Search results for "layer"
showing 10 items of 2667 documents
Multiphysical modeling of dissimilar welding via interlayer
2011
Abstract A multiphysical finite element modeling of dissimilar welding via interlayer material was proposed. A 2D model including heat transfer, fluid flow and level set problems allowed to simulate the morphology and the composition of melted zone in horizontal plane. The calculated thickness of melted interlayer was used as a main criterion for the choice of optimal welding conditions, when the chemical interaction between the joined materials must be avoided. A 1D diffusion model at the limit of melted zone allowed estimating the length and the composition of diffusion layer between one of the materials and the interlayer basing on previously calculated local temperature gradient. The si…
Electrochemical deposition of polypyrrole nanolayers on discontinuous ultrathin gold films.
2008
Ultrathin layers of polypyrrole (PPy) were electrochemically grown between microelectrodes on a $Si/SiO_2$ substrate. Conducting nanolayers of PPy are directly grown onto ultrathin discontinuous gold (Au) film between the microelectrodes, with thicknesses in the range 10–100 nm. The system therefore forms a novel (PPy/Au) nanocomposite conductor. Atomic force microscopy (AFM) imaging and conductivity measurements indicate that at all thicknesses a relatively uniform film is formed but with significant roughness that reflects the roughness of the metallic island layer. In PPy/Au films with thickness $\sim 10 nm$, the small barriers around the gold islands dominate the conduction, and as the …
NMR-investigation of the mechanism of silver mercaptide thermolysis in amorphous polystyrene
2007
Polymer-embedded silver clusters have been prepared by thermal decomposition of silver dodecylmercaptide previously dissolved in amorphous polystyrene. The morphology and structure of silver clusters have been determined by transmission electron microscopy (TEM) and large angle X-ray diffractometry (XRD), respectively. The mechanism involved in the thermolysis reaction was elucidated by different NMR techniques. The thermolysis produced thiol-derivatized silver clusters (i.e., silver clusters coated with a self-organized thiol monolayer, Agx(SC12H25)y) and had the effect of increasing the branching degree of polystyrene due to enhanced cross-linking.
Cover Picture: Nanoscale Deposition of Single-Molecule Magnets onto SiO2 Patterns (Adv. Mater. 2/2007)
2007
The cover shows a schematic of scanning probe nanolithography based on the spatial confinement of an oxidation reaction within a water meniscus, and its application for fabricating ordered arrays of cationic Mn12 single-molecule magnets. Romero, Coronado, Garcia, and co-workers report on p. 291 that electrostatic interactions between the molecules and trapped charges within the nanodots drive the positioning of the molecules at the nanoscale.
Advances in SPMs for Investigation and Modification of Solid-Supported Monolayers
2007
Improvement in nanotechnology research has been strongly driven by the advancement that nanoscale characterization and manipulation tools made from the beginning. Solidsupported monolayers (SSMs) represent one of the most important systems in nanotechnology. High-quality SSMs may be fabricated at low cost by solution processes employing techniques like self-assembly and Langmuir–Blodgett methods. In the last decade, advances in scanning probe methods provided more and more efficient tools able both to probe with largely improved resolution the morphological features of SSMs and to modify selectively their functional groups. The modified self-assembled monolayers can be used as nanotemplates…
Phase Composition and Nanoporous Structure of Core and Surface in the Modified Granules of NH4NO3
2018
The article deals with the study of phase composition and crystal nanoporous structure of core and surface layer of porous ammonium nitrate (PAN). The research results, presented in the article, show that the proposed way to generate PAN allows to provide the granule porous structure without changing of its phase composition. The crystal structure of granules after the humidification and heat treatment has some changes due to the increase of the number of pores. The change of crystal structure, in turn, allows to open access to nanopores that are located in the volume of granules. This allows to increase the holding capacity indicator of granules. An important result of conducted researches…
Suppression of Forward Electron Injection from Ru(dcbpy)2(NCS)2 to Nanocrystalline TiO2 Film As a Result of an Interfacial Al2O3 Barrier Layer Prepar…
2009
Subnanometer-thick Al2O3 barrier layers on nanocrystalline TiO2 film were prepared with atomic layer deposition (ALD). The method allowed variation of barrier thicknesses at atomic resolution also deep in nanoporous structures, which makes it a superior method as compared to, e.g., sol−gel techniques. In this letter we present results on the effect of Al2O3 barriers of various thicknesses on forward electron injection in dye-sensitized solar cells. A decrease in the amplitude of the oxidized Ru(dcbpy)2(NCS)2 dye absorption signal due to singlet injection was observed already after one deposition cycle that produces a discontinuous layer with nominal thickness of 1 A. More than two layer coa…
Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films
2016
Plasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N2:H2 plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the…
Morphological evolution of InAs/InP quantum wires through aberration-corrected scanning transmission electron microscopy
2010
Evolution of the size, shape and composition of self-assembled InAs/InP quantum wires through the Stranski–Krastanov transition has been determined by aberration-corrected Z-contrast imaging. High resolution compositional maps of the wires in the initial, intermediate and final formation stages are presented. (001) is the main facet at their very initial stage of formation, which is gradually reduced in favour of {114} or {118}, ending with the formation of mature quantum wires with {114} facets. Significant changes in wire dimensions are measured when varying slightly the amount of InAs deposited. These results are used as input parameters to build three-dimensional models that allow calcu…
Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods
2013
Metal oxides are versatile substrates for the design of a wide range of SAM-based organic-inorganic materials among which ZnO nanostructures modified with phosphonic SAM are promising semiconducting systems for applications in technological fields such as biosensing, photonics, and field-effect transistors (FET). Despite previous studies reported on various successful grafting approaches, issues regarding preferred anchoring modes of phosphonic acids and the role of a second reactive group (i.e., a carboxylic group) are still a matter of controversial interpretations. This paper reports on an experimental and theoretical study on the functionalization of ZnO nanorods with monofunctional alk…