RETURN ON INVESTMENT IN SOCIAL NETWORKS

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

A Novel Nanoionics-Based Switch for Microwave Applications

This paper reports the development and characterization of a novel switching device for use in microwave systems. The device utilizes a switching mechanism based on nanoionics, in which mobile ions within a solid electrolyte undergo an electrochemical process to form and remove a conductive metallic "bridge" to define the change of state. The nanoionics-based switch has demonstrated an insertion loss of approx.0.5dB, isolation of >30dB, low voltage operation (1V), low power (approx. micro-W) and low energy (approx. nJ) consumption, and excellent linearity up to 6 GHz. The switch requires fewer bias operations (due to non-volatile nature) and has a simple planar geometry allowing for novel device structures and easy integration into microwave power distribution circuits

Metasurface-based Mueller Matrix Microscope

In conventional optical microscopes, image contrast of objects mainly results from the differences in light intensity and/or color. Muller matrix optical microscopes (MMMs), on the other hand, can provide significantly enhanced image contrast and rich information about objects by analyzing their interactions with polarized light. However, state-of-art MMMs are fundamentally limited by bulky and slow polarization state generators and analyzers. Here, we demonstrated the feasibility of applying metasurfaces to enable a fast and compact MMM, i.e., Meta-MMM. We developed a dual-color MMM, in both reflection and transmission modes, based on a chip-integrated high-speed (>20fps) metasurface polarization state analyzer (Meta-PSA) and realized high measurement accuracy for Muller matrix (MM) imaging. We then applied our Meta-MMM to nanostructure characterization, surface morphology analysis and discovered birefringent structures in honeybee wings. Our meta-MMMs hold the promise to revolutionize various applications from biological imaging, medical diagnosis, material characterization to industry inspection and space exploration

Fiscal Policy, Trigger Points and Interest Rates: Additional Evidence From the U.S.

We empirically investigate whether the relationship between interest rates and public deficits/debt may be nonlinear for the U.S. Using threshold estimation, we find evidence of level-dependent effects on interest rates, implying a significant effect of projected deficits and debt in the U.S. only if the deficit surpasses approximately 5% of GDP

Cation-based resistance change memory

A potential replacement for current charge-based memory technologies in the nanoscale device regime is a form of resistance change memory (RRAM) which utilizes cation transport and redox reactions to form and remove a conducting filament in a metal–electrolyte/insulator–metal (MEM/MIM) structure. A variety of oxide and higher chalcogenide materials have been used as the silver or copper ion transport medium, yielding devices with similar switching characteristics. The technology has been the subject of extensive research in academia and industry and is in an advanced stage of commercialization but there remain a number of fundamental questions regarding the fine details of device operation and the connection with electrochemical theory at the nanoscale. This review surveys some of the published research in the area and considers the topics of ion-conducting materials, rate limiting steps during device operation and filament stability. Device performance and modelling are also presented and discussed

Ultra-low Current Resistive Memory Based on Cu-SiO<inf>2</inf>

Ultra-low current resistive switching in sputtered Cu/SiO2/Pt and Cu/SiO2/Ir structures was investigated. Both Cu and SiO2 are commonplace in silicon integrated circuits and hence the material system is CMOS compatible. The switching characteristics were very similar to those observed in other solid electrolytes so that the mechanism is assumed to be the same, i.e., based on the formation and rupture of a nanoscale Cu filament. The first current voltage sweep serves as a forming step with write currents as low as 10nA. In the subsequent cycles, the write currents could be reduced to as little as 10pA, making this technology an ideal candidate for energy-starved applications. The switching voltage scaled with the delay time of the current-voltage sweep

Hearing Aid Sensitivity Optimization on Dual MEMS Microphones Using Nano-Electrodeposits

We present an in-situ sensitivity tuning method for MEMS (micro-electromechanical systems) microphones via the growth/retraction of nano-electrodeposits to achieve high directionality in hearing aid applications. Nano-electrodeposits are electrochemically grown and dissolved on an Ag-doped Ge-Se solid electrolyte film on a microphone diaphragm using a DC bias at room temperature. The growth and retraction of the nano-electrodeposits generate mass/stress redistribution on the diaphragm, tuning the microphone sensitivity to incoming acoustic sources. Acoustic measurements demonstrate that the directional microphone can achieve a 1.3 dB Directivity Index (DI) improvement upon nano-electrodeposit growth and 0.9 dB DI reversal on nano-electrodeposit retraction