High efficiency on-chip charge pump DC–DC converter for LCD drivers

An on-chip charge pump (CP) DC–DC converter applicable to potable displays is described. A merged 2×/3× booster eligible for both single-phase pumping and dual-phase pumping is developed. A closed-loop sensing scheme with analog/digital mixed-mode voltage regulation helps to ensure a low ripple output voltage and high power transfer efficiency. A test vehicle was implemented for a DC input range of 2.2–3.6 V and the DC output of 5 V with a load condition of 20 mA in a standard 0.35-μm 2poly-4metal CMOS process. The test results reveal output ripple of less than 80 mV and efficiency of 77.4% in the 2× dual phase mode.     

An analytical method for DC negative corona discharge in a wire-cylinder device at high temperatures

This paper proposes an analytical solution for DC negative corona discharge in a wire-cylinder device based on experimental results in which both the corona and drift regions are considered; this approach aims to provide a theoretical method for analyzing electrostatic precipitation at high temperatures. The inter-electrode space is divided into three zones, namely, the ionization layer, the attachment layer (corona region) and the drift region, to investigate the space charge concentration and the electric field distribution. The boundary of the ionization layer is assumed to be the radius at which the rate of ionization balances that of electron attachment. The radius where the value of E/N equals 110 Td is recommended as the boundary of the attachment layer. It was determined that an increasing temperature leads to a decrease in the largest space charge number density and the largest electric field in the drift region that can be provided by a discharging device. With respect to the device in the present work, when the temperature increases from 350 °C to 850 °C, the largest electric field decreases from ∼9 × 10⁶ V/m to ∼3 × 10⁶ V/m, and the largest charge number density decreases from ∼1.3 × 10¹⁵ m⁻³ to 6.4 × 10¹⁴ m⁻³. The radius of the corona region, the space charge number density and the electric field increase as the applied voltage increases at a given temperature. For example, at a temperature of 550 °C, when the applied voltage increases from 10,500 V to 18,879 V, the radius of the corona region increases from ∼2.9 mm to ∼4.9 mm. It appears to be unreasonable to use a constant value that is calculated from Peek's formula as the electric field at the surface of the cathode under all of the conditions.     

Analysis of electrical characteristics of Er/p-InP Schottky diode at high temperature range

We report on the temperature-dependent electrical characteristics of Er/p-InP Schottky barrier diodes. The current–voltage (I–V) and capacitance–voltage (C–V) measurements have been carried out in the temperature range of 300–400 K. Using thermionic emission (TE) theory, the zero-bias barrier height (Φ_bo) and ideality factor (n) are estimated from I–V characteristics. It is observed that there is a decrease in n and an increase in the Φ_bo with an increase in temperature. The barrier height inhomogenity at the metal/semiconductor (MS) interface resulted in Gaussian distribution of Φ_bo and n. The laterally homogeneous Schottky barrier height value of approximately 1.008 eV for the Er/p-InP Schottky barrier diodes is extracted from the linear relationship between the experimental zero-bias barrier heights and ideality factors. The series resistance (R_s) is calculated by Chenug's method and it is found that it increases with the decrease in temperature. The reverse-bias leakage current mechanism of Er/p-InP Schottky diode is investigated. Both Poole–Frenkel and Schottky emissions are described and discussed. Furthermore, capacitance–voltage (C–V) measurements of the Er/p-InP Schottky contacts are also carried out at room temperature in dark at different frequencies of 10, 100 and 1000 kHz. Using Terman's method, the interface state density is calculated for Er/p-InP Schottky diode at different temperatures.     

Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

PLD and RF-PLD synthesis of Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript> ferroelectric thin films for electrically controlled devices

Ba_0.6Sr_0.4TiO₃ (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition (PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with size of spherical grains up to 150 nm. The capacitance–voltage (C–V) characteristics of the BST films were performed by applying a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been measured at room temperature.     

A fiber-optic voltage sensor based on macrobending structure

We propose and demonstrate an optical voltage sensing scheme based on a macrobending optical fiber in a ratiometric power measurement system. This novel approach to sensing has not been utilized before and has the advantage that the sensor involves simple fabrication compared to existing fiber-optic voltage sensors. To prove the feasibility of such a fiber-optic sensor, a sensor for a voltage range from 0∼100 V is demonstrated, with a resolution of 0.5 V. The sensor is robust, linear, and shows a competitive measurement resolution. The sensor can be easily scaled to suit other voltage levels and be effectively combined with optical current sensors.     

Numerical and experimental studies of collection efficiency of an ion electrostatic collector for a mini-volume electrical PM detector

The experimental efficiency was numerically and experimentally studied for collecting negative and positive ions in a coaxial cylindrical electrostatic collector for a mini-volume electrical PM detector. The commercial computational fluid dynamics software package COMSOL Multiphysics™ was used to predict the behaviors of the flow and electric fields as well as the particle trajectories in the collecting zone of the ion collector. In the experiment, the ions were generated by a corona-needle ionizer with concentrations greater than 10¹³ ions/m³, the positively and negatively applied voltages at the inner electrode ranged from 0 to 45 V and the ion flow rates ranged from 1 to 5 L/min. For these ion flow rates, 1–5 L/min, the ion precipitates due to space charge and diffusion effects ranged from 92 to 97 % for positive ions and 91–97 % for negative ions. The total collection efficiency of the collector increased to 100% at collection voltages larger than 5, 20 and 40 V respectively for the ion flow rates of 1, 3 and 5 L/min for both positive and negative ions. Numerical calculation results of the ion trajectory in the collecting zone of the collector; showed good agreement with the experimental results of the total collection efficiency and can be used to support the bettering of designing in order to refine an ion collector after the charger or ionizer in a mini-volume electrical aerosol detector. Finally, this shows that this ion collector was proven to be particularly useful as an electrostatic collector for positive and negative ions after the charger or ionizer in a mini-volume electrical aerosol detector.     

Temperature dependent electrophysical characteristics of GaAs-polymer composite varistors

A composition of GaAs-polymer tiny particles was pressed at a temperature of 130 °C and a pressure of 60 MPa and its current–voltage characteristic was studied. The result shows that the prepared disk has varistor behavior and can therefore be used to protect circuits from low overvoltage transients higher than 62 V. Temperature dependence of current-voltage characteristic and the electrical conductivity of the sample were investigated in the temperature range of 25–100 °C. It has been found that increase in temperature results in lower breakdown voltage and nonlinearity coefficient. At high temperatures, nonlinearity in the I–V characteristic of sample disappears and the conductivity becomes Ohmic in nature. The sample has hysteresis which decreases through increase in temperature. Annealing effect on leakage current and breakdown voltage was both investigated and analyzed using SEM micrographs. Finally, the electrical bandgap of the sample was measured.     

Electrophoresis and orientation of multiple wall carbon nanotubes in polymer solution

This paper contains an in-depth analysis of the electrophoresis of multi-wall carbon nanotubes (MWNTs) in liquid epoxy where electrophoresis experiments under DC and AC fields were carried out for five different types of multi-wall carbon nanotubes (MWNTs). DC electrophoresis and particle image velocimetry were used to determine the electrophoretic particle mobility and zeta potential, where the MWNTs with the largest outer diameter and length led to the highest mobility values. The orientation and agglomeration of MWNTs into “striation” lines under AC electrophoresis were investigated by analysing the hue, saturation and intensity of the transmitted polarised light under microscope, following a schedule of step-wise applied voltage in the range of 0 to 100 V. Plots of hue and saturation as a function of the applied voltage were used to assess the degree of orientation and density of orientated MWNT structures, respectively, and to determine an optimum AC electric field value for the orientation of a specific MWNT type by electrophoresis.     

Current analysis of DC negative corona discharge in a wire-cylinder configuration at high ambient temperatures

To study the characteristics of DC negative corona discharge in a wire-cylinder configuration at an ambient temperature range of 350–850 °C, the I–V characteristics and the current composition are analyzed under different conditions. A simple method is proposed to determine the DC corona onset threshold voltage. At high ambient temperatures, in the DC negative corona discharge gap, some electrons are not attached to the electronegative gas molecules and move to the anode tube. Thus, these electrons form an electron current, which may account for most of the total discharging current. The ratio of the electron current to the total discharging current increases with increasing temperature. In a mixture of O₂ and N₂ and a mixture of CO₂ and N₂, the ratio of electron current increases with increasing N₂ content in the mixtures. The cathode material has little influence on the corona discharge characteristics at high ambient temperatures.     

Optimization of un-tethered, low voltage, 20-100kHz flexural transducers for biomedical ultrasonics applications

This paper describes optimization of un-tethered, low voltage, 20-100 kHz flexural transducers for biomedical ultrasonics applications. The goal of this work was to design a fully wearable, low weight (<100 g), battery operated, piezoelectric ultrasound applicator providing maximum output pressure amplitude at the minimum excitation voltage.Such implementation of ultrasound applicators that can operate at the excitation voltages on the order of only 10-25 V is needed in view of the emerging evidence that spatial-peak temporal-peak ultrasound intensity (I_SPTP) on the order of 100 mW/cm² delivered at frequencies below 100 kHz can have beneficial therapeutic effects. The beneficial therapeutic applications include wound management of chronic ulcers and non-invasive transdermal delivery of insulin and liposome encapsulated drugs.The early prototypes of the 20 and 100 kHz applicators were optimized using the maximum electrical power transfer theorem, which required a punctilious analysis of the complex impedance of the piezoelectric disks mounted in appropriately shaped metal housings.In the implementation tested, the optimized ultrasound transducer applicators were driven by portable, customized electronics, which controlled the excitation voltage amplitude and facilitated operation in continuous wave (CW) or pulsed mode with adjustable (10-90%) duty cycle. The driver unit was powered by remotely located rechargeable lithium (Li) polymer batteries. This was done to further minimize the weight of the applicator unit making it wearable. With DC voltage of approximately 15 V the prototypes were capable of delivering pressure amplitudes of about 55 kPa or 100 mW/cm² (I_SPTP). This level of acoustic output was chosen as it is considered safe and side effects free, even at prolonged exposure.     

Improved InGaP/GaAs/InGaP δ-doped double-HBT with InGaP passivation layer and effects of layer-thickness on device performance

This paper reports on the fabrication and characterization of InGaP/GaAs/InGaP δ-doped double heterojunction bipolar transistors (δ-DHBTs) with an InGaP passivation layer. Effects of passivation layer thickness on the performance of the studied devices were investigated. Various passivation layer thicknesses (1000Å to 0Å at a rate of −200Å) were employed in the device fabrication. Experimental findings show that both collector current and current gain are enhanced at fixed base currents when a 400 ∼  600-Å thick InGaP passivation layer is used. We obtained current gains of 350 and 280 at a base current of 100 μÅ for δ-DHBTs with a 400-Å thick InGaP passivation layer and without one, respectively. Furthermore, all devices exhibit a collector current saturation voltage (knee voltage) of less than 2.5 V. A control DHBT without a doping spike at the B–C heterointerface has a knee voltage of 3.5 V. At the same time, its current gains as a function of collector current are strongly dependent on the B–C reverse voltage. These high current gains with small knee voltages obtained in improved δ-DHBTs suggested that both the E–B and the B–C potential spikes are eliminated by δ-doped spikes.     

Fabrication and characteristics of photodiode based on ZnO nanowire arrays and spray-coated regioregular P3HT layers

A photodiode based on well-aligned ZnO nanowire arrays (ZNAs) and spray-coated regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) layers hybrid hetero junctions was fabricated, and its electrical characteristics in dark and under illumination with a solar simulator were investigated. Current–voltage (I–V) data of ITO/ZNAs/P3HT/Ag device in dark and under illumination showed typical diode characteristics. A rectification ratio (RR) of 22.7 at 1.7 V and a low turn-on voltage of 0.4 V in dark were obtained. Also, the photodiode with high photo-response in the order of 0.31 A/W at -2 V using 80 mW/cm² illumination power was observed. Upon increasing illumination power from 40 to 100 mW/cm², the RR value for the photodiode continuously was improved with a highest value of 12.5.     

Tribocharging in a rotating shaft–oil–lip seal system for different engine base oils,additive, and their blends

The paper presents the results of experiments on tribocharging of different mineral, semisynthetic, and synthetic base oils and their blends with additives. An antiwear additive ZDDP (zinc dialkyldithiophosphate) is tested when added to base oils in different percentages by weight. Experiments are carried out on the specially built experimental facility to be a simplified model of an engine crankcase in whose interior an earthed metal shaft rotates at given angular velocities. The potential of a stiffening ring of a lip seal is measured directly with an electrometer. The potential is a measure of tribocharging in a rotating shaft–oil–lip seal system, friction junction, and especially between both interfaces: shaft surface–oil and oil–lip of a lip seal. The experimental results are presented in the form of some characteristics that are relationships of the potential induced in the stiffening ring with oil's temperature for different angular shaft's velocities and additives, contents. The oil's temperature ranges from 60 to 110 °C and is controlled automatically. The angular velocities of a shaft used are 500 and 1500 rpm. The additive contents in the blends with different base oils are 0.1 and 0.2%. The pure base oils of all the types and some lip seals are also examined. Moreover, the influence of an external DC electric field applied between the earthed shaft and the stiffening ring on the braking torque of the shaft is examined for a range of temperatures of the pure oils and their blends with the additive used, angular velocities, and additive contents. The electric field is produced while applying the high DC voltage of both polarities between the shaft and the ring. The absolute value of the voltage is in a range from 500 to 1500 V.     

Electric field induced metal–insulator transition in VO2 thin film based on FTO/VO2/FTO structure

A VO₂ thin film has been prepared using a DC magnetron sputtering method and annealing on an F-doped SnO₂ (FTO) conductive glass substrate. The FTO/VO₂/FTO structure was fabricated using photolithography and a chemical etching process. The temperature dependence of the I–V hysteresis loop for the FTO/VO₂/FTO structure has been analyzed. The threshold voltage decreases with increasing temperature, with a value of 9.2 V at 20 °C. The maximum transmission modulation value of the FTO/VO₂/FTO structure is 31.4% under various temperatures and voltages. Optical modulation can be realized in the structure by applying an electric field.     

Simultaneous removal of nitrogen oxides and diesel soot particulate in nano-structured electrochemical reactor

Simultaneous decomposition of nitrogen oxides (NO_x) and solid state graphite particles were carried out using a 8 mol% Y₂O₃ doped ZrO₂ (YSZ) based electrochemical reactor with a nano-structured NO_x selective multilayer cathode and an oxidative porous anode. The ceramic electrochemical cell was prepared by screen-printing a Pt and a NiO–YSZ pastes as cathode layers and a 12 CaO7Al₂O₃–Pt paste as an anode layer on the YSZ electrolyte, respectively. Simultaneous decomposition of NO_x and graphite particles was investigated using the cell with coated graphite particles on the surface of the 12 CaO7Al₂O₃–Pt composite anode in 1000 ppm NO_x–He gas flow under applying DC voltage at 475 °C. The coated graphite particles at the anode were removed completely with 80% NO_x decomposition by electrochemical reactions.     

Highly stable hafnium–tin–zinc oxide thin film transistors with stacked bilayer active layers

Hf–Sn–Zn–O (HTZO) thin films were prepared on SiO₂/SiN_x substrates at room temperature by the direct current (DC) magnetron sputtering of Hf-doped Sn–Zn–O targets. The characteristics of films with different amounts of Hf were analyzed. Amorphous HTZO films were obtained by increasing the Hf content, while polycrystalline films have not shown with Hf doping. With the proper Hf concentration in the HTZO films (∼2.0 atomic % Hf/(Hf + Sn + Zn + O)), HTZO films demonstrated good performance as an oxide semiconductor channel material in thin film transistors (TFTs) with a field effect mobility (μ_FE) of 10.9 cm²V⁻¹ s⁻¹, an on/off current ratio of 10⁹, and a subthreshold voltage swing of 0.71 V/decade.     

Transparent CdO/n-GaN(0001) heterojunction for optoelectronic applications

Undoped CdO films were prepared by sol–gel method. Transparent heterojunction diodes were fabricated by depositing n-type CdO films on the n-type GaN (0001) substrate. Current–voltage (I–V) measurements of the device were evaluated, and the results indicated a non-ideal rectifying characteristic with I_F/I_R value as high as 1.17×10³ at 2 V, low leakage current of 4.88×10⁻⁶ A and a turn-on voltage of about 0.7 V. From the optical data, the optical band gaps for the CdO film and GaN were calculated to be 2.30 eV and 3.309 eV, respectively. It is evaluated that interband transition in the film is provided by the direct allowed transition. The n-GaN (0001)/CdO heterojunction device has an optical transmission of 50–70% from 500 nm to 800 nm wavelength range.     

Substrate bias effects during diamond like carbon film deposition by microwave ECR plasma CVD

Diamond like carbon (DLC) coatings were deposited on silicon(1 1 1) substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using a plasma of Ar and CH₄ gases under the influence of DC self bias generated on the substrates by application of RF (13.56 MHz) power. DLC coatings were deposited under the varying influence of DC bias (−60 V to −150 V) on the Si substrates. Deposited films were analyzed by different techniques like: X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), Hardness and elastic modulus determination technique, Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurement. The results indicate that the film grown at −100 V bias has optimised properties like high sp³/sp² ratio of carbon bonding, high refractive index (2.26–2.17) over wide spectral range 400–1200 nm, low roughness of 0.8 nm, high contact angle (80°) compared to the films deposited at other bias voltages (−60 V and −150 V). The results are consistent with each other and find august explanation under the subplantation model for DLC growth.     

Structure and electrical properties of HfO<Subscript>2</Subscript> high-<Emphasis Type="Italic">k</Emphasis> films prepared by pulsed laser deposition on Si (100)

High-k gate dielectric hafnium dioxide films were grown on Si (100) substrate by pulsed laser deposition at room temperature. The as-deposited films were amorphous and that were monoclinic and orthorhombic after annealed at 500°C in air and N₂ atmosphere, respectively. After annealed, the accumulation capacitance values increase rapidly and the flat-band voltage shifts from −1.34 V to 0.449 V due to the generation of negative charges via post-annealing. The dielectric constant is in the range of 8–40 depending on the microstructure. The I–V curve indicates that the films possess of a promising low leakage current density of 4.2×10⁻⁸ A/cm² at the applied voltage of −1.5 V.