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[en] The specification discloses a process for forming a superconductor/semiconductor junction structure having optimized low-temperature current transport properties by first providing a substrate of a chosen semiconductor material having an atomically clean surface. A layer of a first chosen superconducting material is deposited on or above the surface of the substrate to a predetermined thickness. Either before or after the formation of this layer of the first superconducting material, a region of a second chosen superconducting material is formed between the surface of the substrate and the layer of the first superconducting material to serve as an interfacial reaction barrier to prevent the reaction between the surface of the substrate and the first chosen superconducting material at the interface thereof which would otherwise result in the formation of an undesired non-superconducting material at the interface. By preventing this undesired interfacial reaction, an optimized low-temperature current transport path is maintained across the interface and certain device performance characteristics can be optimized. Josephson junction superconducting devices and super-Schottky devices may be formed by this disclosed process
[en] Cross-bar arrays are usually used for the high density application of resistive random access memory (RRAM) devices. However, cross-talk interference limits an increase in the integration density. In this paper, the Zener diode is proposed as a selection device to suppress the sneak current in bipolar RRAM arrays. Measurement results show that the Zener diode can act as a good selection device, and the sneak current can be effectively suppressed. The readout margin is sufficiently improved compared to that obtained without the selection device. Due to the improvement for the reading disturbance, the size of the cross-bar array can be enhanced to more than 103 × 103. Furthermore, the possibility of using a write-once-read-many-times (WORM) cross-bar array is also demonstrated by connecting the Zener diode and the bipolar RRAM in series. These results strongly suggest that using a Zener diode as a selection device opens up great opportunities to realize high density bipolar RRAM arrays. (paper)
[en] We describe a portable instrument that measures the average luminance coefficient of a road surface, Q0, in the field. The design employs a modified integrating hemisphere with light-emitting diode lamps as light sources and a calibrated charge-coupled device luminance meter with an observation angle of 1° as the detector. The diameter and weight of the hemisphere are 50 cm and approximately 8 kg, respectively. After first demonstrating proof of concept of the instrument, we calibrated the prototype with two methods and evaluated the performance by comparing its measurement results with those obtained by a gonioreflectometer for a series of samples. The performance characteristics of the instrument are appropriate for in situ Q0 measurement. (paper)
[en] The experimental results on the performance of the extruded scintillator and WLS fiber, and various LEDs in the magnetic fields of 1.8T and 2.3T respectively, are reported. The methodic used is being described
[en] The electrical switching in solid compositions based on chalcogenide materials is discussed. Different mechanisms proposed for switching effect are reviewed. A new description of the switching phenomenon is done. The switching is regarded as due to formation and breaking of the links between the dendrites of crystalline nuclei in bulk materials, as a consequence of the energy pumped by an electrical field. This mechanism explains the very short switching time (<20ns), the possibility to get smart memories based on multisteps of resistivity and the high number of cycles supported by the cell (1016).
[en] In this paper, the generation of short electrical pulses based on nonlinear active wave propagation effects along the resonant tunneling diode transmission line is studied. The principle of operation is discussed and it is shown by computer experiments that an input rectangular pulse as well as a sinusoidal input signal can be converted into a set of output spikes, suitable for A/D conversion at millimeter wave frequencies.
[en] Photonic structures are artificial materials whose dielectric constant is periodically-modulated in one, two or three dimensions. In a manner analogous to the creation of electronic bands, electromagnetic waves propagating in the structure are organized into photonic bands, which are separated by bandgaps where propagating states are forbidden. Spontaneous emission is suppressed for photons inside the photonic bandgap, offering novel approaches to creating high-efficiency light-emitting structures. The objective of this thesis is to assess a broad range of issues concerning the use of photonic structures in light-emitting devices based on GaAs. A comprehensive review was undertaken to identify the most suitable techniques for modelling, fabrication and experimental assessment of photonic structures in this context. The key results are: (1) The most appropriate method for calculating photonic band structure is the plane wave method, which was used with real-world values for the dielectric constant to identify appropriate dimensions for prototype structures. However the transfer matrix method is better for calculating the transmission and reflection coefficients, which are quantities that can be compared directly with experimental results. Software was written to extend this method to structures with hexagonal symmetry. (2) Electron beam lithography and electron cyclotron plasma etching were used to fabricate two-dimensional photonic structures in GaAs-based materials. Highly-uniform structures were produced over areas up to 200 μm2, and with feature sizes down to 50nm. This etching technique, which uses low energy ions, is particularly suited to device processing because it causes less etch damage. Other structures reported in the literature have used high-energy etch processes. (3) An experimental setup was developed to measure the transmission and reflection through a photonic structure etched into a waveguide. The technique, which uses a broadband light source to provide a wide spectral range, should allow the observation of both band edges on the same sample - this has not been achieved in any reported measurements. (author)