Search results for "layer"
showing 10 items of 2667 documents
Epitaxy of thin films of the Heusler compound
2007
Abstract Epitaxial thin films of the highly spin polarized Heusler compound Co 2 Cr 0.6 Fe 0.4 Al are deposited by DC magnetron sputtering. It is shown by XRD and TEM investigations how the use of an Fe buffer layer on MgO(1 0 0) substrates supports the growth of highly ordered Co 2 Cr 0.6 Fe 0.4 Al at low deposition temperatures. The as-grown samples show a relatively large ordered magnetic moment of μ ≃ 3.0 μ B / f . u . providing evidence for a low level of disorder.
Monte Carlo Study of Dense Monolayer and Bilayer Films on the (100) Plane of Face-Centered Cubic Crystals
1999
A Monte Carlo simulation method in the canonical and in the grand canonical ensembles is used to study the behavior and properties of dense monolayer and bilayer films formed on the (100) plane of model face-centered cubic crystals. Systems with different effects due to the periodicity of the gas−solid potential are considered, and the mechanism of melting in the first and the second adsorbed layer is discussed. It is demonstrated that the film structure is very sensitive to the gas−solid potential corrugation, as well as to the temperature and the surface coverage. In particular, it is shown that monolayer films formed on weakly corrugated surfaces exhibit the incommensurate (dense) phase …
Lattice gas models for multilayer adsorption: variation of phase diagrams with the strength of the substrate potential
1990
Abstract The simple cubic lattice gas model with nearest-neighbor attractive interaction is considered for the case where the potential V ( z ), that an adatom at a distance z from the surface experiences due to the substrate, is V ( z ) = − A / z 3 . Exact ground state phase diagrams are obtained for different A , while the behavior at nonzero temperatures is studied both by Monte Carlo simulations and the molecular field approximation. We show that the detailed sequence of the layering transitions in the first few layers depends very strongly on the strength of the substrate potential: for strong potentials individual first-order layering transitions in layers 1, 2, 3, …, while for interm…
Efficient, Cyanine Dye Based Bilayer Solar Cells
2012
Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors and evaporated C60 layer as an acceptor are prepared. Cyanine dyes with absorption maxima of 578, 615 and 697 nm having either perchlorate or hexafluorophosphate counter-ions are evaluated. The perchlorate dye leads to cells with S-shape current-voltage curves; only the dyes with the hexafluorophosphate counter-ions lead to efficient solar cells. When the wide bandgap dyes are employed, S-shape current-voltage curves are obtained when the conductive polymer PEDOT:PSS is used as hole transport layer. Substitution of PEDOT:PSS with MoO3 leads to cells with more rectangular current–voltage curves and high …
Biochemical Applications of Solid Supported Membranes on Gold Surfaces: Quartz Crystal Microbalance and Impedance Analysis
2003
Since their inception in 1985 by Tamm and McConnell [1], solid supported lipid bilayers have been widely used as model systems for cellular membranes [2]. They have been applied in fundamental and applied studies of lipid assemblies on surfaces, to study the structure of membranes and membrane dynamics, lipidreceptor-interactions and electrochemical properties of membranes [3-5]. Several attempts have been made to apply solid supported membranes (SSM) in biosensor devices [6]. Planar lipid membranes can be formed on various surfaces, i.e. glass, silicon, mica or metal surfaces such as platinum or gold. Surface attachment of the lipids is typically achieved following two different strategies…
Reduced efficiency roll-off in light-emitting diodes enabled by quantum dot–conducting polymer nanohybrids
2014
We demonstrate QLEDs implementing wider active layers (50 nm) based on QD–conducting polymer nanohybrids, which exhibit a stable operational device performance across a wide range of current densities and brightness. A comparative study reveals that the significant suppression of efficiency roll-off in the high current density regime is primarily attributed to a sufficient charge carrier distribution over the wider active layer and improved charge carrier balance within QDs enabled by the hybridization of QDs with conducting polymers. Utilization of this finding in future studies should greatly facilitate the development of high performance, stable QLEDs at high current density or luminance…
Tailored conjugated polymer Langmuir-Schafer thin films in sensing transistors
2004
Organic Thin Film Transistors (OTFTs) have been fabricated, in a standard bottom gate configuration, with Langmuir-Schäfer (LS) or cast thin films of regioregular poly[1,4-(2,5-dioctyloxyphenylene)-2,5-thiophene], synthesized via an organometallic protocol, as active layers. The transistors electrical characterization has evidenced that LS based devices exhibit better performance level than cast film ones. Appealing perspectives for newly substituted conjugated polymers in OTFT sensing devices are discussed.
Tuning Of Organic Heterojunction Conductivity By The Substituents' Electronic Effects In Phthalocyanines For Ambipolar Gas Sensors
2021
Abstract Exploiting organic heterojunction effects in electrical devices are an important strategy to improve the electrical conductivity, which can be utilized into improving the conductometric gas sensors performances. In this endeavor, the present article reports fabrication of organic heterostructures in a bilayer device configuration incorporating octa-substituted nickel phthalocyanines (NiPc) and radical lutetium bis-phthalocyanine (LuPc2) and investigates their sensing properties towards NH3 vapor. NiPc having hexyl sulfanyl, hexyl sulfonyl and p-carboxyphenoxy moieties are synthesized, which electronic effects are electron donating, accepting and moderate accepting, respectively, al…
Staphylococcal α-toxin: the role of the N-terminus in formation of the heptameric pore — a fluorescence study1This work contains parts of the M.D. th…
1997
Staphylococcus aureus alpha-toxin forms heptameric pores on eukaryotic cell membranes. Assembly of the heptamer precedes formation of the transmembrane pore. The latter event depends on a conformational change that drives a centrally located stretch of 15 amino acid residues into the lipid bilayer. A second region of the molecule that has been implicated in the pre-pore to pore transition is the far N-terminus. Here, we used fluorescently labeled single cysteine replacement mutants to analyze the functional role of the far N-terminus of alpha-toxin. Pyrene attached to mutants S3C, I5C and 17C forms excimers within the toxin pore complex. This indicates that the distance of adjacent N-termin…
Interaction ofEscherichia colihemolysin with biological membranes
2001
Escherichia coli hemolysin (HlyA) is a membrane-permeabilizing protein belonging to the family of RTX-toxins. Lytic activity depends on binding of Ca2(+) to the C-terminus of the molecule. The N-terminus of HlyA harbors hydrophobic sequences that are believed to constitute the membrane-inserting domain. In this study, 13 HlyA cysteine-replacement mutants were constructed and labeled with the polarity-sensitive fluorescent probe 6-bromoacetyl-2-dimethylaminonaphthalene (badan). The fluorescence emission of the label was examined in soluble and membrane-bound toxin. Binding effected a major blue shift in the emission of six residues within the N-terminal hydrophobic domain, indicating inserti…