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Selected Peer-Reviewed Articles from the 5th International Conference on Surfaces, Coatings and Nanostructured Materials (NANOSMAT 2010)

REA Auditado

Tema: general: 

• Ciencias

Unification of trap-limited electron transport in semiconducting polymers

REA Auditado

Electron transport in semiconducting polymers is usually inferior to hole transport, which is ascribed to charge trapping on isolated defect sites situated within the energy bandgap. However, a general understanding of the origin of these omnipresent charge traps, as well as their energetic position, distribution and concentration, is lacking. Here we investigate electron transport in a wide range of semiconducting polymers by current–voltage measurements of single-carrier devices.

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Ferroelectric Phase Diagram of PVDF:PMMA

REA Auditado

We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of α- and β-phase PVDF was identified. Ferroelectric β-PVDF:PMMA blend films were made by melting, ice quenching, and subsequent annealing above the glass transition temperature of PMMA, close to the melting temperature of PVDF.

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Localizing trapped charge carriers in NO2 sensors based on organic field-effect transistors

REA Auditado

Field-effect transistors have emerged as NO2 sensors. The detection relies on trapping of accumulated electrons, leading to a shift of the threshold voltage. To determine the location of the trapped electrons we have delaminated different semiconductors from the transistors with adhesive tape and measured the surface potential of the revealed gate dielectric with scanning Kelvin probe microscopy. We unambiguously show that the trapped electrons are not located in the semiconductor but at the gate dielectric. The microscopic origin is discussed.

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Spin–lattice coupling in iron jarosite

REA Auditado

We have studied the magnetoelectric coupling of the frustrated triangular antiferromagnet iron jarosite using Raman spectroscopy, dielectric measurements and specific heat. Temperature dependent capacitance measurements show an anomaly in the dielectric constant at TN. Specific heat data indicate the presence of a low frequency Einstein mode at low temperature. Raman spectroscopy confirms the presence of a new mode below TN that can be attributed to folding of the Brillouin zone. This mode shifts and sharpens below TN.

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Probing orbital fluctuations in RVO3 (R = Y, Gd, or Ce) by ellipsometry

REA Auditado

We study optical excitations across the Mott gap in the multiorbital Mott-Hubbard insulators RVO3. The multipeak structure observed in the optical conductivity can be described consistently in terms of the different 3d3 multiplets or upper Hubbard bands. The spectral weight is very sensitive to nearest-neighbor spin-spin and orbital-orbital correlations and thus shows a pronounced dependence on both temperature and polarization.

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Fluid–structure interaction of three-dimensional magnetic artificial cilia

REA Auditado

A numerical model is developed to analyse the interaction of artificial cilia with the surrounding fluid in a three-dimensional setting in the limit of vanishing fluid inertia forces. The cilia are modelled using finite shell elements and the fluid is modelled using a boundary element approach. The coupling between both models is performed by imposing no-slip boundary conditions on the surface of the cilia. The performance of the model is verified using various reference problems available in the literature.

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Anisotropy of spin polarization and spin accumulation in Si/Al2O3/ferromagnet tunnel devices

REA Auditado

The contribution of the spin accumulation to tunneling anisotropy in Si/Al2O3/ferromagnet devices was investigated. Rotation of the magnetization of the ferromagnet from in-plane to perpendicular to the tunnel interface reveals a tunneling anisotropy that depends on the type of the ferromagnet (Fe or Ni) and on the doping of the Si (n or p type). Analysis shows that different contributions to the anisotropy coexist. Besides the regular tunneling anisotropic magnetoresistance, we identify a contribution due to anisotropy of the tunnel spin polarization of the oxide/ferromagnet interface.

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Selective transformations of complex molecules are enabled by aptameric protective groups

REA Auditado

Emerging trends in drug discovery are prompting a renewed interest in natural products as a source of chemical diversity and lead structures. However, owing to the structural complexity of many natural compounds, the synthesis of derivatives is not easily realized. Here, we demonstrate a conceptually new approach using oligonucleotides as aptameric protective groups.

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DNA Block Copolymers: Functional Materials for Nanoscience and Biomedicine

REA Auditado

We live in a world full of synthetic materials, and the development of new technologies builds on the design and synthesis of new chemical structures, such as polymers. Synthetic macromolecules have changed the world and currently play a major role in all aspects of daily life. Due to their tailorable properties, these materials have fueled the invention of new techniques and goods, from the yogurt cup to the car seat belts. To fulfill the requirements of modern life, polymers and their composites have become increasingly complex.

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