Low-voltage Excitation Research Articles

Dielectric response of piezoelectric ceramics at low voltage excitations

An improved model is proposed for the interpretation of the dielectric response of a piezoelectric lead zirconate titanate (PZT) ceramic at low voltage excitations appropriate for microdevices by considering multiple relaxation processes. The model parameters are optimised in order to achieve a satisfactory agreement between the predicted values and experimental data obtained from room temperature measurements on a commercially available PZT-805 ceramic sample.

Ultrasonic Transmission-Mode Tomography Imaging for Liquid/Gas Two-Phase Flow

This paper details the development of noninvasive ultrasonic tomography for imaging liquid and gas flow. The transmission-mode approach has been used for sensing the liquid/gas two-phase flow, which is a kind of strongly inhomogeneous medium. Sixteen pairs of ultrasonic sensors have been used. By using low excitation voltage of 20 V, fan-shaped beam ultrasonic transmitters will emit ultrasonic pulses to the receivers. The investigations were based on the transmission and the reception of ultrasonic sensors that were mounted circularly on the surface of the experimental vessel. The algorithms used to reconstruct the concentration profile for two-phase flow using a fan-shaped beam scanning geometry were presented. By using a hybrid-binary reconstruction algorithm, real-time ultrasonic transmission-mode tomography has been developed. Experiments show that performance is acceptable with an image-reconstruction speed of 10 frames/s. The results of the experiments and possible future improvements were also discussed

A thin cover glass chip for contactless conductivity detection in microchip capillary electrophoresis

A microfabricated thin glass chip for contactless conductivity detection in chip capillary electrophoresis is presented in this contribution. Injection and separation channels were photolithographed and chemically etched on the surface of substrate glass, which was bonded with a thin cover glass (100 μm) to construct a new microchip. The chip was placed over an independent contactless electrode plate. Owing to the thinness between channel and electrodes, comparatively low excitation voltage (20–110 V in V p–p) and frequency (40–65 kHz) were suitable, and favorable signal could be obtained. This microchip capillary electrophoresis device was used in separation and detection of inorganic ions, amino acids and alkaloids in amoorcorn tree bark and golden thread in different buffer solutions. The detection limit of potassium ion was down to 10 μmol/L. The advantages of this microchip system exist in the relative independence between the microchip and the detection electrodes. It is convenient to the replacement of chip and other operations. Detection in different position of the channel would also be available.

Non-invasive imaging of liquid/gas flow using ultrasonic transmission-mode tomography

This paper details the development of non-invasive ultrasonic tomography for imaging liquid and gas flow. Transmission-mode approach has been used for sensing the liquid/gas two-phase flow, which is a kind of strongly inhomogeneous medium. A 16-pair of ultrasonic sensors have been used. By using low excitation voltage of 20V, fan-shape beam ultrasonic transmitters will emit ultrasonic pulses to the receivers. The investigations were based on the transmission and the reception of ultrasonic sensors that were mounted circularly on the surface of experimental vessel. The algorithms used to reconstruct the concentration profile for two-phase flow using fan-shape beam scanning geometry were presented. By using Hybrid-Binary Reconstruction algorithm (HBR), a real-time of ultrasonic transmission-mode tomography had been developed. Experiments showed that the performance is acceptable with the image reconstruction speed of ten frames per second. The results of the experiments and possible future improvements were also discussed.

2D ultrasonic arrays with low-voltage operation for high density electronics

The use of ultrasonic array transducers for NDT is growing rapidly, as commercial array controllers become more widely available. However, conventional 1D array designs limit the flexibility of such systems, for example, making it impossible to skew the beam on curved surfaces. As 2D arrays allow 3D beam steering, they are thus of major interest. However, the use of conventional excitation voltages, typically 200 V, with the many elements in 2D arrays may be inconvenient, making investigation of low-voltage operation worthwhile. The work reported here relates to array design for low-voltage operation for NDT. A 1D array was first produced, operating at approximately 1.5 MHz. This was based on a piezocomposite plate made with PZT 5A ceramic and epoxy resin. The plate was bonded to a PCB whose copper tracks defined the array elements, 10 mm long, 0.28 mm wide, and with edge-to-edge separation of 0.4 mm. The device was excited with a standard logic voltage of 3.3 V on a 75 mm-thick aluminium block. The pulse-echo insertion loss, using a signal reflected from the back wall of the aluminium, was found to be 59 dB. A 2D ultrasonic array has also been produced, with 16 elements in a 4 x 4 matrix, using the same piezocomposite material. In this case, the element size is 1.2 mm x 1.2 mm, and the edge-to-edge separation is 0.4 mm. In tests with 3.3 V peak-to-peak excitation voltage, the insertion loss was found to be 73 dB. The results suggest that arrays made with monolithic piezocomposite material have better performance for NDT than previous arrays made with monolithic ceramic and that low-voltage excitation will be viable in practice, with low noise amplification and appropriate signal processing.

Impedance of Goat Lens as a Function of Frequency at DC Voltages 0, 50, 100, 200 mV

Impedance characteristics of lens tissue has been studied using the AC impedance system (EG&G PARC, model 318) at different low voltage excitations using a Cole-Cole Plot. The extracellular resistance (Re), intracellular resistance (Ri), depressed angle (θ), total impedance (IZI), and phase angle (ϕ) of the tissue were measured. The impedance locus between the real part (Z′) and imaginary part (Z″) of the complex impedance of lens was examined at discrete frequencies ranging from 10 mHz to 10 Hz. A decrease in extra-cellular resistance (Re) and increase in distribution of the factor (α) of 56.8 KΩ, 48.1 KΩ, 32.8 KΩ, 13.4 KΩ, and 0.40, 0.43, 0.46, 0.53 were found at 0 mV, 50 mV, 100 mV, and 200 mV, respectively. The total impedance (| Z|) and phase angle (ϕ) were also evaluated and the observed frequency dependent for the frequency range was tested as a function of excitation voltage. An attempt has been made to explain the effect of voltage stress on lens impedance.

Investigation of thermally stimulated luminescence of zinc oxide with low-voltage excitation

This paper discusses the thermally stimulated luminescence and the brightness falloff of low-voltage cathodoluminescence in vacuum for ZnO:Zn and ZnO:Zn, Si. The intensity maxima of the thermally stimulated luminescence caused by gases adsorbed on the phosphor surface are observed at low accelerating voltages. It is shown that the adsorptivity of ZnO:Zn, Si is lower than that of ZnO:Zn, and this is the reason that the modified phosphor has a longer service life. A model of the action of a protective coating is considered. © 2005 Optical Society of America

Transient ion fluxes, driven by an external electric field in a thin electrolytic cell withblocking electrodes

A numerical algorithm is developed to examine the transient processes in an electrolyticcell with blocking electrodes when an external electric field is switched on and switched offstepwise in time. The algorithm is applicable for arbitrary mobilities and valence numbersof the ions and for large electric potentials, but is limited at present to small cell thickness,up to about 20 D lengths. The ion charge fluxes and the displacement currentcontributing to the total current in the cell have been evaluated and analysed. The ioncharge behaviour in the linear approximation regime (low excitation voltage) andnonlinear regime (high voltage) have been compared. The dependences of thepolarization and diffusion relaxation times on the ion parameters (valence andmobility), on the cell length and on the external electric potential are studied.

Effect of La and Zn addition on Y 2O 3:Eu phosphors

(Y 1− x La x ) 2O 3:Eu,Zn phosphors have been prepared by a citric acid gel method to develop a red-emitting phosphor with high luminance and good chromaticity under a low excitation voltage. The dependence of structural and luminescent properties on the composition ratio of La/Y and on the Zn addition was investigated. The La addition of x = 0.1 improves structural, cathode luminescence (CL) luminance, CL efficiency and chromaticity for the (Y 1− x La x ) 2O 3:Eu phosphors. Though the Zn doping has a tendency of further improvement in structure, CL luminance, CL efficiency and chromaticity, the Y 2O 3:Eu,Zn phosphor without La addition shows the best characteristic.

New electro-active paper actuator using conducting polypyrrole: actuation behaviour in LiClO 4 acetonitrile solution

The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5 mA/cm 2 current density or 0.7 V applied potential, respectively. The two types of actuators were constructed, namely: (1) Ppy/cellophane bi-layer; (2) Ppy/cellophane paper/Ppy tri-layer. These actuators showed a reversible and reproducible displacement in acetonitrile solution containing LiClO 4 (1 M). The maximum displacement of 9.1 mm was recorded for tri-layer device and 3.5 mm for bi-layer device in 1 M LiClO 4 acetonitrile solutions. The results obtained in acetonitrile solution containing 1 M LiClO 4 shows that the actuator requires very low excitation voltage of 0.2 MV m −1. The mechanism for this paper actuation phenomenon is addressed in this paper.

Evidence for Crossed Andreev Reflection in Superconductor-Ferromagnet Hybrid Structures

We have measured the nonlocal resistance of aluminum-iron spin-valve structures fabricated by e-beam lithography and shadow evaporation. The sample geometry consists of an aluminum bar with two or more ferromagnetic wires forming point contacts to the aluminum at varying distances from each other. In the normal state of aluminum, we observe a spin-valve signal which allows us to control the relative orientation of the magnetizations of the ferromagnetic contacts. In the superconducting state, at low temperatures and excitation voltages well below the gap, we observe a spin-dependent nonlocal resistance which decays on a smaller length scale than the normal-state spin-valve signal. The sign, magnitude, and decay length of this signal are consistent with predictions made for crossed Andreev reflection.

Low-Voltage Cathodoluminescence Properties of the Y 2 O 2 S : Eu Red Light Emitting Phosphor Screen in Field-Emission Environments

phosphors doped with different concentrations of Eu were fabricated by a high-temperature flux fusion method. For applications in field emission displays, phosphor powders were electrophoretically deposited on an indium-tin oxide coated glass substrate to form a phosphor screen. Cathodoluminescence properties of phosphor screens were examined at a low excitation voltage of 5 kV in a high-vacuum chamber and characteristics of phosphors, including brightness and wavelength data, are presented and discussed. The red emission brightness for the phosphor screens can be significantly improved by adjustment of the Eu additions, which decrease the coordinate slightly, while having no significant influence on the color performance. Considering the effects of Eu concentrations on red light emission spectra and brightness for phosphor screens, it is found that brightness for phosphor screens could be obtained up to with chromaticity of and and the Eu dopant concentration is suggested to be in the range 6-7.5 wt %. © 2002 The Electrochemical Society. All rights reserved.

Electro-active paperactuators

In this paper, the actuation mechanism ofelectro-active paper (EAPap) actuators is addressed and thepotential of the actuators is demonstrated. EAPap is a paperthat produces large displacement with small force under an electrical excitation. EAPap is made with a chemically treatedpaper by constructing thin electrodes on both sides of thepaper. When electrical voltage is applied on the electrodes theEAPap produces bending displacement. However, the displacementoutput has been unstable and degraded with timescale. Toimprove the bending performance of EAPap, different paperfibers - softwood, hardwood, bacteria cellulose, cellophane, carbon mixture paper, electrolyte containing paper and Koreantraditional paper, in conjunction with additive chemicals, weretested. Two attempts were made to construct the electrodes: thedirect use of aluminum foil and the gold sputtering technique.It was found that a cellophane paper exhibits a remarkablebending performance. When 2 MV m-1 excitation voltage wasapplied to the paper actuator, more than 3 mm tipdisplacement was observed from the 30 mm long paper beam.This is quite a low excitation voltage compared with that of otherEAPs. Details of the experiments and results are addressed.

Microelectromechanical system microbridge deflection monitoring using integrated spin valve sensors and micromagnets

Spin valve sensors are used to measure on chip, the deflection of microelectromechanical system resonators (bridges or cantilevers), with nm resolution. A spin valve sensor (10×2 μm2, MR=6.5%) was placed 3.2 μm away and 2.8 μm below the central region of an a-Si:H bridge, with a 1.2 μm air gap. The bridge movement was controlled by an applied voltage on the gate. In the undeflected state, a Co78Pt22 micromagnet (0.2 μm×18 μm×15 μm, Mrt=12.5 memu/cm2) deposited on top of the bridge, and saturated in an external field, creates a fringe field in the sensor shifting the transfer curve. An external bias field was then used to linearize the sensor response. Final sensor output versus bridge gate voltage was obtained using a low frequency square-wave gate excitation voltage (1 Hz). Bridge deflections from a few nm to 0.23 μm were detected.

Combined effect of electrode gap and radio frequency on power deposition and film growth kinetics in SiH4/H2 discharges

The combined effect of the variation of the interelectrode gap (1.3–2.5 cm) and radio frequency (13.56–50 MHz) on the properties of highly diluted silane in hydrogen discharges used for the deposition of microcrystalline silicon thin films is presented. The investigation included electrical and optical discharge measurements as well as the in situ determination of the film growth rate. In the lower frequencies regime, the increase of the interelectrode gap for the same applied voltage results in higher current flows and higher total power dissipation. On the other hand, at 50 MHz the variation of the interelectrode space has only a slight effect on the total power dissipation, due to the low excitation voltage. However, at all frequencies, the increase of the interelectrode space results in a drop of the power dissipation per discharge volume. This is related to the less effective energy transfer to the electrons that is due to the enhancement of the bulk relative to the sheath ohmic heating. The variation of the relative importance of the electron heating modes is reflected in the discharge radical production efficiency and the film growth rate.

Cooling of electrons in a silicon inversion layer.

Low temperature cooling of two-dimensional electrons in silicon-metal-oxide semiconductor field effect transistors is studied experimentally and found to be more effective than expected from the bulk electron-phonon coupling in silicon. The extracted heat transfer rate to phonons depends cubically on electron temperature, suggesting that piezoelectric coupling, which is absent in bulk silicon, dominates over deformation potential. As a result, at 100 mK, electrons farther than approximately 100 microm from the contacts are mostly cooled by phonons. Using long devices and low excitation voltage we measure electron resistivity down to approximately 100 mK and find that some of the "metallic" curves turn insulating below approximately 300 mK.

Optimization of Gd2 O 3-Based Red Phosphors Using Combinatorial Chemistry Method

Combinatorial chemistry was applied to the optimization of phosphors for displays. The phosphor is a promising candidate for red field emission display (FED) phosphors. Screening was performed in terms of cathodoluminescence at a low voltage excitation and photoluminescence. We developed a ternary material library of a triangle-type composition array to obtain the optimum composition of co-dopants. Three co-dopants (Al, Ca, Mg) were introduced into was a good host material for red FED phosphors at a low voltage excitation, and the cathodoluminescent efficiency of Al co-doped phosphor, was superior to that of the commercial red phosphor We also investigated the energy transfer between ions by analyzing the decay curves of emissions originating from energy states in terms of multipolar interactions. We can explain the quenching of emissions from in terms of a newly proposed cross relaxation in association with an intercenter diffusion. © 2002 The Electrochemical Society. All rights reserved.

Structure and Luminescence Properties of the ZnS:Cu, Al Phosphor for Low Voltage Excitation

The ZnS:Cu, Al phosphor has been studied for low voltage excitation field emission devices. To improve the cathodoluminescence (CL) brightness, the phosphor has been synthesized with iodide-type alkaline and alkali-earth metal as fluxes. CuI and were used as an activator and coactivator, respectively. The phosphor has been characterized in comparison with commercially available cathode ray tubes (CRTs) phosphor and conventionally prepared ones. Newly synthesized ZnS:Cu, Al phosphor prepared with iodide-type fluxes has shown higher CL brightness than commercially available phosphor and conventionally prepared ones. The phosphor structure has been analyzed using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. From the analysis, the phosphor particles were composed of cubic and hexagonal phases. The cubic phase was much more formed when iodide-type fluxes were used. This cubic phase helps the phosphor to have high brightness at low voltage operations. © 2001 The Electrochemical Society. All rights reserved.

Optical Characterization of Electrophoretically Deposited Phosphor

The optical performance of electrophoretically deposited phosphor (ZnS:Ag, P-22) was investigated. Densely packed and homogeneous deposits were made as a function of applied voltage and duration of deposition to give a range of deposit densities. These deposits showed a similar packing structure and cathodoluminescent efficiency. The electrophoretic process itself and conditions shown to enhance phosphor adhesion did not change the intrinsic efficiency of the phosphor under a low excitation voltage of 1-4 kV, applicable to field emission displays. © 2001 The Electrochemical Society. All rights reserved.

Synthesis and modification of red oxide phosphors for low voltage excitation

New red oxide phosphors Y2O3:Eu3+,Si4+ and (Y,Gd)2O3:Eu3+,Si4+,Bi3+ are synthesized by a coprecipitation method. Relative cathodoluminescence (CL) brightness at low voltages (⩽1 kV) is analyzed. At the low voltage excitation, luminance of the synthesized phosphors is higher than that of other commercially available red phosphors Y2O2S:Eu3+ and Y2O3:Eu3+. In particular, the difference of relative brightness between the commercially available phosphors and the synthesized Y2O3:Eu3+,Si4+ is larger at low voltages (⩽500 V) than at higher voltages. The synthesized (Y,Gd)2O3:Eu3+,Si4+,Bi3+ phosphor gives the same level of brightness as that of Y2O3:Eu3+,Si4+ at voltages greater than 500 V. (Y,Gd)2O3:Eu3+,Si4+,Bi3+ is coated with a conductive material SnO2:Eu3+. The coating of SnO2:Eu3+ shows a considerable improvement in brightness without a color shift. The excellent luminescence characteristics of (Y,Gd)2O3:Eu3+,Si4+,Bi3+ coated with SnO2:Eu3+, studied using field emitter arrays, suggests that our synthesized phosphor is practically applicable to field emission display devices.