Subnanosecond Switching Research Articles

High-Voltage Spark Gap in a Regime of Subnanosecond Switching

This paper describes an investigation of a high-voltage spark gap in the conditions of subnanosecond switching. The high-voltage pulsed generator “Sinus” is used to charge a coaxial line loaded to a high-pressure spark gap. Typical charging time for the coaxial line is in a range from 1 to 2 ns, maximum charging voltage is up to 250 kV, and a range of pressures for the gap is from 2 to 9 MPa. The theoretical models of the switching process on subnanosecond time scale are examined. A general equation for temporal behavior of the gap voltage, which is applicable for the avalanche model and the Rompe-Weitzel model has been obtained. It is revealed that the approach based on the avalanche model offers a possibility to describe the switching process only at extremely high overvoltages. The Rompe-Weitzel model demonstrates a good agreement with the experimental data both for the conditions of static breakdown and for the regime of a high overvolted gap. Comparison of experimental and calculated voltage waveforms has made it possible to estimate an empirical constant in the Rompe-Weitzel model (the price of ionization). This constant is varied from 420 to 920 eV, depending on the initial electric field in the gap.

Momentary interruption of current passing through zero in subnanosecond high-pressure gas-discharge switches

Data are reported for the performance of subnanosecond high-pressure gas-discharge switches aimed at generating high-voltage bipolar voltage pulses with a width of less than 1 ns, an amplitude of up to 200 kV, and a repetition rate of 100 Hz. Pulse formers, in which the polarity of the current passing through the switch does not change in the course of switching, seem to be the most appropriate. When the current changes sign, passing through zero, the effect of its momentary interruption is observed. The explanation of this effect is that, when the voltage across the gap reverses, a certain time interval is necessary for a cathode layer to form, which can transmit a high discharge current at a low voltage drop across the layer.

Precessional spin-transfer switching in a magnetic tunnel junction with a synthetic antiferromagnetic perpendicular polarizer

This paper reports sub-nanosecond precessional spin-transfer switching in elliptical magnetic tunnel junction nanopillars. This result is obtained in samples integrating a synthetic antiferromagnetic perpendicular polarizer and a tunnel junction with in-plane magnetized electrodes. The out-of-plane precession of the free layer magnetization results in oscillations of the switching probability as a function of the pulse width. At 9.25 MA/cm2 current density, these oscillations have a period of 1 ns with a high degree of coherence.

Continuous Electrical Tuning of the Chemical Composition of TaOx-Based Memristors

TaO(x)-based memristors have recently demonstrated both subnanosecond resistance switching speeds and very high write/erase switching endurance. Here we show that the physical state variable that enables these properties is the oxygen concentration in a conduction channel, based on the measurement of the thermal coefficient of resistance of different TaO(x) memristor states and a set of reference Ta-O films of known composition. The continuous electrical tunability of the oxygen concentration in the channel, with a resolution of a few percent, was demonstrated by controlling the write currents with a one transistor-one memristor (1T1M) circuit. This study demonstrates that solid-state chemical kinetics is important for the determination of the electrical characteristics of this relatively new class of device.

Ultrafast Low-Loss 40–70 GHz SPST Switch

The design and characterizations of an ultrafast single-pole single-throw (SPST) absorptive differential switch are presented. The switch exhibits low insertion loss less than 1 dB, and isolation better than 16 dB from 40 to 70 GHz. Sub-nanosecond switching time is achieved by adopting a differential current-steering technique. The total measured rise and fall time are 75 ps envisaging that switching rates up to 13 Gb/s are achievable. To our best knowledge, this is the fastest, lowest insertion loss V-band SPST switch yet reported that can operate over a wide bandwidth of 30 GHz.

Sub-nanosecond switching of a tantalum oxide memristor

We report sub-nanosecond switching of a metal–oxide–metal memristor utilizing abroadband 20 GHz experimental setup developed to observe fast switching dynamics. Setand reset operations were successfully performed in the tantalum oxide memristorusing pulses with durations of 105 and 120 ps, respectively. Reproducibility of thesub-nanosecond switching was also confirmed as the device switched over consecutivecycles.

Sub-nanosecond switching and acceleration to relativistic energies of field emission electron bunches from metallic nano-tips

The authors explore the generation of short electron bunches from a field-emitter array cathode consisting of nanometer-sized metallic tips that is compatible with an acceleration electric field above 10 MV/m. Sub-nanosecond field emission electron bunches were generated by applying fast electrical pulses to an on-chip electron extraction gate electrode of the cathode. The subsequent acceleration of the field emission electron bunches to 5 MeV was demonstrated using the combined diode-RF cavity SwissFEL electron gun test facility.

Resistance switching for RRAM applications

Resistive random access memory (RRAM or ReRAM) is a non-volatile memory (NVM) technology that consumes minimal energy while offering sub-nanosecond switching. In addition, the data stability against high temperature and cycling wear is very robust, allowing new NVM applications in a variety of markets (automotive, embedded, storage, RAM). Based on sudden conduction through oxide insulators, the characteristics of RRAM technology have still yet to be fully described. In this paper, we present our current understanding of this very promising technology.

高压氢气亚纳秒开关击穿特性

高压氢气亚纳秒开关击穿特性

Sub-nanosecond optical switch based on silicon racetrack resonator

We experimentally demonstrate a small-size and high-speed silicon optical switch based on the free carrier plasma dispersion in silicon. Using an embedded racetrack resonator with a quality factor of 7400, the optical switch shows an extinction ratio exceeding 13 dB with a footprint of only 2.2×10−3 mm2. Moreover, a novel pre-emphasis technique is introduced to improve the optical response performance and the rise and the fall times are reduced down to 0.24 ns and 0.42 ns respectively, which are 25% and 44% lower than those without the pre-emphasis.

Switching avalanche S-diodes based on GaAs multilayer structures

Results of studying volt-ampere characteristics of switching avalanche S-diodes are presented. It is shown that, for S-diodes based on structures obtained by diffusing Cr into GaAs, a larger part of the applied reverse-biased voltage drops across a high-resistance π-region but not across the space-charge region. In this case, the sharp increase of the current is caused by the electron injection from the forward-biased contact to the π-layer. In this respect, a new GaAs-based structure doped with Cr and Fe (GaAs:Cr, Fe) is studied. It is shown that, in S-diodes based on (GaAs:Cr, Fe)-structures, the current increase under a reverse bias is caused by avalanche processes in the space-charge area. This leads to producing a negative differential resistance section with subnanosecond switching from the closed to open state. The switching voltages of S-diodes on GaAs:Cr, Fe structures vary from 350 to 650 V, and the switching times do not exceed 0.5 ns.

Reproducible trajectory on subnanosecond spin-torque magnetization switching under a zero-bias field for MgO-based ferromagnetic tunnel junctions

One of the features of spin-transfer torque (STT)-based magnetic random access memories (spin-RAMs) is a fast write cycle; however, switching properties in the subnanosecond regime for MgO-based magnetic tunnel junctions (MTJs) are still unclear. In this work, we demonstrated subnanosecond magnetization switching by STT for MgO-based MTJs. We also discuss the thermal effect on subnanosecond STT switching, as well as the subnanosecond pulse width that is dependent on the remarkable plateau that switching probability has under a zero-bias field.

Energy dissipation and transport in nanoscale devices

Understanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. This review presents recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures. First, the landscape of power usage from nanoscale transistors (∼10−8 W) to massive data centers (∼109 W) is surveyed. Then, focus is given to energy dissipation in nanoscale circuits, silicon transistors, carbon nanostructures, and semiconductor nanowires. Concepts of steady-state and transient thermal transport are also reviewed in the context of nanoscale devices with sub-nanosecond switching times. Finally, recent directions regarding energy transport are reviewed, including electrical and thermal conductivity of nanostructures, thermal rectification, and the role of ubiquitous material interfaces.

Sub-nanosecond silicon-on-insulator optical micro-ring switch with low crosstalk

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator (SOI) dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20-mu m-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of < 400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor (CMOS) compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

Microwave-assisted switching of NiFe magnetic microstructures

We have calculated, by either macrospin analytical method or micromagnetic numerical solving, the microwave assisted switching of a small rectangular platelet as a function of the amplitude and the frequency of a microwave excitation field. The spectral analysis of this phenomenon reveals that microwave-assisted switching is optimal for a rf frequency slightly lower than the linear magnetic resonance frequency measured at low level. Similar experimental results, obtained on 100 μm-scale NiFe structures reveal the same tendency. Switching time for such a process was obtained from calculations that show that sub-nanosecond switching times require combinations of large dc (direct current) and rf (radio frequency) magnetic fields.

Magnetization reversal by a single pulse of magnetic field or spin-polarized current

One of the important requirements for spintronic devices concerns an efficient magnetization reversal, which may eventually lead to ultra-fast non-volatile magnetic memory applications. In particular, it is necessary to achieve stable sub-nanosecond switching times and to reduce magnetization “ringing”, so that the reversal will proceed along the shortest ballistic path connecting the initial and the target magnetization states. This paper is dedicated to the numerical simulations of a mono-domain ferromagnetic particle, described by the Landau–Lifshitz–Gilbert equation. We study the general case of arbitrary orientation of the applied field/current pulses, constructing dynamic diagrams for the reversal time. We have found that even short 50 ps pulses, applied at a proper angle, will induce magnetization reversal with minimal ringing effects.

Microwave-assisted switching of NiFe magnetic microstructures

We have calculated by either macrospin analytical method or micromagnetic numerical solving the microwave-assisted switching of a small rectangular platelet as a function of the amplitude and the frequency of a microwave excitation field. The spectral analysis of this phenomenon reveals that microwave-assisted switching is optimal for a rf slightly lower than the linear magnetic resonance frequency measured at low level. Similar experimental results, obtained on 100 μm scale NiFe structures, reveal the same tendency. Switching time for such a process was obtained from calculations that show that subnanosecond switching times require combinations of large dc and rf magnetic fields.

Radiative Recombination of Spatially Extended Excitons in (ZnSe/CdS)/CdS Heterostructured Nanorods

We report on organometallic synthesis of luminescent (ZnSe/CdS)/CdS semiconductor heterostructured nanorods (hetero-NRs) that produce an efficient spatial separation of carriers along the main axis of the structure (type II carrier localization). Nanorods were fabricated using a seeded-type approach by nucleating the growth of 20-100 nm CdS extensions at [000 +/- 1] facets of wurtzite ZnSe/CdS core/shell nanocrystals. The difference in growth rates of CdS in each of the two directions ensures that the position of ZnSe/CdS seeds in the final structure is offset from the center of hetero-NRs, resulting in a spatially asymmetric distribution of carrier wave functions along the heterostructure. Present work demonstrates a number of unique properties of (ZnSe/CdS)/CdS hetero-NRs, including enhanced magnitude of quantum confined Stark effect and subnanosecond switching of absorption energies that can find practical applications in electroabsorption switches and ultrasensitive charge detectors.

SOA gate array recirculating buffer with fiber delay loop

We present a compact variable delay buffer for storage of 40 byte packets. The recirculating buffer is based on an InP SOA gate array two-by-two switch which provides greater than 40 dB of extinction, sub-nanosecond switching, and fiber-to-fiber gain. The switch is used with a fiber delay loop 450 centimeters, or 23 ns, in length. The buffer is demonstrated with greater than 98% packet recovery at 40 Gb/s for up to 184 ns of storage.

Subnanosecond switching of local spin-exchange coupled to ferromagnets

The dynamics of a single spin that is embedded in a tunnel junction between ferromagnetic contacts is strongly affected by the exchange coupling to the tunneling electrons. By using time-dependent equations of motion for the spin, which is under the influence of a spin-polarized tunneling current, it is shown that the magnetic field induced by bias voltage pulses allows for a subnanosecond switching of the local spin and the possibility of spin reversal is illustrated. Furthermore, it is shown that the time evolution of the Larmor frequency sharply peaks around the spin-flip event and it is argued that this feature can be used as an indicator for the spin flip.