[en] The surface layer of an epitaxial Fe/Cr multilayer system has been structured lithographically into stripes with 1 μm period. Polarized neutron reflectometry and diffuse scattering under grazing incidence measurements show strongly enhanced domain formation compared to the unstructured sample. The domains are correlated throughout the layers. The lateral domain size is partly the period of the stripe pattern of the surface layer, and partly the double

[en] A flexible electrode hose of 1 m length and with a diameter of 18 mm, consisting of two helically wound wires has been built. Its ability to guide a low-energy Ar ion beam of 1 keV and 100 μA has been tested with electrode potentials up to 500 V. The Smooth Approximation of the equation of motion leads to a focussing effective boundary potential and to a critical glancing angle for ion beam reflection. Similarities with light and neutron guides are discussed. Measurements of the guided ion beam show that the beam is attenuated by atomic charge transfer along the 1 m path due to gas flow from the ion source, that beam losses occur due to fringing fields at the entrance and exit of the guide, which could be prevented in an improved version, and that the defocussing potential caused by the space charge of the low-energy heavy-ion beam diminishes the critical glancing angle severely. With thermal electrons the ions beam cannot be charge-neutralized within the two-wire structure. (orig.)

[en] We experimentally studied the effect of an injection current on the Josephson current in a superconductor/two-dimensional electron gas/superconductor junction. The two-dimensional electron gas is realized by using an InGaAs/InP heterostructure while Nb is taken for the superconducting electrodes. The suppression of the Josephson supercurrent by injecting hot carriers from an additional Nb electrode is explained by the modification of the carrier distribution function. The differential conductance between the injector electrode and the Josephson junction is found to be enhanced if the junction is in the superconducting state. This effect is explained by an interference of the quasi-particles which are phase-coherently Andreev reflected between the superconducting junction electrodes. The dependence of this enhancement on an external magnetic field and on the injection current is studied in detail

No abstract available

[en] The purpose of this paper is to indicate techniques which have proven useful and to identify some typical pitfalls that should and can be avoided in order to prevent or minimize degradation of YBCO superconducting properties. No significant electrical damage was observed for YBCO linewidths as narrow as 1 μm. An example of results obtained using our process can be found. (orig.)

[en] The authors report on current-induced magnetization switching (CIMS) in single-crystalline nanopillars. Fe(14 nm)/Cr(0.9 nm)/Fe(10 nm)/Ag(6 nm)/Fe(2 nm) multilayers are deposited by molecular-beam epitaxy. The central Fe layer is coupled to the thick one by interlayer exchange coupling over Cr, while the topmost Fe layer is decoupled. Nanopillars with 150 nm diameter are prepared by optical and e-beam lithographies. The opposite spin scattering asymmetries of the Fe/Cr and Fe/Ag interfaces enabled the authors to observe normal and inverse CIMS for the two subsystems, which are combined in a single device. At high magnetic fields, steplike resistance changes are measured at positive currents and are attributed to current-driven magnetic excitations

[en] At synchrotron radiation sources, parabolic refractive x-ray lenses allow one to built both full field and scanning microscopes in the hard x-ray range. The latter microscope can be operated in transmission, fluorescence, and diffraction mode, giving chemical, elemental, and structural contrast. For scanning microscopy, a small and intensive microbeam is required. Parabolic refractive x-ray lenses with a focal distance in the centimeter range, so-called nanofocusing lenses (NFLs), can generate hard x-ray nanobeams in the range of 100 nm and below, even at short distances, i. e., 40 to 70 m from the source. Recently, a 47 x 55 nm2 beam with 1.7 · 108 ph/s at 21 keV (monochromatic, Si 111) was generated using silicon NFLs in crossed geometry at a distance of 47m from the undulator source at beamline ID13 of ESRF. This beam is not diffraction limited, and smaller beams may become available in the future. Lenses made of more transparent materials, such as boron or diamond, could yield an increase in flux of one order of magnitude and have a larger numerical aperture. For these NFLs, diffraction limits below 20 nm are conceivable. Using adiabatically focusing lenses, the diffraction limit can in principle be pushed below 5 nm

[en] Based on nanofocusing refractive x-ray lenses a hard x-ray scanning microscope is currently being developed and is being implemented at beamline ID13 of the European Synchrotron Radiation Facility (Grenoble, France). It can be operated in transmission, fluorescence, and diffraction mode. Tomographic scanning allows one to determine the inner structure of a specimen. In this device, a monochromatic (E=21 keV) hard x-ray nanobeam with a lateral extension of 47x55 nm² was generated. Further reduction of the beam size to below 20 nm is targeted

[en] The authors report on fabrication and measurement of traveling-wave photomixers based on high energy and low dose nitrogen-ion-implanted GaAs. They used 3 MeV energy to implant N⁺ ions into GaAs substrates with an ion concentration dose of 3x10¹² cm^-2. The N⁺-implanted GaAs photomixers exhibit improvements in the output power in comparison with their counterparts, photomixers fabricated on low-temperature-grown GaAs. The maximal output power was 2.64 μW at 850 GHz. No saturation of the output power with increased bias voltage and optical input power was observed. These characteristics make N⁺-implanted GaAs the material of choice for efficient high power sources of terahertz radiation