Switching Time Measurement Research Articles

Unveiling the Resistive Switching Mechanism and Low Current Dynamics of Ru‐based Hybrid Synaptic Memristors

AbstractMobile Ru ions in oxide media have been reported as a novel species that offer extremely low switching currents for memristors. However, their bi‐stable resistive‐switching (RS) and low‐switching currents dynamics have not been quantitatively unveiled. Here, the bi‐stable RS mechanism via in‐depth field‐induced atomic migration and chemical bonding state studies is elucidated, showing that the RS of the Ru‐based hybrid memristor (RHM) is possible via the simultaneously controlled hybrid Ru cation and oxygen anion. Additionally, the Ru ion mobility is quantitatively obtained via atomic moving distance and switching time measurements, demonstrating that the lower Ru ion mobility, compared to other conventional mobile species in oxide media, can be the origin of the low‐switching currents. It is found that the current conduction mechanism of the low‐resistance‐state in RHMs has temperature‐range‐dependencies. The direct tunneling conduction mechanism is dominant in relatively low temperatures; however, the ionic transport and thermally activated hopping conduction mechanism govern the current flow in high temperatures. Owing to the low Ru ion mobility, the RHM exhibits highly linear synaptic plasticity with a low‐conductance regime, showing outstanding energy efficiency compared to other memristors in image recognition tasks. These findings can contribute to improving the feasibility of hyper‐scale synaptic cores consisting of RHMs.

Enhancement of electro-optical response of photonic crystal fibers infiltrated with ferroelectric liquid crystal doped with titanium dioxide nanoparticles.

Light propagation has been studied in photonic crystal fibers (PCFs) doped with W212 ferroelectric liquid crystal (FLC) composites with titanium dioxide nanoparticles (TiO2 NPs) of low concentrations between 0.2 and 1 wt. % in the FLC matrix. Optical microscopy observations indicated a slight increase of transition temperature to the isotropic phase by ∼1-2°C compared to the undoped FLC sample, and the TiO2 admixture was found to decrease free ionic charge impurities in the FLC, thus improving its electro-optical parameters. The switching time measurements in the PLCFs clearly indicate that TiO2 NPs reduce switching times for low electric field intensity, even by 32% compared to the undoped PLCF.

Investigation of Imprint in FE-HfO₂ and Its Recovery

Ferroelectric (FE)-HfO2-based FETs (FEFETs) are one of the most promising candidates for emerging memories. However, the FE material suffers from a unique reliability phenomenon known as imprint: the coercive voltage shifts during data retention, which has been regarded as a major issue for memory operation, while the mechanism causing it is still under research. In this article, imprint and its recovery in FE-HfO2 are investigated in detail by comprehensive electrical measurements to reveal its underlying mechanism including the cause of asymmetric coercive voltage shifts. The recovery measurements clarify that domain switching is indispensable for the recovery from imprint. The subloop imprint effect shows that imprint and its recovery must be independent for each domain. In addition, switching time measurements and corresponding fitting results with the nucleation-limited-switching (NLS) model strongly indicate that imprint is caused by domain-seeds-pinning. Based on these results, we conclude that charge trapping and detrapping affecting activation barriers for domain switching, accompanied by domain switching, is responsible for imprint and its recovery.

Mechanical Stress Dependence of the Switching Field in Amorphous Microwires

Glass-coated magnetic microwires belong to a unique rank among materials that have high potential to be used in new technologies. We have studied the possibility to employ amorphous bistable microwires as a sensor for bending of carbon fiber composite. The measurement of switching time instead of switching field drastically increases the sensitivity of such sensors up to 380% for positive bending and 125% for negative bending. The results show that microwires applied on the surface structures of the materials can be used as sensors of mechanical stresses or bending.

Method of Measuring the Switching Time of Dual Redundant NIC

In this paper, the authors present a method of measuring the switching time of a dual redundant NIC. The accuracy of the authors’ method of measuring switching time can reach milliseconds. The authors’ method uses Internet Control Message Protocol (ICMP) packets to test, is easy to operate, has high precision, and can be applied to all types of dual redundant device switching time measurement.

Piezoelectric unimorph valve assembled on an LTCC substrate

In this paper a piezoelectric initially open valve was designed in low temperature co-fired ceramic (LTCC), manufactured using standard processes, and tested with integrated gas channels inside the LTCC module. Actuation of the valve was based on a piezoelectric unimorph with a diameter of 15 mm and thickness of 0.35 mm glued onto the fired LTCC substrate. Subsequently, a series of tests, including flow, displacement and switching time measurements, was carried out. Measurements of the valve revealed a flow of 143 ml/min under 1 bar pressure, leakage levels of 4%, valve displacement of 1.3 μm, and closing times less than 30 ms. Additional miniaturization and integration of an embedded valve in the LTCC will be pursued, enabling improved manufacturing as a batch process and micro- and nano-litre fluid management for various applications.

The electrochromic behavior of nickel oxide films sprayed at different preparative conditions

Nickel oxide films have been prepared onto transparent conducting-coated glass at different substrate temperatures using spray pyrolysis technique. Electrochromic characterizations of the prepared films have been studied by cycling between their coloured and bleached states using a three-electrode cell containing 1 M KOH electrolyte. The influence of substrate temperature as well as film thickness on the electrochromic (EC) performance has been investigated. The substrate temperature ( T sub), film thickness, and the colouration and bleaching potentials have been optimized as 275 °C, 140 nm, +0.7 and −1.0 V, respectively. With optimized coating and working parameters, the results yielded transmission solar modulation Δ T s=0.35, visible modulation Δ T v=0.51, injected charge=14 mC and colouration efficiency η=44 cm 2/C. In addition to the nominal bleaching state, a full bleaching state is newly assigned leading to higher optical modulation of 0.45 and 0.63 for Δ T s and Δ T v, respectively. An adequate potential pulse shape is suggested for operating the device. Different from some reported results, switching time measurements showed that colouration is faster than bleaching which may obscure different redox mechanisms of EC colouration. Infrared reflectance spectroscopy showed evidently the significance of water in the EC process. The results showed clear consistency with the view that a transparent film of Ni(OH) 2 is made absorbing through transformation to coloured NiOOH. Discussion of the results supports the colouration mechanism of double extraction of proton and electron.

Micro-optical 1 x 4 fiber switch for multimode fibers with 600-microm core diameters.

The design, manufacture, and test of a 1 x 4 micro-optical fiber switch for multimode fibers with 600-microm core diameters are described. Microlens array telescopes allow for variable and fast beam deflection when the positions of the cylindrical microlens arrays relative to each another are altered by specially designed piezomechanical actuators. Standard achromats are used for collimation of light emitted by the input multimode fiber and for focusing of the deflected light onto a linear array of output multimode fibers. Design and assembly of micro-optical as well as of optomechanical components are discussed. Insertion loss and cross talk are measured, and the results are compared with those of numerical optical simulations. Measurements of switching time and long-term stability, as well as of thermal behavior, are also presented.

Switching time measurements of current-induced magnetization reversal

Electrical contacts to single isolated nickel nanowires (80 nm in diameter, 6000 nm in length), pulsed current densities of about 10/sup 7/ A/cm/sup 2/ and a Wheatstone bridge of a 1 GHz bandwidth allow detection of the magnetization switching in static magnetic fields. The temperature of the nanowires during the current pulse is deduced from their resistance change. The measurements of switching time as a function of applied field and current demonstrate that the current lowers the energy barrier for switching.

Dynamical measurement of domain-wall nucleation and annihilation in individual amorphous Co particles.

We present magnetization measurements of individual amorphous Co particles (300 nm\ifmmode\times\else\texttimes\fi{}200 nm\ifmmode\times\else\texttimes\fi{}30 nm) patterned by electron-beam lithography. The hysteresis loops show mainly two magnetization jumps corresponding to domain-wall nucleation and annihilation. The angular dependence of these magnetization jumps is measured and the temperature dependence (0.1--6 K) of the nucleation and the annihilation processes is investigated by two independent methods: switching field and switching time measurements. Finally we compare the results obtained on one particle with those of an array of about 2\ifmmode\times\else\texttimes\fi{}${10}^{7}$ particles. We show experimentally that the dynamical properties measured on individual particles are connected with an unusual 1/T relaxation of the array of particles. \textcopyright{} 1996 The American Physical Society.

Picosecond switching time measurement of a resonant tunneling diode

Picosecond bistable operation has been experimentally observed for the first time in a double-barrier resonant tunneling diode. A rise time of 2 ps was measured using the electro-optic sampling technique; this is the fastest switching event yet observed for an electronic device. This time domain measurement adds necessary information to the understanding of the transport mechanisms in the resonant tunneling diode and is consistent with switching time limitations computed for the device. It also demonstrates that appropriately designed double-barrier quantum well diodes have a response time comparable to that of the fastest all-optical logic elements, and that they may be very useful in high-speed logic applications.

The interaction potential between discommensurations in Rb2ZnCl4–the existence of a bistable polar state

Abstract The measurements of switching time in Rb2ZnCl4 type crystals show that the sideways motion of the discommensurations is a dominant mechanism in the polarization reversal process. The measurement of the dielectric constant within the commensurate phase as a function of the bias electric field enables a direct observation of the interaction potential between discommensurations. These results indicate that the exponential interaction changes to an oscillatoric one at T ∼ 150 K.

The electrical properties of bistable niobium pentoxide films

Current, voltage, temperature ( I - V - T ) and conductance, voltage, temperature ( G - V - T ) as well as switching time measurements have been made on the switching states of bistable amorphous niobium pentoxide films. The measurements are indicative of a charge transfer mechanism occurring prior to switching. I - V - T and G - V - T measurements on the switching states for temperatures in the range 1.3 to 4.2°K as well as at 77°K are discussed.

Some methods of switching time measurement of ferromagnetic cores

Some methods of switching time measurement of ferromagnetic cores

Magnetic domain wall mobility limitation by anisotropic impurity ions in ferrimagnetic insulators

A theory is given for the limitation of magnetic domain wall velocity in ferrimagnetic insulators due to the relaxation of constituent ions with anisotropic energy levels. For 10 per cent Yb 3+ doped yttrium iron garnet the predicted velocity falls from 7 × 10 5 cm sec −1 Oe −1 at 300°K to 20 cm sec −1 Oe −1 at ∼ 12°K, then rises sharply. Measurements of switching time on pure and 10 per cent doped Yb doped Y.I.G. show the impurity dominates the velocity limitation for 6°K < T < 100°K and experiment accords with theory here within the limits of the qualitative comparison. According to the theory the phenomenological damping constant determined from microwave resonance line-width and wall velocity are predicted to agree, roughly, for high but not low T for such materials. The low wall velocity observed in pure Y.I.G. receives no explanation.

A Description of Magnetic Switching in Disperse Anisotropy Films

The model of a magnetic film as one domain with a single anisotropy axis is often an inadequate approximation to true film behavior. A better approximation considers the film to consist of many uniaxial regions, with a range of anisotropy constants and of axis orientations in the plane of the film. The dispersion of values results in considerable confusion and awkwardness when using the single domain representation to understand magnetic switching. It is shown here that the total anisotropy distribution can be displayed on a polar plot in which each film region is characterized by a single point with the coordinates: Hk, its anisotropy field, and α, its axis orientation. In this (Hk,α) plane the switching effectiveness of the applied field is represented by a curve which is fixed in size and orientation relative to the field vector. Switching occurs in those parts of the film whose anisotropy points fall within the curve. The field figure is extended to include magnetization reversal by domain wall motion. Inverted switching behavior and switching time measurements are briefly discussed. Interactions between regions are not considered.