abundant catalytic materials for electrolysis is crucial for reaching carbon neutrality of the global energy system. A deliberate approach to catalyst design requires both theoretical and experimental knowledge not only of the target reactions but also of the supplementary mechanisms affecting the catalytic activity. In this study, we focus on the interplay of hydrogen mobility and reactivity in the hydrogen evolution reaction catalyst MoS2. We have studied the diffusion of atomic hydrogen and water by means of neutron and X-ray photoelectron spectroscopies combined with classical molecular dynamics simulations. The observed interaction of water with single-crystal MoS2 shows the possibility of intercalation within volume defects, where it can access edge sites of the material. Our surface studies also demonstrate that atomic hydrogen can be inserted into MoS2, where it then occupies various adsorption sites, possibly favoring defect vicinities. The motion of H atoms parallel to the layers of MoS2 is fast with D ≈ 1 × 10-9 m2/s at room temperature and exhibits Brownian diffusion behavior with little dependence on temperature, i.e., with a very low diffusion activation barrier.

Effect of Multilayer Termination on Nonspecific Protein Adsorption and Antifouling Activity of Alginate-Based Layer-by-Layer Coatings.

Layer-by-layer (LbL) assembly is a versatile platform for applying coatings and studying the properties of promising compounds for antifouling applications. Here, alginate-based LbL coatings were fabricated by alternating the deposition of alginic acid and chitosan or polyethylenimine to form multilayer coatings. Films were prepared with either odd or even bilayer numbers to investigate if the termination of the LbL coatings affects the physicochemical properties, resistance against the nonspecific adsorption (NSA) of proteins, and antifouling efficacy. The hydrophilic films, which were characterized using spectroscopic ellipsometry, water contact angle goniometry, ATR-FTIR spectroscopy, AFM, XPS, and SPR spectroscopy, revealed high swelling in water and strongly reduced the NSA of proteins compared to the hydrophobic reference. While the choice of the polycation was important for the protein resistance of the LbL coatings, the termination mattered less. The attachment of diatoms and settling of barnacle cypris larvae revealed good antifouling properties that were controlled by the termination and the charge density of the LbL films.

Structural degradation of tungsten sandwiched in hafnia layers determined by in-situ XRD up to 1520 °C.

The high-temperature stability of thermal emitters is one of the critical properties of thermophotovoltaic (TPV) systems to obtain high radiative power and conversion efficiencies. W and HfO2 are ideal due to their high melting points and low vapor pressures. At high temperatures and given vacuum conditions, W is prone to oxidation resulting in instantaneous sublimation of volatile W oxides. Herein, we present a detailed in-situ XRD analysis of the morphological changes of a 3-layer-system: HfO2/W/HfO2 layers, in a high-temperature environment, up to 1520 °C. These samples were annealed between 300 °C and 1520 °C for 6 h, 20 h, and 40 h at a vacuum pressure below 3 × 10-6 mbar using an in-situ high-temperature X-ray diffractometer, which allows investigation of crucial alterations in HfO2 and W layers. HfO2 exhibits polymorphic behavior, phase transformations and anisotropy of thermal expansion leads to formation of voids above 800 °C. These voids serve as transport channels for the residual O2 present in the annealing chamber to access W, react with it and form volatile tungsten oxides. An activation energy of 1.2 eV is calculated. This study clarifies the limits for the operation of W-HfO2 spectrally selective emitters for TPV in high-temperature applications.

Neutron spectroscopy study of the diffusivity of hydrogen in MoS2.

The diffusion of hydrogen adsorbed inside layered MoS2 crystals has been studied by means of quasi-elastic neutron scattering, neutron spin-echo spectroscopy, nuclear reaction analysis, and X-ray photoelectron spectroscopy. The neutron time-of-flight and neutron spin-echo measurements demonstrate fast diffusion of hydrogen molecules parallel to the basal planes of the two dimensional crystal planes. At room temperature and above, this intra-layer diffusion is of a similar speed to the surface diffusion that has been observed in earlier studies for hydrogen atoms on Pt surfaces. A significantly slower hydrogen diffusion was observed perpendicular to the basal planes using nuclear reaction analysis.

Investigating Zinc Ketoiminates as a New Class of Precursors for Solution Deposition of ZnO Thin Films.

Zinc oxide (ZnO) has been recognized as one of the most promising metal oxide semiconductor material for processing low-cost thin film transistors (TFTs). Within the scope of this work, we demonstrate a simple, stabilizer free and very efficient chemical solution deposition (CSD) route to grow high quality ZnO layers. The identification of a highly soluble zinc ketoiminate precursor that undergoes hydrolysis under ambient conditions with the facile cleavage of the ligands was the key to develop a simple and straightforward process for ZnO thin films under mild process conditions. Upon heat treatment at moderate temperatures, the precursor decomposes cleanly yielding polycrystalline ZnO thin films, which was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composition was investigated employing complementary techniques such as X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) which revealed high purity ZnO layers. The functional properties in terms of transparency and optical band gap were determined by ultraviolet-visible (UV-Vis) spectroscopy. The transparent ZnO semiconductor thin films serve as active channel layer of thin film transistors (TFT) which was demonstrated by spin coating of the precursor. Subsequent curing in ambient air, yields a 10 nm film that is sufficient to fabricate working TFTs test structures.

Amphiphilic Alginates for Marine Antifouling Applications.

Amphiphilic polymers are promising candidates for novel fouling-release coatings for marine applications. We grafted amphiphilic alginates with fluorinated side chains to glass and silicon substrates and characterized the obtained films by contact angle goniometry, spectroscopic ellipsometry, XPS, and ATR-FTIR. The potential to inhibit protein attachment was tested against four different proteins, and intermediate fluorine loadings showed the strongest reduction with respect to hydrophobic, aliphatic controls. A similar trend was observed in dynamic attachment experiments using Navicula perminuta diatoms and settlement experiments with zoospores of the green algae Ulva linza. The results indicate that amphiphilic alginates are promising natural and renewable biomacromolecules that could be included in future protective coating technologies.

Low temperature growth of gallium oxide thin films via plasma enhanced atomic layer deposition.

Herein we describe an efficient low temperature (60-160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (Ga2O3) thin films using hexakis(dimethylamido)digallium [Ga(NMe2)3]2 with oxygen (O2) plasma on Si(100). The use of O2 plasma was found to have a significant improvement on the growth rate and deposition temperature when compared to former Ga2O3 processes. The process yielded the second highest growth rates (1.5 Å per cycle) in terms of Ga2O3 ALD and the lowest temperature to date for the ALD growth of Ga2O3 and typical ALD characteristics were determined. From in situ quartz crystal microbalance (QCM) studies and ex situ ellipsometry measurements, it was deduced that the process is initially substrate-inhibited. Complementary analytical techniques were employed to investigate the crystallinity (grazing-incidence X-ray diffraction), composition (Rutherford backscattering analysis/nuclear reaction analysis/X-ray photoelectron spectroscopy), morphology (X-ray reflectivity/atomic force microscopy) which revealed the formation of amorphous, homogeneous and nearly stoichiometric Ga2O3 thin films of high purity (carbon and nitrogen <2 at.%) under optimised process conditions. Tauc plots obtained via UV-Vis spectroscopy yielded a band gap of 4.9 eV and the transmittance values were more than 80%. Upon annealing at 1000 °C, the transformation to oxygen rich polycrystalline ß-gallium oxide took place, which also resulted in the densification and roughening of the layer, accompanied by a slight reduction in the band gap. This work outlines a fast and efficient method for the low temperature ALD growth of Ga2O3 thin films and provides the means to deposit Ga2O3 upon thermally sensitive polymers like polyethylene terephthalate.

Integrating AlN with GdN Thin Films in an in Situ CVD Process: Influence on the Oxidation and Crystallinity of GdN.

The application potential of rare earth nitride (REN) materials has been limited due to their high sensitivity to air and moisture leading to facile oxidation upon exposure to ambient conditions. For the growth of device quality films, physical vapor deposition methods, such as molecular beam epitaxy, have been established in the past. In this regard, aluminum nitride (AlN) has been employed as a capping layer to protect the functional gadolinium nitride (GdN) from interaction with the atmosphere. In addition, an AlN buffer was employed between a silicon substrate and GdN serving as a seeding layer for epitaxial growth. In pursuit to grow high-quality GdN thin films by chemical vapor deposition (CVD), this successful concept is transferred to an in situ CVD process. Thereby, AlN thin films are included step-wise in the stack starting with Si/GdN/AlN structures to realize long-term stability of the oxophilic GdN layer. As a second strategy, a Si/AlN/GdN/AlN stacked structure was grown, where the additional buffer layer serves as the seeding layer to promote crystalline GdN growth. In addition, chemical interaction between GdN and the Si substrate can be prevented by spatial segregation. The stacked structures grown for the first time with a continuous CVD process were subjected to a detailed investigation in terms of structure, morphology, and composition, revealing an improved GdN purity with respect to earlier grown CVD thin films. Employing thin AlN buffer layers, the crystallinity of the GdN films on Si(100) could additionally be significantly enhanced. Finally, the magnetic properties of the fabricated stacks were evaluated by performing superconducting quantum interference device measurements, both of the as-deposited films and after exposure to ambient conditions, suggesting superparamagnetism of ferromagnetic GdN grains. The consistency of the magnetic properties precludes oxidation of the REN material due to the amorphous AlN capping layer.

Synthesis and evaluation of new copper ketoiminate precursors for a facile and additive-free solution-based approach to nanoscale copper oxide thin films.

Novel copper ketoiminate compounds were synthesized and for the first time applied for additive-free solution-based deposition of nanoscale copper oxide thin films. The two closely related compounds, namely the bis[4-(2-ethoxyethyl-imino)-3-pentanonato]copper, [Cu(EEKI)2], and bis[4-(3-methoxypropylimino)-3-pentanonato]copper, [Cu(MPKI)2], were characterized by means of elemental and thermogravimetric analysis (TGA), as well as electron impact mass spectrometry (EI-MS). The advantages of these compounds are that they are liquid and possess excellent solubility in common organic solvents in addition to an optimum reactivity towards ambient moisture that enables a facile solution-based approach to nanoscale copper oxide thin films. Moreover, no additives or aging is needed to stabilize the solution processing of the copper oxide layers. [Cu(MPKI)2] was tested in detail for the deposition of copper oxide thin films by spin coating. Upon one-step annealing, high-quality, uniform, crystalline copper oxide thin films were deposited on Si, SiO2, as well as on quartz substrates. Structural, morphological and compositional characteristics of the copper oxide nanostructures were investigated in detail by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and a combined analysis using Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). It was possible to control the copper oxide phases (CuO and Cu2O) by systematic tuning of the post-deposition annealing conditions. The functional properties in terms of optical band gap were investigated using UV/Vis spectroscopy, while the transport properties, such as resistivity, mobility and carrier concentration were analyzed employing Hall measurements, which confirmed the p-type conductivity of the copper oxide layers.

Systematic molecular engineering of Zn-ketoiminates for application as precursors in atomic layer depositions of zinc oxide.

Molecular engineering of seven closely related zinc ketoiminates, namely, [Zn(dapki)2], [Zn(daeki)2], [Zn(epki)2], [Zn(eeki)2], [Zn(mpki)2], [Zn(meki)2], and [Zn(npki)2], leads to the optimisation of precursor thermal properties in terms of volatilisation rate, onset of volatilisation, reactivity and thermal stability. The influence of functional groups at the imine side chain of the ligands on the precursor properties is studied with regard to their viability as precursors for atomic layer deposition (ALD) of ZnO. The synthesis of [Zn(eeki)2], [Zn(epki)2] and [Zn(dapki)2] and the crystal structures of [Zn(mpki)2], [Zn(eeki)2], [Zn(dapki)2] and [Zn(npki)2] are presented. From the investigation of the physico-chemical characteristics, it was inferred that all compounds are monomeric, volatile and exhibit high thermal stability, all of which make them promising ALD precursors. Compound [Zn(eeki)2] is in terms of thermal properties the most promising Zn-ketoiminate. It is reactive towards water, possesses a melting point of 39 °C, is stable up to 24 days at 220 °C and has an extended volatilisation rate compared to the literature known Zn-ketoiminates. It demonstrated self-saturated, water assisted growth of zinc oxide (ZnO) with growth rates in the order of 1.3 Å per cycle. Moreover, it displayed a broad temperature window from TDep = 175-300 °C and is the first report of a stable high temperature (>200 °C) ALD process for ZnO returning highly promising growth rates.

Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors.

The nuclear spins of ionized donors in silicon have become an interesting quantum resource due to their very long coherence times. Their perfect isolation, however, comes at a price, since the absence of the donor electron makes the nuclear spin difficult to control. We demonstrate that the quadrupolar interaction allows us to effectively tune the nuclear magnetic resonance of ionized arsenic donors in silicon via strain and determine the two nonzero elements of the S tensor linking strain and electric field gradients in this material to S(11)=1.5×10(22) V/m2 and S(44)=6×10(22) V/m2. We find a stronger benefit of dynamical decoupling on the coherence properties of transitions subject to first-order quadrupole shifts than on those subject to only second-order shifts and discuss applications of quadrupole physics including mechanical driving of magnetic resonance, cooling of mechanical resonators, and strain-mediated spin coupling.

Novel ß-ketoiminato complexes of zirconium: synthesis, characterization and evaluation for solution based processing of ZrO2 thin films.

Treatment of tetrakis(diethylamido)zirconium(IV); [Zr(NEt2)4] with a series of ß-ketoimines ({[RHN]C(CH3)=C(H)C(CH3)=O} where R is a functionalized side-chain; 4-(2-methoxyethylamino)pent-3-en-2-one, Hmeap; 4-(3-methoxypropylamino)pent-3-en-2-one, Hmpap; 4-(2-(dimethylamino)ethylamino)pent-3-en-2-one, Hdeap; 4-(3-(dimethylamino)propylamino)pent-3-en-2-one, Hdpap) leads to an amine substitution reaction that yielded novel monomeric heteroleptic mixed amido-ketoiminato complexes of the type bis(4-(2-methoxyethylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (1), bis(4-(3-methoxypropylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (2), and bis(4-(3-(dimethylamino)propylamino)pent-3-en-2-onato)bis(diethylamido)zirconium(IV) (3), and eight-coordinated homoleptic complexes tetrakis(4-(2-methoxyethylamino)pent-3-en-2-onato)zirconium(IV) (4) and tetrakis(4-(2-(dimethylamino)ethylamino)pent-3-en-2-onato)zirconium(IV) (5), depending on the ratio of the ligand to zirconium. Adopting a similar strategy with zirconium alkoxide, namely [Zr(O(i)Pr)4·(i)PrOH], with ß-ketoimine Hmeap, leads to the formation of a dimer, bis(µ2-isopropoxo)bis(4-(2-methoxyethylamino)pent-3-en-2-onato)tetrakis(isopropoxo)dizirconium(IV) (6). The newly synthesised complexes were characterized by NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, elemental analysis and thermal analysis. The low decomposition temperature facilitated by the stepwise elimination of the ketominate ligand from the complex and the stability of the complexes obtained in air as well as in solution makes them highly suitable for solution based processing of ZrO2 thin films, which is demonstrated using compound 5 on Si(100) substrates. High quality ZrO2 films were obtained and were investigated for their structure, morphology, composition and optical properties. Low temperature crystallisation of ZrO2 is achieved by a simple chemical deposition process using the new class of Zr precursors and the films exhibit an optical transmittance above 90%.

High-throughput compositional and structural evaluation of a Li(a)(Ni(x)Mn(y)Co(z))O(r) thin film battery materials library.

A Lia(NixMnyCoz)Or cathode materials library was fabricated by combinatorial magnetron sputtering. The compositional analysis of the library was performed by a new high-throughput approach for Li-content measurement in thin films, which combines automated energy-dispersive X-ray spectroscopy, Deuteron-induced gamma emission, and Rutherford backscattering measurements. Furthermore, combining this approach with thickness measurements allows the mapping of density values of samples from the materials library. By correlating the obtained compositional data with structural data from high-throughput X-ray diffraction measurements, those compositions which show a layered (R3̅m) structure and are therefore most interesting for Li-battery applications (for cathode (positive) electrodes) can be rapidly identified. This structure was identified as being most pronounced in the compositions Li0.6(Ni0.16Mn0.35Co0.48)O2, Li0.7(Ni0.10Mn0.37Co0.51)O2, Li0.6(Ni0.23Mn0.33Co0.43)O2, Li0.3(Ni0.65Mn0.08Co0.26)O2, Li0.3(Ni0.63Mn0.08Co0.29)O2, Li0.4(Ni0.56Mn0.09Co0.34)O2, Li0.5(Ni0.45Mn0.13Co0.42)O2, and Li0.6(Ni0.34Mn0.14Co0.52)O2.

Homoleptic gadolinium amidinates as precursors for MOCVD of oriented gadolinium nitride (GdN) thin films.

Five new homoleptic gadolinium tris-amidinate complexes are reported, which were synthesized via the salt-elimination reaction of GdCl(3) with 3 equiv of lithiated symmetric and asymmetric amidinates at ambient temperature. The Gd-tris-amidinates [Gd{(N(i)Pr)(2)CR}(3)] [R = Me (1), Et (2), (t)Bu (3), (n)Bu (4)] and [Gd{(NEt)(N(t)Bu)CMe}(3)] (5) are solids at room temperature and sublime at temperatures of about 125 °C (6 × 10(-2) mbar) with the exception of compound 4, which is a viscous liquid at room temperature. According to X-ray diffraction analysis of 3 and 5 as representative examples of the series, the complexes adopt a distorted octahedral structure in the solid state. Mass spectrometric (MS) data confirmed the monomeric structure in the gas phase, and high-resolution MS allowed the identification of characteristic fragments, such as [{(N(i)Pr)(2)CR}GdCH(3)](+) and [{(N(i)Pr)(2)CR}GdNH](+). The alkyl substitution patterns of the amidinate ligands clearly show an influence on the thermal properties, and specifically, the introduction of the asymmetric carbodiimide leads to a lowering of the onset of volatilization and decomposition. Compound 5, which is the first Gd complex with an asymmetric amidinate ligand system to be reported, was, therefore, tested for the MOCVD of GdN thin films. The as-deposited GdN films were capped with Cu in a subsequent MOCVD process to prevent postdeposition oxidation of the films. Cubic GdN on Si(100) substrates with a preferred orientation in the (200) direction were grown at 750 °C under an ammonia atmosphere and exhibited a columnar morphology and low levels of C or O impurities according to scanning electron microscopy, Rutherford backscattering, and nuclear reaction analysis.

Sc2O3, Er2O3, and Y2O3 thin films by MOCVD from volatile guanidinate class of rare-earth precursors.

Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)(3)] (1), tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)(3)] (2) and tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)(3)] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films, respectively, by metal-organic chemical vapor deposition (MOCVD). Uniform Sc(2)O(3), Er(2)O(3) and Y(2)O(3) films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350-700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1-3 are very good precursors for MOCVD yielding Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.

Atomic vapor deposition approach to In2O3 thin films.

In2O3 thin films were grown by atomic vapor deposition (AVD) on Si(100) and glass substrates from a tris-guanidinate complex of indium [In(N(i)Pr2guanid)3] under an oxygen atmosphere. The effects of the growth temperature on the structure, morphology and composition of In2O3 films were investigated. X-ray diffraction (XRD) measurements revealed that In2O3 films deposited in the temperature range 450-700 degreesC crystallised in the cubic phase. The film morphology, studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), was strongly dependent on the substrate temperature. Stoichiometric In2O3 films were formed under optimised processing conditions as was confirmed by X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), as well as by Rutherford backscattering spectrometry (RBS). Finally, optical properties were investigated by photoluminescence (PL) measurements, spectroscopic ellipsometry (SE) and optical absorption. In2O3 films grown on glass exhibited excellent transparency (approximately 90%) in the Visible (Vis) spectral region.

Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt.

Malonate complexes of dysprosium: synthesis, characterization and application for LI-MOCVD of dysprosium containing thin films.

A series of malonate complexes of dysprosium were synthesized as potential metalorganic precursors for Dy containing oxide thin films using chemical vapor deposition (CVD) related techniques. The steric bulkiness of the dialkylmalonato ligand employed was systematically varied and its influence on the resulting structural and physico-chemical properties that is relevant for MOCVD was studied. Single crystal X-ray diffraction analysis revealed that the five homoleptic tris-malonato Dy complexes (1-5) are dimers with distorted square-face bicapped trigonal-prismatic geometry and a coordination number of eight. In an attempt to decrease the nuclearity and increase the solubility of the complexes in various solvents, the focus was to react these dimeric complexes with Lewis bases such as 2,2'-biypridyl and pyridine (6-9). This resulted in monomeric tris-malonato mono Lewis base adduct complexes with improved thermal properties. Finally considering the ease of synthesis, the monomeric nature and promising thermal characteristics, the silymalonate adduct complex [Dy(dsml)(3)bipy] (8) was selected as single source precursor for growing DySi(x)O(y) thin films by liquid injection metalorganic chemical vapor deposition (LI-MOCVD) process. The as-deposited films were analyzed for their morphology and composition by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Rutherford backscattering (RBS) analysis and X-ray photoelectron spectroscopy.