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Atomic Layer Deposition (atomic + layer_deposition)
Selected AbstractsAtomic Layer Deposition of High- k Oxides of the Group 4 Metals for Memory Applications (Adv. Eng.ADVANCED ENGINEERING MATERIALS, Issue 4 2009Mater. The cover shows high temperature XRD patterns of a 5.8 nm thick HfO2 film and 7.3 nm yttrium-doped HfO2 grown by atomic layer deposition (ALD). More details can be found in the article of J. Niinistö et al. where recent development in ALD of high-k dielectric oxides for memory applications is reviewed on page 223. [source] Atomic Layer Deposition of High- k Oxides of the Group 4 Metals for Memory Applications,ADVANCED ENGINEERING MATERIALS, Issue 4 2009Jaakko Niinistö Abstract This paper reviews several high-k ALD processes potentially applicable to the production of capacitors, concentrating on very recent developments. A list of the dielectric materials under investigation consists of the oxides of several metals, including the Group 4 (Ti, Zr, Hf) elements. The binary oxides of Group 4 metals, as well as their mixtures with other oxides, doped hosts, or multi-layers in the form of nano-laminates are of interest.Several examples of our recent results are shown, including possible ALD routes to materials not previously grown, as well as advances in process development. [source] Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer DepositionADVANCED FUNCTIONAL MATERIALS, Issue 18 2010David J. Comstock Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source] Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer DepositionADVANCED FUNCTIONAL MATERIALS, Issue 18 2010David J. Comstock Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source] Atomic Layer Deposition of UV-Absorbing ZnO Films on SiO2 and TiO2 Nanoparticles Using a Fluidized Bed Reactor,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2008David M. King Atomic layer deposition (ALD) was used to apply conformal, nanothick ZnO coatings on particle substrates using a fluidized bed reactor. Diethylzinc (DEZ) and water were used as precursors at 177,°C. Observed growth rates were ca. 2.0 Å/cycle on primary particles as verified by HRTEM. ICP-AES and XPS were used to quantify Zn:substrate ratios. Layers of 6, 18, and 30 nm were deposited on 550 nm SiO2 spheres for UV blocking cosmetics particles. TiO2 nanoparticles were coated in the second part of this work by ZnO shells of 2, 5, and 10 nm thickness as novel inorganic sunscreen particles. The specific surface area of powders changed appropriately after nanothick film deposition using optimized conditions, signifying that high SA particles can be functionalized without agglomeration. The ZnO layers were polycrystalline as deposited and narrowing of the FWHM occurred upon annealing. Annealing the ZnO-TiO2 nanocomposite powder to 600,°C caused the formation of zinc titanate (Zn2TiO4) in both oxygen-rich and oxygen-deficient environments. The non-ideal surface behavior of the DEZ precursor became problematic for the much longer times required for high surface area nanoparticle processing and results in Zn-rich films at this growth temperature. In situ mass spectrometry provides process control capability to functionalize bulk quantities of nano- and ultrafine particles without significant precursor waste or process overruns. ZnO overlayers can be efficiently deposited on the surfaces of primary particles using ALD processing in a scalable fluidized bed reactor. [source] Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007F. Hakim Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source] Effect of an Ultrathin TiO2 Layer Coated on Submicrometer-Sized ZnO Nanocrystallite Aggregates by Atomic Layer Deposition on the Performance of Dye-Sensitized Solar CellsADVANCED MATERIALS, Issue 21 2010Kwangsuk Park An ultrathin TiO2 layer is successfully coated on the surface of sub-m-sized aggregates of ZnO nanocrystallites through the atomic layer deposition (ALD) technique. The ZnO core/TiO2 shell structure increases the open-circuit voltage, without impairing the photocurrent density and results in an increased power conversion efficiency from 5.2% to 6.3%. [source] Ultrathin Direct Atomic Layer Deposition on Composite Electrodes for Highly Durable and Safe Li-Ion BatteriesADVANCED MATERIALS, Issue 19 2010Yoon Seok Jung Direct atomic layer deposition (ALD) on composite electrodes leads to ultrathin conformal protective coatings without disrupting inter-particle electronic pathways. Al2O3 -coated natural graphite (NG) electrodes obtained by direct ALD on the as-formed electrode show exceptionally durable capacity retention even at an elevated temperature of 50,°C. In sharp contrast, ALD on powder results in poorer cycle retention than bare NG. [source] Atomic Layer Deposition of ZnO in Quantum Dot Thin Films,ADVANCED MATERIALS, Issue 2 2009Alexandre Pourret CdSeS/CdS/ZnS quantum dot thin films subjected to ZnO atomic layer deposition at 100°C shows photoluminescence (PL) modulation. The PL is quenched during each exposure to diethyl zinc. However, the PL is restored upon subsequent exposure to water. [source] Synthesis and Surface Engineering of Complex Nanostructures by Atomic Layer Deposition,ADVANCED MATERIALS, Issue 21 2007M. Knez Abstract Atomic layer deposition (ALD) has recently become the method of choice for the semiconductor industry to conformally process extremely thin insulating layers (high- k oxides) onto large-area silicon substrates. ALD is also a key technology for the surface modification of complex nanostructured materials. After briefly introducing ALD, this Review will focus on the various aspects of nanomaterials and their processing by ALD, including nanopores, nanowires and -tubes, nanopatterning and nanolaminates as well as low-temperature ALD for organic nanostructures and biomaterials. Finally, selected examples will be given of device applications, illustrating recent innovative approaches of how ALD can be used in nanotechnology. [source] Hollow Inorganic Nanospheres and Nanotubes with Tunable Wall Thicknesses by Atomic Layer Deposition on Self-Assembled Polymeric Templates,ADVANCED MATERIALS, Issue 1 2007The construction of inorganic nanostructures with hollow interiors is demonstrated by coating self-assembled polymeric nano-objects with a thin Al2O3 layer by atomic layer deposition (ALD), followed by removal of the polymer template upon heating. The morphology of the nano-object (i.e., spherical or cylindrical) is controlled by the block lengths of the copolymer. The thickness of the Al2O3 wall is controlled by the number of ALD cycles. [source] Infiltration and Inversion of Holographically Defined Polymer Photonic Crystal Templates by Atomic Layer Deposition,ADVANCED MATERIALS, Issue 12 2006S. King Practical methods of microfabrication are vital for the development of photonic-crystal-based signal processing. However, extension of the optical methods that dominate integrated circuit fabrication to three dimensions is challenging. This communication reports an essential step for creation of devices operating within a full photonic band gap: atomic layer deposition is used to create the high-index TiO2 replicas of holographically defined photonic crystals shown in the figure. [source] A micron-sized nanoporous multifunction sensing devicePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2009L. Moreno i Codinachs Abstract In this work, a capacitive sensor based on Anodic Aluminium Oxide (AAO) porous structures has been developed. In some cases, the pores have been also conformally coated with a high chemical pure SiO2 by means of Atomic Layer Deposition (ALD). Temperature measurements have been done in DI water obtaining a response of 5 nF/°C. pH measurements have been performed and the responses obtained are between 0.2 and 1 nF/pH. The reproducibility of the sensors has been found to be high and a larger hysteresis effect has been observed in the samples with alumina pores rather than in the SiO2 ones. The hysteresis seems to be related to the charging of the oxide upon application of a voltage. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interface of atomic layer deposited Al2O3 on H-terminated siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2006K. Y. Gao Abstract Al2O3 films 1 to 20 nm thick were deposited as alternative high-, gate dielectric on hydrogen-terminated silicon by Atomic Layer Deposition (ALD) and characterized by Synchrotron X-ray Photoelectron Spec-troscopy (SXPS), Fourier Transform Infrared (FTIR) absorption spectroscopy and admittance measure-ments. The SXPS results indicate that about 60% of the original Si,H surface bonds are preserved at the Al2O3/Si interface and this is confirmed by monitoring the Si,H stretching modes by FTIR spectroscopy in the Attenuated Total Reflection (ATR) mode both before and after ALD of Al2O3. The remaining 40% of Si,H bonds are replaced by Si,O bonds as verified by SXPS. In addition, a fraction of a monolayer of SiO2 forms on top of the Al2O3 dielectric during deposition. The presence of OH-groups at a level of 3% of the total oxygen content was detected throughout the Al2O3 layer through a chemically shifted O 1s component in SXPS. Admittance measurements give a dielectric constant of 9.12, but a relatively high density of interface traps between 1011 and 1012 cm,2 eV,1. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Plasma-Assisted Atomic Layer Deposition of Al2O3 at Room TemperaturePLASMA PROCESSES AND POLYMERS, Issue S1 2009Tommi O. Kääriäinen Abstract A new design of plasma source has been used for the plasma-assisted atomic layer deposition (PA-ALD) of Al2O3 films at room temperature. In this PA-ALD reactor the plasma is generated by capacitive coupling directly in the deposition chamber adjacent to the substrate but can be separated from it by a grid to reduce the ion bombardment while maintaining the flow of radicals directly to the substrate surface. During the ALD cycle a mixture of nitrogen and argon was introduced into the reactor to act as a purge gas between precursor pulses and to facilitate the generation of a plasma during the plasma cycle. Sequential exposures of TMA and excited O2 precursors were used to deposit Al2O3 films on Si(100) substrates. A plasma discharge was activated during the oxygen gas pulse to form radicals in the reactor space. The experiments showed that the growth rate of the film increased with increasing plasma power and with increasing O2 pulse length before saturating at higher power and longer O2 pulse length. The growth rate saturated at the level of 1.78 Å·cycle,1. EDS analysis showed that the films were oxygen rich and had carbon as an impurity. This can be explained by the presence of bonds between hydrocarbons from the unreacted TMA precursor and excess oxygen in the film. ATR-FTIR spectroscopy measurements indicated a change in growth mechanism when the distance between the location of the radical generation and the substrate was varied. A similar effect was observed with the use of different plasma power levels. [source] Low-Temperature ABC-Type Atomic Layer Deposition: Synthesis of Highly Uniform Ultrafine Supported Metal Nanoparticles,ANGEWANDTE CHEMIE, Issue 14 2010Junling Lu Dr. Behütete Aufzucht: Eine neue Methode für die Synthese von einheitlichen, kleinen, trägerfixierten Metallnanopartikeln durch Atomlagenabscheidung (ALD) wird beschrieben. Der ALD-Prozess beruht auf der simultanen Abscheidung von geschützten Metallnanopartikeln und neuen Trägerschichten bei niedrigen Temperaturen. Anschließend werden die Metallnanopartikel aktiviert, indem die Schutzliganden durch Kalzinieren oder Reduktion bei erhöhten Temperaturen entfernt werden (siehe Bild). [source] Analysis of Al2O3 Atomic Layer Deposition on ZrO2 Nanoparticles in a Rotary Reactor,CHEMICAL VAPOR DEPOSITION, Issue 9 2007A. McCormick Abstract Al2O3 atomic layer deposition (ALD) is analyzed on ZrO2 nanoparticles in a rotary reactor. This rotary reactor allows for static exposures and efficiently utilizes the reactants for ALD on high surface area nanoparticles. The Al2O3 ALD is performed using exposures to Al(CH3)3 and H2O reactants. The pressure transients during these exposures are examined using a sequence of reactant micropulses. These micropulses are less than the required exposures for the ALD surface chemistry to reach completion. The pressure transients during identical sequential Al(CH3)3 and H2O micropulses change as the surface chemistry progresses to completion. These pressure transients allow the required saturation reactant exposure to be determined to maximize reactant usage. The ZrO2 nanoparticles are coated using various numbers of Al(CH3)3 and H2O reactant exposures. The Al2O3 ALD-coated ZrO2 nanoparticles are subsequently analyzed using a number of techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES), scanning AES (SAES), and X-ray photoelectron spectroscopy (XPS). The TEM images reveal very conformal Al2O3 ALD on the ZrO2 nanoparticles. The Al2O3 ALD thicknesses versus number of Al(CH3)3 and H2O reactant exposures yielded an Al2O3 ALD growth rate of 2.0,Å per reactant cycle. The AES and XPS results are consistent with an Al2O3 ALD film that completely and conformally covered the underlying ZrO2 nanoparticle. The SAES measurements show that the Al2O3 ALD films are continuous and homogeneous on the ZrO2 nanoparticles. These results demonstrate that a rotary reactor can successfully perform ALD with high reactant efficiency on high surface area nanoparticles. [source] Plasma-Enhanced Atomic Layer Deposition of Palladium on a Polymer Substrate,CHEMICAL VAPOR DEPOSITION, Issue 6-7 2007A. Ten, Eyck Abstract In this paper, a method for the plasma-enhanced (PE) atomic layer deposition (ALD) of palladium on air-exposed, annealed poly(p -xylylene) (Parylene-N, or PPX) is presented. Palladium is successfully deposited on PPX at 80,°C using a remote, inductively coupled, hydrogen/nitrogen plasma with palladium (II) hexafluoroacetylacetonate (PdII(hfac)2) as the precursor. By optimizing the mixture of hydrogen and nitrogen, the polymer surface is modified to introduce active sites allowing the chemisorption of the PdII(hfac)2. In addition, enough free hydrogen atoms are available at the surface for ligand removal and Pd reduction, while at the same time, enough hydrogen atoms are consumed in the plasma to ensure there is no visible degradation of the PPX. X-ray photoelectron spectroscopy (XPS) measurements of the substrate after hydrogen/nitrogen plasma treatment at 50,W clearly show the presence of nitrogen bound to the substrate surface. XPS measurements of the deposited Pd films indicate good quality for both substrates, suggesting that the substrate temperature was low enough to prevent dissociation of the hfac ligand and adequate scavenging of the hfac ligand by the available atomic hydrogen. The remote hydrogen/nitrogen plasma enables Pd film deposition on polymer surfaces, which do not typically react with the Pd precursor, and are not catalysts for the dissociation of molecular hydrogen. [source] Atomic Layer Deposition of BaTiO3 Thin Films,Effect of Barium Hydroxide FormationCHEMICAL VAPOR DEPOSITION, Issue 5 2007M. Vehkamäki Abstract Barium titanate thin films are grown by atomic layer deposition (ALD) at 340,°C from barium cyclopentienyl and titanium methoxide precursors. H2O is used as the oxygen source. Binary reactions of Ba(tBu3C5H2)2 and H2O are first studied separately in BaO deposition and are found to result in a hydration/dehydration cycle, which is strongly influenced by the process temperature. Self-limiting growth of amorphous barium titanate films becomes possible when Ti(OMe)4 , H2O growth cycles are mixed as well as possible with Ba(tBu3C5H2)2 , H2O cycles. The as-deposited amorphous films are crystallized by post-deposition annealing at 600,°C. Permittivities of 15 and 70 are measured for as-deposited and post-deposition annealed films, respectively. A charge density of 1.9 ,C cm,2 (equivalent oxide thickness of 1.8,nm) and leakage current density ,,1,×,10,7,A,cm,2 were achieved at 1,V bias with a 32,nm thick Ba,Ti,O film in a Pt electrode stack annealed at 600,°C. [source] Self-Assembled Octadecyltrimethoxysilane Monolayers Enabling Selective-Area Atomic Layer Deposition of IridiumCHEMICAL VAPOR DEPOSITION, Issue 7 2006E. Färm A preparation method for octadecyltrimethoxysilane (ODS) self-assembled monolayers (SAMs) that enables the selective-area ALD of iridium is studied using an ALD process for iridium at 225,°C. ODS SAMs were prepared from the gas phase by two preparation methods: either with exposure to ODS only, or with alternate exposures to ODS and water. SAMs were patterned with a lift-off process using aluminium as a mask layer. [source] Atomic Layer Deposition, Characterization, and Dielectric Properties of HfO2/SiO2 Nanolaminates and Comparisons with Their Homogeneous Mixtures,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2006L. Zhong Abstract Nanolaminates of HfO2 and SiO2 were prepared using atomic layer deposition (ALD) methods. Successive exposure of substrates maintained at 120 or 160,°C to nitrogen flows containing Hf(NO3)4 and (tBuO)3SiOH led to typical bilayer spacings of 2.1,nm, with the majority of each bilayer being SiO2. The density of the SiO2 layers (measured using X-ray reflectometry (XRR)) was slightly higher than expected for amorphous silica, suggesting that as much as 10,% HfO2 was incorporated into the silica layers. Based on cross-sectional transmission electron microscopy (TEM) and XRR, oxidation of the silicon substrate was observed during its first exposure to Hf(NO3)4, leading to a SiO2 interfacial layer and the first HfO2 layer. Combining the ALD of Hf(NO3)4/(tBuO)3SiOH with ALD cycles involving Hf(NO3)4 and H2O allowed the systematic variation of the HfO2 thickness within the nanolaminate structure. This provided an approach towards controlling the dielectric constant of the films. The dielectric constant was modeled by treating the nanolaminate as a stack of capacitors wired in series. The nanolaminate structure inhibited the crystallization of the HfO2 in post-deposition annealing treatments. As the HfO2 thickness decreased, the preference for the tetragonal HfO2 phase increased. [source] Random Deposition as a Growth Mode in Atomic Layer Deposition (Chem. Vap.CHEMICAL VAPOR DEPOSITION, Issue 5 2005Deposition 200 Abstract To view the original paper use http://dx.doi.org/10.1002/cvde.200306283. [source] Formation of Metal Oxide Particles in Atomic Layer Deposition During the Chemisorption of Metal Chlorides: A Review,CHEMICAL VAPOR DEPOSITION, Issue 2 2005L. Puurunen Abstract As has been known for a decade, metal oxide particles can form in a single reaction of gaseous metal chlorides with solid oxides. This is an undesirable effect in the fabrication of thin films by atomic layer deposition (ALD). This work reviews the experimental results related to the metal oxide particle formation and the mechanisms suggested to account for it. The suggested mechanisms cannot explain the observations, but systematic analysis of the possible reaction paths delivers one reaction mechanism candidate, based on a reaction between surface chlorine groups and the hydroxyl groups of gaseous metal hydroxychloride intermediates. The consequences of the proposed mechanism are discussed. [source] Growth Per Cycle in Atomic Layer Deposition: A Theoretical Model (Chem. Vap.CHEMICAL VAPOR DEPOSITION, Issue 3 2004Deposition 200 To view the original paper use http://dx.doi.org/10.1002/cvde.200306265. [source] Random Deposition as a Growth Mode in Atomic Layer Deposition,CHEMICAL VAPOR DEPOSITION, Issue 3 2004R.L. Puurunen Abstract Despite the increasing number of successful applications of material growth by atomic layer deposition (ALD), the description of many physicochemical processes that occur during ALD growth is still incomplete. The way the material is arranged on the surface during ALD growth, called the ALD growth mode, defines important material properties, such as when the substrate gets fully covered by the ALD-grown material, and the surface roughness. This work initiates the theoretical description of ALD growth modes by describing the random deposition growth mode, both qualitatively and quantitatively, by using the growth per cycle as a statistical quantity. [source] Growth Per Cycle in Atomic Layer Deposition: Real Application Examplesof a Theoretical Model,CHEMICAL VAPOR DEPOSITION, Issue 6 2003R.L. Puurunen Abstract In a previous paper, a theoretical model was derived to describe the growth per cycle in atomic layer deposition (ALD) as a function of the chemistry of the growth when compounds are used as reactants. This paper presents examples of how the model can be applied to investigate the mechanisms of real ALD processes. Three processes that represent different classes of compound reactants were selected for study: the trimethylaluminum/water process to grow aluminum oxide, the yttrium 2,2,6,6-tetramethyl-3,5-heptanedionate (thd)/ozone process to grow yttrium oxide, and the titanium tetrachloride/water process to grow titanium dioxide. The results obtained by applying the model were, in general, consistent with the results obtained through separate investigations of the reaction mechanisms. The model was shown to be a useful tool in investigations of the reaction chemistry of real ALD processes. [source] Atomic Layer Deposition of Hafnium Dioxide Films from Hafnium Hydroxylamide and Water.CHEMINFORM, Issue 22 2004Kaupo Kukli Abstract For Abstract see ChemInform Abstract in Full Text. [source] Silver Coated Platinum Core,Shell Nanostructures on Etched Si Nanowires: Atomic Layer Deposition (ALD) Processing and Application in SERSCHEMPHYSCHEM, Issue 9 2010Vladimir A. Sivakov Dr. Abstract A new method to prepare plasmonically active noble metal nanostructures on large surface area silicon nanowires (SiNWs) mediated by atomic layer deposition (ALD) technology has successfully been demonstrated for applications of surface-enhanced Raman spectroscopy (SERS)-based sensing. As host material for the plasmonically active nanostructures we use dense single-crystalline SiNWs with diameters of less than 100 nm as obtained by a wet chemical etching method based on silver nitrate and hydrofluoric acid solutions. The SERS active metal nanoparticles/islands are made from silver (Ag) shells as deposited by autometallography on the core nanoislands made from platinum (Pt) that can easily be deposited by ALD in the form of nanoislands covering the SiNW surfaces in a controlled way. The density of the plasmonically inactive Pt islands as well as the thickness of noble metal Ag shell are two key factors determining the magnitude of the SERS signal enhancement and sensitivity of detection. The optimized Ag coated Pt islands on SiNWs exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability and reproducibility. The plasmonic activity of the core-shell Pt//Ag system that will be experimentally realized in this paper as an example was demonstrated in numerical finite element simulations as well as experimentally in Raman measurements of SERS activity of a highly diluted model dye molecule. The morphology and structure of the core-shell Pt//Ag nanoparticles on SiNW surfaces were investigated by scanning- and transmission electron microscopy. Optimized core,shell nanoparticle geometries for maximum Raman signal enhancement is discussed essentially based on the finite element modeling. [source] Atomic Layer Deposition of UV-Absorbing ZnO Films on SiO2 and TiO2 Nanoparticles Using a Fluidized Bed Reactor,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2008David M. King Atomic layer deposition (ALD) was used to apply conformal, nanothick ZnO coatings on particle substrates using a fluidized bed reactor. Diethylzinc (DEZ) and water were used as precursors at 177,°C. Observed growth rates were ca. 2.0 Å/cycle on primary particles as verified by HRTEM. ICP-AES and XPS were used to quantify Zn:substrate ratios. Layers of 6, 18, and 30 nm were deposited on 550 nm SiO2 spheres for UV blocking cosmetics particles. TiO2 nanoparticles were coated in the second part of this work by ZnO shells of 2, 5, and 10 nm thickness as novel inorganic sunscreen particles. The specific surface area of powders changed appropriately after nanothick film deposition using optimized conditions, signifying that high SA particles can be functionalized without agglomeration. The ZnO layers were polycrystalline as deposited and narrowing of the FWHM occurred upon annealing. Annealing the ZnO-TiO2 nanocomposite powder to 600,°C caused the formation of zinc titanate (Zn2TiO4) in both oxygen-rich and oxygen-deficient environments. The non-ideal surface behavior of the DEZ precursor became problematic for the much longer times required for high surface area nanoparticle processing and results in Zn-rich films at this growth temperature. In situ mass spectrometry provides process control capability to functionalize bulk quantities of nano- and ultrafine particles without significant precursor waste or process overruns. ZnO overlayers can be efficiently deposited on the surfaces of primary particles using ALD processing in a scalable fluidized bed reactor. [source] Multilayered Core/Shell Nanowires Displaying Two Distinct Magnetic Switching Events,ADVANCED MATERIALS, Issue 22 2010Yuen Tung Chong Atomic layer deposition (ALD) and electrodeposition are combined with a porous template to create ordered arrays of nanowires in which a nickel core and an iron oxide shell are separated by a silica spacer layer. The switching of each magnetic component is distinct and occurs at a field that depends on the tunable thicknesses of the various layers. [source] | ||||||||||||||||