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We demonstrate that a statistically-significant chiral bias in NaClO3 chiral crystallization can be provoked by inducing nucleation via the optical trapping of Ag nano-aggregates using a continuous wave visible circularly polarized laser (λ = 532 nm). The laser was focused at the interface between air and an unsaturated NaClO3 aqueous solution containing Ag nanoparticles. The “dominant” enantiomorph was switchable by changing the handedness of the incident circularly polarized laser, indicating that the chiral bias is enantioselective. Moreover, it has been found that the resulting crystal enantiomeric excess (CEE) reached approximately 25%. The CEE is much higher than the typical enantiomeric excess (EE) in the asymmetric photosynthesis of organic compounds ranging from 0.5 to 2%. The efficient induction of the nucleation and the large chiral bias imply the contribution of localized surface plasmon resonance of the Ag nanoaggregates to chiral nucleation. Our method has potential to offer the benefit for studies on the spatiotemporal nucleation control, optical resolution of chiral compounds and biohomochirality. [ABSTRACT FROM AUTHOR]

Superconducting NdFeAs(O,F) thin films were grown on GaAs substrates by molecular beam epitaxy. Films grown with a sufficiently long growth time exhibited a clear superconducting transition with an onset temperature up to 48 K and zero resistance temperature up to 42 K without the need of an ex situ annealing process. Electron probe microanalysis and Hall coefficient measurements indicated that the superconducting films are doped with fluorine, and depth-profile analysis by Auger electron spectroscopy revealed the formation of a NdOF layer near the surface, which is probably connected with the fluorine doping. [ABSTRACT FROM AUTHOR]

In order to improve size uniformity of InAs quantum dots (QDs) on (001) InP substrates using droplet heteroepitaxy by metal-organic vapor phase epitaxy, the authors carried out the growth of InAs QDs on size-controlled linear mesa-structure templates fabricated by using selective-area growth technique and surrounded by facet planes. InAs QDs preferentially formed on the (001) top surface facet. The maximum size of QD was limited by the width of the top surface. On the other hand, the minimum size was defined by the practically critical size. These facts imply that the narrow width of the top surface of templates controls the dispersion of size distribution. The authors obtained the narrow photoluminescence peak from the size-controlled InAs QDs with full width at half maximum of 85 meV at around 1.5 μm wavelength. [ABSTRACT FROM AUTHOR]

BaFe2(As, P)2 thin films were grown by molecular beam epitaxy. Single phase and c-axis oriented thin films were obtained on both LaAlO3 (LAO) and MgO substrates. The critical temperature (Tc) of the thin films grown on LAO substrates showed a P content dependence very similar to single crystals, while those grown on MgO showed a distinctly different dependence. Lattice parameter measurements showed that the thin films grown on MgO were under tensile strain, while no structural deformation was observed for the thin films grown on LAO substrates. The strain effect accounts well for the difference in the P content dependence of Tc. We also obtained the Poisson’s ratio from the observed strain, which gave a reasonable value and a systematic change with the P content. [ABSTRACT FROM AUTHOR]

A spin-polarized electron beam has been used as the probe beam in a transmission electron microscope by using a photocathode electron gun with a photocathode made of a GaAs-GaAsP strained superlattice semiconductor with a negative electron affinity (NEA) surface. This system had a spatial resolution of the order of 1 nm for at 30 keV and it can generate an electron beam with an energy width of 0.24 eV without employing monochromators. This narrow width suggests that a NEA photocathode can realize a high energy resolution in electron energy-loss spectroscopy and a longitudinal coherence of 3 × 10-7 m. [ABSTRACT FROM AUTHOR]

SiGe bulk crystal fabricated by a multicomponent zone-melting method was used as a substrate for epitaxial growth of GaAs. Compared with conventional GaAs/Ge heterostructure, the lattice mismatch of GaAs/Si[sub 0.022]Ge[sub 0.978] was confirmed to be reduced by a decrease of the peak separation of (400) x-ray diffraction from the epitaxial GaAs layer and the substrate. Furthermore, the linewidth of the rocking curve of GaAs on SiGe was found to be narrower than that of GaAs on Ge. These results show that SiGe is promising material as an alternative substrate to Ge for realization of exactly lattice-matched GaAs/SiGe solar cells. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]