We use first-principles density functional theory (DFT) calculations to investigate the ground-state structures of PbTiO(3) solid solutions containing Ni, Pd, and Pt. Anomalous effective charges are reported, including the first report of negative Born effective charges for nominal +2 cations. We predict that these proposed materials will display a decreased band gap when compared to PbTiO(3) w...

A magnetic-field-driven transition from metallicto semiconducting-type behavior in the basal-plane resistance takes place in highly oriented pyrolytic graphite at a field Hc ∼ 1 kOe applied along the hexagonal c-axis. The analysis of the data reveals a striking similarity between this transition and that measured in thinfilm superconductors and Si MOSFET’s. However, in contrast to those materia...

The electronic structure of the VAs compound in the zinc-blende structure is investigated using a combined density-functional and dynamical mean-field theory approach. Contrary to predictions of a ferromagnetic semiconducting ground state obtained by density-functional calculations, dynamical correlations induce a closing of the gap and produce a half-metallic ferromagnetic state. These results...

This article gives an overview of the use of X-ray absorption spectroscopy to characterize the magnetic properties for technologically important, low dimensional magnetic materials. An overview is given both for the experimental hardware, the measurements and the analysis of the spectra. The information obtained is discussed for metallic and semiconducting systems, using both the X-ray magnetic...

Z. Naturforsch. 54 b, 573-576 (1999); eingegangen am 28. Dezember 1998 Fused Salts, Monosilane, Methylsilanes, Hydrosilylation, Chloroaluminate Silanes of technical interest as starting compounds for semiconducting materials or hydrosi­ lylation reactions, (CH3)xSiH4_x (x = 0, 1,2, 3), are obtained by direct hydrogenation of the corresponding chlorosilanes in the presence of various interstitia...

NREL has recently begun investing polymer-based photovoltaic cells. We present initial results on a novel energy conversion device that uses both semiconducting polymers and organic small molecules as photoactive layers, using the advantageous properties of both classes of materials. By incorporating polymers into the device, we see results that are surprisingly good for a planar organic device...

Monolayer membranes of conjugated carbon represent a class of nanomaterial with demonstrated uses in various areas of electronics, ranging from transparent, flexible, and stretchable thin film conductors, to semiconducting materials in moderate and high-performance field-effect transistors. Although graphene represents the most prominent example, many other more structurally and chemically dive...

A strong optical Stark effect has been observed in (6,5) semiconducting single-walled carbon nanotubes by femtosecond pump-probe spectroscopy. The response is characterized by an instantaneous blueshift of the excitonic resonance upon application of pump radiation at photon energy well below the band gap. The large Stark effect is attributed to the enhanced Coulomb interactions present in these...

A great deal of interest in two-dimensional materials analogues of graphene has appeared among the scientific community since the demonstration of isolated 2D atomic plane crystals from bulk crystals [1]. Dimensionality is key for the definition of material properties and the same chemical compound can exhibit dramatically different properties depending on whether it is arranged in dots (0D), w...

The use of metal organic frameworks (MOFs) as heterogeneous photocatalysts is critically reviewed. First we revisit the general assumption of MOFs behaving truly as semiconductors, demonstrating that such semiconducting behaviour only occurs in a very limited subset of materials. Further, the main approaches for efficient light harvesting and active site engineering in MOF-based photocatalysts ...