Single Voltage Pulse Research Articles

PRIMARY ATOMIZATION AND DROP SIZE CHARACTERISTICS OF AN ELECTROSTATIC DIELECTRIC LIQUID PULSED ATOMIZER

Primary atomization and drop size characteristics are presented for a fuel injector which has been modified to electrically charge dielectrics such as hydrocarbon liquids used in the transport industry. Global spray characteristics are discussed for a conventional low-pressure fuel injector with no electrostatic assistance alongside the electrostatically modified version, where the latter may also be referred to as a "fully pulsed charge injection atomizer." The atomizer is a novel device that consists of sealed high-voltage components retrofitted onto an existing fuel injector as described in Kourmatzis and Shrimpton, Journal of Electrostatics, vol. 69, pp. 157−167 (2012). Experiments conducted with continuous pulsed frequencies ranging from 1−20 Hz at average injection velocities of approximately 10 m/s up to an applied voltage of 4 kV reveal that supplying a pulsed electric charge on a pulsed flow succesfully promotes primary atomization and dispersion. In addition to continuous pulsing, single voltage pulses have been applied to the fuel injector solenoid and high-voltage electrode, at pulse widths down to 5 ms. Localized jet breakup images have revealed the time taken for a small electrically charged dielectric liquid fuel packet to atomize into droplets over a range of voltages, and, as with previous work conducted for pulsed voltage steady flow systems, frequency has no measurable effect on the atomization characteristics of pulsed flow pulsed voltage systems. Particle digital image analysis was employed in order to determine the drop sizes produced by the electrostatically modified fuel injector, and, while atomization is poor at locations close to the breakup length, droplet sizes of half the orifice diameter may be achieved with only ~2 mW of electrical power.

Position dependent measurement of single event transient voltage pulse shapes under heavy ion irradiation

A CMOS inverter in 90 nm CMOS bulk technology was exposed to heavy ion radiation (Au-197) at a micro-beam facility. The targeted inverter occupies an area of 6×3 µm2. The resulting single event transient (SET) voltage pulses at the output were measured using an on-chip analogue sense amplifier. The output of the amplifier was recorded with a 15 GHz real-time oscilloscope. Depending on the location of the ion hits strongly different pulse shapes were observed.

Effect of Pulse Polarity on the Propagation of a Large-Volume Discharge in a Nonuniform Electric Field

The nanosecond single-pulse voltage was employed here to generate a large-volume discharge between the wire-plane electrodes in nitrogen. In order to find out the effect of pulse polarity on the propagation of a large-volume discharge, both the positive and negative pulses were applied to the wire-plane electrodes, respectively. Images presented here reveal that the discharge channels are more homogeneous under the negative pulse, and the propagation speed of the discharge channels is faster under the positive pulse.

Uniformity enhancement of incident dose on concave surface in plasma immersion ion implantation assisted by beam-line ion source

Plasma immersion ion implantation (PIII) is a promising surface treatment technique for the irregular-shaped components. However, it is difficult to achieve uniform implantation along the surface of a concave sample due to the propagation and overlapping effect of plasma sheath. In this paper, a new ion implantation process is presented for improving the dose uniformity, especially for enhancing the lateral dose of the samples with concavities. In PIII enhanced by beam-line ions process, a beam-line ion source with certain energy is introduced from an external source into the concavity to suppress the sheath propagation and consequently to improve the dose uniformity. The time-dependent evolution of the potential, electrical field and the particle movement surrounding the surface of concave sample is studied by a particle-in-cell/Monte Carlo collision (PIC/MCC) simulation during a single bias high voltage (HV) pulse. The simulation results show that the plasma sheath propagation surrounding the concave sample is suppressed effectively by beam-line ions, and can be quasi-steady state during a single HV pulse. The influence of the energy of induced beam-line ions on the incident ion dose and energy distribution is discussed. Compared with the traditional PIII process, the dose uniformity of the sample surface is improved obviously due to the increase of the ions implanted into the lateral surface.

Electrothermal behavior of the elements of SOS CMOS chips

Using two-dimensional (2D) numerical electrothermal simulation, the character of heating of SOS CMOS chip elements under the action of single voltage pulses was determined. The experiments carried out on SOS CMOS chips confirmed the validity of the developed numerical model of thin structure heating under the action of single voltage pulses. It was confirmed that the dependence of the pulse electric strength level on a single voltage pulses (SVP) length for SOS CMOS chips is weaker than that for CMOS chips fabricated using bulk or epitaxial technologies.

Self-heating of silicon microwires: Crystallization and thermoelectric effects

Abstract

Nano-patterning of through-film conductivity in anisotropic amorphous carbon induced using conductive atomic force microscopy

Direct nanometer patterning of through-film electrical conductivity on carbon films is crucial in the development of carbon materials for nanotechnology. Typically, nanometer topographical surface modification can be created using scanning probe microscopy techniques producing surface artifacts which do not extend through the film. Here, we demonstrate the direct nano-patterning of through-film conductivity on highly oriented anisotropic carbon films by applying single voltage pulses (6 V) to a conductive atomic force tip in contact with the film. The thus induced conductivity is at least four orders of magnitude higher than that of the nominal area.

Nonlinear behaviors in a pulsed dielectric barrier discharge at atmospheric pressure

In this paper, the temporal nonlinear behaviors of pulsed dielectric barrier discharge in atmospheric helium are studied numerically by a one-dimensional fluid model. The results show that the common single-period pulsed discharge with two current pulses per single voltage pulse can take place over a broad parameter range. The rising and falling times of the voltage pulse can affect the discharge characteristics greatly. When the discharge is ignited by a pulse voltage with long rising and falling times, a single-period pulsed discharge with multiple current peaks can be observed. Under appropriate rising and falling times of the voltage pulse, a stable period-two discharge can occur over wide frequency and voltage ranges. Also this period-two discharge can exhibit different current and voltage characteristics with changing the duty cycle. With other parameters fixed, the pulsed DBD could be driven to chaos through period-doubling route by increasing either the falling time or the frequency of voltage pulse.

Electric discharge control of flow separation on oblique airfoil

The possibility of controlling flow separation on an oblique airfoil using dielectric-barrier discharge has been experimentally studied. The experiments were performed at subsonic flow velocities in a broad range of the angle of attack. The results of measurements of the velocity and surface pressure fields and an analysis of the flow patterns show that the application of electric discharge allows the interval of the angles of attack for separation-free flow past the airfoil to be significantly increased. Various discharge regimes have been studied, including those with continuous activation by single voltage pulses with a frequency of 0.5–5 kHz and by pulse trains at a repetition rate of 1–100 Hz. The efficiency of the flow separation control has been studied as dependent on the electrical parameters, frequency characteristics, and position of the discharge relative to the flow separation line.

Electrostatic manipulation of a dielectric microparticle considering surface conductivity using a single probe

In this study, we have developed the technique of electrostatic manipulation of a dielectric microparticle by a single probe. The manipulation system consists of three objects: a conductive probe as a manipulating tool, a conductive plate as a substrate, and a dielectric particle that dubs as a microparticle. In manipulating 60 μm in diameter particles of polystyrene, when a constant probe-substrate voltage was applied, we observed the phenomenon of the particle repeatedly moving up and down between the substrate and the probe tip, similarly to a “micro-dribble.” In order to understand the mechanism of the phenomenon, we have proposed a model with a resistor-capacitor circuit in consideration of the surface conductivity of the dielectric particle such that the model can explain the micro-dribble phenomenon in terms of the time constant of the circuit. By a single-pulse voltage the duration of which was designed (selected) on the basis of the frequency of the observed micro-dribble, we experimentally demonstrated the electrostatic micromanipulation by picking up/placing the polystyrene particle using the single probe. Although the success rate of 42% requires further improvement, the experimental result indicates the feasibility of the technique, which can be applied to future technology for microdevice packaging or assembly.

Melting and crystallization of nanocrystalline silicon microwires through rapid self-heating

Nanocrystalline silicon microwires are self-heated through single, large amplitude, and microsecond voltage pulses. Scanning electron micrographs show very smooth wire surfaces after the voltage pulse compared to as-fabricated nanocrystalline texture. Voltage-pulse induced self-heating leads to significant conductance improvement, suggesting crystallization of the wires. The minimum resistivity during the pulse is extracted from wires of different dimensions as 75.0±4.6 μΩ cm, matching previously reported values for liquid silicon. Hence, nanocrystalline silicon microwires melt through self-heating during the voltage pulse and resolidify upon termination of the pulse, resulting in very smooth and less-resistive crystalline structures.

Numerical Simulation of Townsend Discharge, Paschen Breakdown and Dielectric Barrier Discharges

Practical understanding of electrical discharges between conductors or between conductors and dielectrics is instrumental for the development of novel charging devices for Digital Printing Applications. The work presented on this paper focuses on fundamental aspects related to the inception of electrical discharges and breakdown in the initial stages (few 100's of μs) to a detail hard to match with experimental techniques. Numerical simulations of 1-D Townsend and Dielectric Barrier Discharges (DBDs) are performed using a commercial Finite Element package (COMSOL). A combined fluid model for the electron and Ion fluxes is used together with a local field approximation on a 1-D domain comprised of Nitrogen gas. The renowned Paschen breakdown result is successfully predicted numerically. Results are shown for the transient Townsend discharge that leads to this breakdown offering insight into the positive feedback mechanism that enables it. These transient results show how impact ionization combined with cathode secondary emission generate increasing waves of positive ions that drift towards the cathode again self feeding the discharge process. The simulation is then extended to predict the nature of a DBD in the case of a single voltage pulse.

The effect of the shape of single, sub-ms voltage pulses on the rates of surfaceimmobilization and hybridization of DNA

Electric fields generated by single square and sinusoidal voltage pulses withamplitudes below 2 V were used to assist the covalent immobilization ofsingle-stranded, thiolated DNA probes, onto a chemically functionalizedSiO2 surface and to assist the specific hybridization of single-stranded DNA targets withimmobilized complementary probes. The single-stranded immobilized DNA probeswere either covalently immobilized (chemisorption) or electrostatically adsorbed(physisorption) to a chemically functionalized surface. Comparing the speed of electricfield assisted immobilization and hybridization with the corresponding controlreactions (without electric field), an increase of several orders of magnitude isobserved, with the reaction timescaled down from 1 to 2 h to a range between100 ns and 1 ms. The influence of the shape of the voltage pulse (square versussinusoidal) and its duration were studied for both immobilization and hybridizationreactions. The results show that pulsed electric fields are a useful tool to achievetemporal and spatial control of surface immobilization and hybridization reactions ofDNA.

Atomic Force Microscopy Study of a Voltage Effect on CdZnTe Crystal Dimensions

In this work we studied the influence of an external electric voltage on spatial dimensions of CdZnTe mixed crystals. In order to get an absolute magnitude of the sample thickness and to gain insight to the changes of lateral dimension, in quasi-bulk 3 μm thick CdZnTe layers grown by molecular beam epitaxy square craters were formed by ion sputtering in a secondary ion mass spectrometer. The vertical and lateral dimensions of the craters were studied by the atomic force microscopy. The atomic force microscopy measurement revealed that the thickness of the CdZnTe layer increases in a result of applying a single voltage pulse to the sample surface and decreases reversibly after applying reversely biased voltage. The voltage triggering was high enough to switch the conductivity state of the sample i.e., the effect of thickness change is accompanied by the effect of conductivity switching. The thickness change is significant, reaching several percents of the entire layer thickness.

Non-volatile ferroelectric control of ferromagnetism in (Ga,Mn)As

Multiferroic structures that provide coupled ferroelectric and ferromagnetic responses are of significant interest as they may be used in novel memory devices and spintronic logic elements. One approach towards this goal is the use of composites that couple ferromagnetic and ferroelectric layers through magnetostrictive and piezoelectric strain transmitted across the interfaces. However, mechanical clamping of the films to the substrate limits their response. Structures where the magnetic response is modulated directly by the electric field of the poled ferroelectric would eliminate this constraint and provide a qualitatively higher level of integration, combining the emerging field of multiferroics with conventional semiconductor microelectronics. Here, we report the realization of such a device using (Ga,Mn)As, which is an archetypical diluted magnetic semiconductor with well-understood carrier-mediated ferromagnetism, and a polymer ferroelectric gate. Polarization reversal of the gate by a single voltage pulse results in a persistent modulation of the Curie temperature of the ferromagnetic semiconductor. The non-volatile gating of (Ga,Mn)As has been made possible by applying a low-temperature copolymer deposition technique that is distinct from pre-existing technologies for ferroelectric gates on magnetic oxides. This accomplishment opens a way to nanometre-scale modulation of magnetic semiconductor properties with rewritable ferroelectric domain patterns, operating at modest voltages and subnanosecond times.

Voltage-pulse-induced electromigration

We propose and demonstrate a voltage-pulse-induced electromigration technique, inwhich electromigration in a gold nanowire is induced for a short period of about10 µs by applying a voltage pulse. A local temperature analysis and a controlled electromigrationexperiment in the presence of voltage pulses indicate successful control of thisvoltage-pulsed-induced electromigration. We also measured the current–voltagecharacteristics of the nanowire after the application of each single voltage pulse toinvestigate the stochastic behavior of electromigration. A pulse duration shorter than thethermal relaxation time of the nanowire would allow us to separately control the localtemperature and driving force for electromigration.

Dynamic photorefractivity guided by single-pulse voltage

The dynamic photorefractivity in a cell with photoconducting orienting layers, filled with a nematic liquid crystal (LC) 6CHBT and a mixture of anthraquinone dyes AD1 and AD2, has been investigated. The single-pulse mode, in which the polarity and amplitude of a dc electric field applied to an LC cell are switched for a fixed time interval, has been used. The scheme of dynamic self-diffraction of low-power laser beams was used in the experiment. The dependences of the width and intensity of diffraction pulses on the bias and switching voltages have been investigated. It is established that the width and intensity of the diffraction pulse arising after initial voltage recovery depends also on the switching pulse width. At the optimal width of the control pulse, the diffraction efficiency increases by two orders of magnitude.

Online and Offline Rotary Regression Analysis of Torque Estimator for Switched Reluctance Motor Drives

A new torque estimator for switched reluctance motor (SRM) drives based on 2-D rotary regression analysis is presented in this paper. The proposed torque estimator is composed of a bicubic regressive polynomial as a function of rotor position and input current. The regressive coefficients can be computed offline or online from the torque characteristics acquired either experimentally or from numerical computation. Furthermore, a torque estimation method by taking mutual coupling into consideration is proposed. It can be seen that the estimated and experimentally obtained self-coupling and mutual-coupling torque characteristics are in good agreement with each other. In addition, the dynamic torque waveforms with and without the mutual coupling, estimated by the proposed estimator, are found to be virtually the same as those obtained from the bicubic spline interpolation for SRM drives with single-pulse voltage, hysteresis current chopping, as well as with voltage pulse width modulation control. The success of all the case studies being reported is a good validation of the usefulness and accuracy of the proposed real-time torque estimator that, as described in this paper, can be used to quickly estimate the instantaneous output torque of SRM drives.

Estimation of Single Event Transient Voltage Pulses in VLSI Circuits From Heavy-Ion-Induced Transient Currents Measured in a Single MOSFET

Described is an estimation technique of single event transient voltage pulses in VLSI circuits from heavy-ion-induced transient currents measured in a single MOSFET. Waveforms of the transient voltage pulses are fully estimated by using transient current data obtained in various drain voltage conditions. Modeling of the irradiated device behavior for use in device/circuit simulations is not required. The concept is validated using a 2-D mixed-mode device simulation.

The non-destructive threshold of the graphite surface by STM in the ultra-fast pulse mode

In this paper single ultra-fast voltage pulses are introduced to the Pt/Ir tip of a scanning tunnelling microscope (STM), and the non-destructive threshold of the graphite surface is studied systematically in a wide range of pulse durations (from 104 to 8ns). Considering the waveform distortion of the pulses at the tunnelling region, this paper gives the corrected threshold curve of pulse amplitude depending on pulse duration. A new explanation of threshold power has been suggested and fits the experimental results well.