Application of an electron backscatter diffraction pattern to Cu damascene-fabricated interconnections filled by a high-pressure anneal process

The microstructure of Cu interconnections fabricated by high-pressure annealing was evaluated using a field emission scanning electron microscope/electron backscatter diffraction pattern (FE-SEM/EBSP) technique, and the results are compared with as-deposited and normally annealed Cu films. The results show some grains extending from the bulk field to the via regions in the case of the high-pressure annealed Cu films. The existence of via holes was also observed, in which all grains were (111) oriented. This indicates that the high-pressure annealing process enables the Cu that in-fills the via holes to develop into favorable microstructures, i.e., single-crystal and with (111) orientation.     

A Reliable All-2D Materials Artificial Synapse for High Energy-Efficient Neuromorphic Computing

High-performance artificial synaptic devices are indispensable for developing neuromorphic computing systems with high energy efficiency. However, the reliability and variability issues of existing devices such as nonlinear and asymmetric weight update are the major hurdles in their practical applications for energy-efficient neuromorphic computing. Here, a two-terminal floating-gate memory (2TFGM) based artificial synapse built from all-2D van der Waals materials is reported. The 2TFGM synaptic device exhibits excellent linear and symmetric weight update characteristics with high reliability and tunability. In particular, the high linearity and symmetric synaptic weight realized by simple programming with identical pulses can eliminate the additional latency and power consumption caused by the peripheral circuit design and achieve an ultralow energy consumption for the synapses in the neural network implementation. A large number of states up to ≈3000, high switching speed of 40 ns and low energy consumption of 18 fJ for a single pulse have been demonstrated experimentally. A high classification accuracy up to 97.7% (close to the software baseline of 98%) has been achieved in the Modified National Institute of Standards and Technology (MNIST) simulations based on the experimental data. These results demonstrate the potential of all-2D 2TFGM for high-speed and low-power neuromorphic computing.     

Block Copolymer Permeable Membrane with Visualized High‐Density Straight Channels of Poly(ethylene oxide)

A simple fabrication, scalable to centimeter scale, of a permeable membrane made of block copolymer containing molecular transport channels is demonstrated by coating photo‐crosslinkable liquid‐crystalline block copolymer, consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) bearing stilbene (Stb) mesogens in the side chains (PEO₁₁₄‐b‐PMA(Stb)₅₂), onto a sacrificial cellulose acetate film substrate. After thermal annealing, perpendicularly aligned and hexagonally arranged PEO cylindrical domains with a surface density of 10¹¹ cm^?2 were formed and then fixed efficiently by photo‐crosslinking the stilbene moieties in the PMA(Stb) domains by [2 + 2] dimerization. The fully penetrating straight PEO cylindrical domains across the 480‐nm‐thick membrane were well‐defined and visualized as molecule‐transport channels. After exfoliated by removal of the cellulose acetate layer, the membrane could be transferred onto another substrate by either scooping or a horizontal lifting method. Throughout the processes, the fully penetrating PEO channels across the membrane are preserved to open at both ends. A simple permeation experiment demonstrates that rhodamine dyes permeate efficiently through the PEO cylindrical channels of the annealed membrane but not across a non‐annealed one.     

Fabrication of carbon nanofibers using only ion beam irradiation to glassy carbon

Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are new carbon-based materials. However, the production of CNFs and CNTs is very difficult due to the complicated processes and high temperature involved. Therefore, a method of fabrication is required that enables high throughput at a low cost.Our previous study reported that oxygen ion beam energy of 500 eV applied to glassy carbon (GC) forms the finest pitch conical anti-reflection (AR) structures, and that an irradiation time of more than 24 min fabricates conical AR structures with heights of more than 250 nm. After the fabrication of the AR structures, irradiation by an argon ion (Ar⁺ beam changes the surface morphology, and oblique angle irradiation can form CNFs. Thus, we carried out oblique Ar⁺ beam irradiation on conical carbon protrusions on GC fabricated by oxygen ion beam irradiation. As a result, CNFs have been formed using oxygen and argon ion beam irradiation at room temperature. In addition, multi-wall CNT can be obtained by two-step ion beam irradiation.     

In-Plane Coupling of Light From InP-Based Photonic Crystal Band-Edge Lasers Into Single-Mode Waveguides

In this paper, we analyze the coupling of light from photonic-crystal band-edge lasers into single-mode waveguides. Both active and passive devices lie in the same plane and coupling of light is achieved by using parabolic and nanotapers in InP based epitaxial structures. Two- and three-dimensional finite-difference time-domain methods are employed to analyze these devices. Coupling efficiencies higher than 80% can be obtained with parabolic couplers. We also present laser configurations that can reduce multiwavelength coupling of light into single-mode waveguides, using structures that are similar to coupled cavity Fabry-Peacuterot lasers     

Development of a 385–500 GHz Sideband-Separating Balanced SIS Mixer

A submillimeter (385–500 GHz) low-noise sideband-separating balanced SIS (Superconductor Insulator Superconductor) mixer (Balanced 2SB mixer) with high IRR (Image Rejection Ratio) has been successfully developed, whose SSB (Single SideBand) noise temperature is ～ 200 K (10hf/k) with an image rejection ratio of ≥?～10 dB. Balanced mixers have become a promising technology which would break through the limitation especially in terahertz receivers and heterodyne arrays. However, though there are examples in microwave with relatively worse noise performance, submillimeter and terahertz balanced mixers have rarely been developed in spite of their astronomical importance. The developed balanced 2SB mixer is not only the first one demonstrated at submillimeter frequency range, but also has very low noise, high IRR, wide detectable frequencies (385–500 GHz), and a flat IF output spectrum. The balanced 2SB mixer is composed of three RF hybrids, four DSB (Double SideBand) mixers, two 180° IF hybrids, and an IF quadrature hybrid. Several important performance indicators such as noise temperature, IRR, required LO (Local Oscillator) power, and IF spectra were measured. The measured LO power required for the balanced 2SB mixer was typically ~ 14 dB less than that of the single-ended mixers.     

Use of support vector regression and numerically predicted cloudiness to forecast power output of a photovoltaic power plant in Kitakyushu,Japan

The development of a methodology to forecast accurately the power produced by photovoltaic systems can be an important tool for the dissemination and integration of such systems on the public electricity grids. Thus, the objective of this study was to forecast the power production of a 1‐MW photovoltaic power plant in Kitakyushu, Japan, using a new methodology based on support vector machines and on the use of several numerically predicted weather variables, including cloudiness. Hourly forecasts of the power produced for 1 year were carried out. Moreover, the effect of the use of numerically predicted cloudiness on the quality of the forecasts was also investigated. The forecasts of power production obtained with the proposed methodology had a root mean square error of 0.0948 MW h and a mean absolute error of 0.058 MW h. It was also found that the forecast and measured values of power production had a good level of correlation varying from 0.8 to 0.88 according to the season of the year. Finally, the use of numerically predicted cloudiness had an important role in the accuracy of the forecasts, and when cloudiness was not used, the root mean square error of the forecasts increased more than 32%, and the mean absolute error increased more than 42%. Copyright © 2011 John Wiley & Sons, Ltd.     

Observation of polarization property in near-field optical imaging by a polarization-maintaining fiber probe

We fabricated an original near-field scanning optical microscopy (NSOM) fiber probe made of polarization-maintaining and attenuation-reducing (PANDA)-type polarization-maintaining optical fiber, and observed the polarization property of propagation light in a polymer optical waveguide. The distribution of the transmission coefficient in polarization angles through this NSOM probe showed that the linear polarization is maintained in the two crossing directions: the fast and slow axes. The polarization degree parallel to the slow axis decreases from 1000:1 to 2:1 by bending the fiber probe and the decrease is independent of the bending direction. Using this PANDA-type NSOM probe, we investigated the polarization property of periodic intensity modulation. It was found that the intensity modulation was observed clearly with the electric vector parallel to the radius direction of the waveguide, but was observed vaguely with the electric vector perpendicular to the radius direction.     

Characterization,Cathodoluminescence, and Field‐Emission Properties of Morphology‐Tunable CdS Micro/Nanostructures

High‐quality, uniform one‐dimensional CdS micro/nanostructures with different morphologies—microrods, sub‐microwires and nanotips—are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field‐emission properties are systematically investigated. Microrods and nanotips exhibit sharp near‐band‐edge emission and broad deep‐level emission, whereas sub‐microwires show only the deep‐level emission. A significant decrease in a deep‐level/near‐band‐edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high‐resolution transmission electron microscopy. Field‐emission measurements show that the nanotips possess the best field‐emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn‐on field of 5.28 V µm^?1 and the highest field‐enhancement factor of 4 819. The field‐enhancement factor, turn‐on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.     

Design of zero-phase recursive 2-D variable filters with quadrantal symmetries

The digital filters with adjustable frequency-domain characteristics are called variable filters. Variable filters are useful in the applications where the filter characteristics are needed to be changeable during the course of signal processing. In such cases, if the existing traditional constant filter design techniques are applied to the design of new filters to satisfy the new desired characteristics when necessary, it will take a huge amount of design time. So it is desirable to have an efficient method which can fast obtain the new desired frequency-domain characteristics. Generally speaking, the frequency-domain characteristics of variable filters are determined by a set of spectral parameters such as cutoff frequency, transition bandwidth and passband width. Therefore, the characteristics of variable filters are the multi-dimensional (M-D) functions of such spectral parameters. This paper proposes an efficient technique which simplifies the difficult problem of designing a 2-D variable filter with quadrantally symmetric magnitude characteristics as the simple one that only needs the normal one-dimensional (1-D) constant digital filter designs and 1-D polynomial approximations. In applying such 2-D variable filters, only varying the part of 1-D polynomials can easily obtain new desired frequency-domain characteristics.