TECHNIQUES FOR PRODUCING DEFECT-FREE SOI BY DUAL ELECTRON BEAM HEATING OF DEPOSITED POLYSILICON.

Advances in the dual electron-beam recrystallization technique arising from the fast scanning of a line beam parallel to the edges of narrow seeding windows are described. The resultant recrystallized layers are essentially defect-free, have good surface flatness, and cover large areas.

Magnetotunnelling spectroscopy: an experimental tool for studying chaos in quantum transport

Resonant tunnelling spectroscopy is used to investigate the energy level spectrum of a wide potential well in the presence of a large magnetic field oriented at angles θ between 0° and 90° to the normal to the plane of the well. In the tilted field geometry, the current-voltage characteristics exhibit a large number of quasiperiodic resonant peaks even though the classical motion of electrons in the potential well is chaotic. The voltage range and spacing of the resonances both change dramatically with θ. We give a quantitative explanation for this behaviour by considering the classical period of unstable periodic orbits within the chaotic sea of the potential well.

1 × 4 space switching and simultaneous all-optical wavelength conversion at 2.488Gbit/s using a single monolithically integrated multiwavelength laser

A novel InGaAs/InGaAsP/InP integrated multiwavelength grating cavity laser is presented, which has been used to demonstrate space switching and simultaneous all-optical wavelength conversion at bit rates of 2.488 Gbit/s. This has been achieved using a single monolithically integrated device without the need for post-filtering to separate the converted signal from the input.

Reduction of porosity in RE1Ba2Cu3Oy pseudo crystals

The distribution of porosity in Y1Ba2Cu3Oy (Y-123) pseudo-crystals prepared by hot seeded melt growth of precursor pellet samples pre-sintered at elevated temperatures in air or vacuum has been investigated. The results demonstrate that the porosity within the Y-123 pseudo-crystal matrix could be reduced dramatically by pre-sintering in vacuum, compared with that for precursor pellets processed in air.

Fabrication of large grain Nd-Ba-Cu-O by seeded melt growth

Large, single grain Nd-Ba-Cu-O (NdBCO) composite samples of NdBa2Cu3O7-δ (Nd-123) containing 15 and 20 mol. % non-superconducting Nd4Ba2Cu2O10 (Nd-422) phase inclusions have been fabricated successfully by a variety of techniques based on top-seeded melt growth under reduced oxygen partial pressure. Specifically, individual grains up to 2cm in diameter have been grown using (100) oriented MgO seeding, self (NdBCO) seeding at elevated temperature and self-seeding of Ag and Au doped precursor pellets. The latter exhibit a reduced peritectic decomposition temperature compared with the undoped compound. These techniques, which vary in degree of difficulty and hence reliability, yield grains with a range of microstructural homogeneity. This paper describes the general aspects of large NdBCO grain fabrication and presents the results of the different fabrication techniques.

Hafnia nanoparticles - a model system for graphene growth on a dielectric

We study graphene growth on hafnia (HfO2) nanoparticles by chemical vapour deposition using optical microscopy, high resolution transmission electron microscopy and Raman spectroscopy. We find that monoclinic HfO2 nanoparticles neither reduce to a metal nor form a carbide while nucleating nanometer domain-sized few layer graphene. Hence we regard this as an interesting non-metallic catalyst model system with the potential to explore graphene growth directly on a (high-k) dielectric. HfO2 nanoparticles coated with few layer graphene by atmospheric pressure CVD with methane and hydrogen at 950 °C. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Graphene growth on hafnia (HfO2) nanoparticles by chemical vapour deposition (CVD) is studied. It is found that monoclinic HfO2 nanoparticles neither reduce to a metal nor form a carbide while nucleating nanometer domain-sized few layer graphene. Hence the authors of this Letter regard this as an interesting non-metallic catalyst model system with the potential to explore graphene growth directly on a (high-k) dielectric. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.