Electrochemical metallization memories--fundamentals, applications, prospects

This review focuses on electrochemical metallization memory cells (ECM), highlighting their advantages as the next generation memories. In a brief introduction, the basic switching mechanism of ECM cells is described and the historical development is sketched. In a second part, the full spectra of materials and material combinations used for memory device prototypes and for dedicated studies are presented. In a third part, the specific thermodynamics and kinetics of nanosized electrochemical cells are described. The overlapping of the space charge layers is found to be most relevant for the cell properties at rest. The major factors determining the functionality of the ECM cells are the electrode reaction and the transport kinetics. Depending on electrode and/or electrolyte material electron transfer, electro-crystallization or slow diffusion under strong electric fields can be rate determining. In the fourth part, the major device characteristics of ECM cells are explained. Emphasis is placed on switching speed, forming and SET/RESET voltage, R(ON) to R(OFF) ratio, endurance and retention, and scaling potentials. In the last part, circuit design aspects of ECM arrays are discussed, including the pros and cons of active and passive arrays. In the case of passive arrays, the fundamental sneak path problem is described and as well as a possible solution by two anti-serial (complementary) interconnected resistive switches per cell. Furthermore, the prospects of ECM with regard to further scalability and the ability for multi-bit data storage are addressed.     

UV‐assisted screen‐printing of flat textiles

An approach to printing of flat textiles is presented in this work. A screen‐printing method was applied on a cotton fabric. An aqueous printing paste was prepared from thickening and crosslinking agents and an ultraviolet‐sensitive tetrazole ring‐based compound of 2,3,5‐triphenyltetrazolium chloride or nitrotetrazolium blue chloride. After the printing process, a pattern was just visible with the naked eye. The development of colour occurred after exposure of the textile to ultraviolet light of 253.7 nm and was caused by the transformation of 2,3,5‐triphenyltetrazolium chloride or nitrotetrazolium blue chloride salts into the corresponding formazans, which are insoluble in water. The printed designs were resistant to washing. The stability of the colour of the samples is discussed in the case of prolonged irradiation, both with ultraviolet light of 253.7 nm and with daylight. This method of printing is a recent proposition for creative textile designing. It also seems to indicate a likely type of dye that may be further developed as potentially attractive for ultraviolet‐assisted printing or dyeing of textiles.     

Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.     

An Embeddable Multilevel-Cell Solid Electrolyte Memory Array

Nonvolatile memory cells based on solid electrolytes have many desirable attributes, including low-voltage and low-current operation and a simple process that allows them to be integrated with conventional CMOS processes with minimal additional masking layers. In this paper, we present a 2-kb memory block/testbed (1024 elements) using solid electrolyte cells. The compact memory design addresses many of the unusual operational issues associated with the solid electrolyte elements and allows for two digital bits to be stored and read from each cell with minimal circuitry. The design was fabricated in 0.18-mum CMOS technology and the simulation and physical data are presented. Multilevel-cell (MLC) operation was demonstrated for a 10-muA reference current with a 437-ns cycle time and sub-40-ns access times     

Geometric parameters for some flow channels

A method was proposed earlier⁽¹⁾ for prediction of the average velocity or pressure drop in the flow of non- Newtonian fluids in conduits of arbitrary cross section. The method requires only a knowledge of two geometric parameters which characterize the flow geometry, and the fluid model equation. In this paper, evaluations of geometric parameters are presented for infinite and finite (enclosed)square and triangular arrays of cylinders, and for regular polygonal and star-shaped conduits. With these parameters, predictions of the average velocity or related variables for the Zlow of any arbitrary non-Newtonian fluid can now be made. Comparisons are made with recent analytical solutions and experimental data pertaining to non-Newtonian flow in concentric annuli, and equilateral and right isosceles triangular ducts, which give additional support to the reliability of the proposed method.     

Characterization of polymer adsorption in tube flow of drag reducing fluids

Elucidation of the polymer adsorption and flow characteristics at the tube wall is essential for an understanding of turbulent drag reduction. The polymer adsorbed onto the tube wall, in the flow of dilute solutions of linear random coiling macromolecules, also produces a concentrated fluid layer at the surface of the adsorption zone, as a result of the flow of the solvent micromolecules in the porous network comprising the adsorption zone.Velocity profiles are developed and used to determine the radial variation in the adsorption zone of porosity, as well as fractional surface coverages and mean separation or interpenetration distances between macromolecules in the various adsorption layers. The polymer concentration build-up in the concentrated fluid layer is also evaluated. Predictions of the latter for aqueous Polyox WSR-301 solutions are in qualitative agreement with experimental measurements and suggest that turbulent drag reduction is related to the level of polymer build-up in the concentrated fluid layer.     

Low voltage cycling of programmable metallization cell memory devices

Future nanoscale memory technologies must ultimately be able to operate at power supply voltages in the order of 0.6 V or less. We have demonstrated in this work that it is possible to utilize symmetric program-erase (P-E) cycling for Ag/Ag-Ge-S/W programmable metallization cell devices at voltages below 0.6 V and still maintain an OFF/ON resistance ratio well in excess or 10 over a wide range of program and erase currents (0.27, 1.6, 55 and 220 μA) as set by a series resistance. The distributions of resistance values for 10(4) P-E cycles indicate that the margins between the highest on- and lowest off-state resistances are sufficient for unambiguous differentiation in all but the lowest current case in which there is some overlap. In addition, there is no substantial change in switching speed for up to 1.5 × 10(6) P-E operations, the maximum number of cycles attempted in this study.     

Minding the Gap: Central Bank Estimates of the Unemployment Natural Rate

A time-varying parameter framework is suggested for use with real-time multiperiod forecast data to estimate implied forecast equations. The framework is applied to historical briefing forecasts prepared for the Federal Open Market Committee to estimate the U.S. central bank's ex ante perceptions of the natural rate of unemployment. Relative to retrospective estimates, empirical results do not indicate severe underestimation of the natural rate of unemployment in the 1970s. Jel classification No: E3, E5, N1