Current-voltage Slope Research Articles

Electrophysical characteristics of power MOSFETs additionally implanted with nitrogen ions

The electrical characteristics of power MOSFETs additionally implanted with nitrogen ions have been studied. Ion implantation of nitrogen was carried out through a protective oxide of 23 nm thickness with energies of 20 and 40 keV and doses of 1 ⋅ 1013‒5 ⋅ 1014 cm–2. Rapid thermal annealing was carried out at temperature of 900 or 1000 °C for 15 s. It has been established that nitridisation of the gate dielectric makes it possible to reduce the noise of the gate leakage currents and their dispersion. In the direct order of heat treatment (first rapid thermal annealing, and then the removal of the protective oxide), for samples prepared with an additional operation of nitrogen ion implantation, there is an increase in the threshold voltage compared to control samples. The capacitance of the gate dielectric in the case of implantation of nitrogen ions in the direct order of heat treatment is less than for control samples. It has been established that in the direct order of rapid thermal annealing, the doses of nitrogen ion implantation do not cause significant changes in the maximum value of the current-voltage slope. At the same time, in all studied cases, there is a shift in the maximum value of the current-voltage slope towards higher gate voltages. In the reverse order of heat treatment (first the removal of the protective oxide, and then rapid thermal annealing), there are no significant differences in the value of the threshold voltage for the samples created with additional nitrogen implantation and the control ones. The maximum value of the current-voltage slope also does not experience significant changes. It is shown that in the voltage range from – 0.15 to 0 V, the drain current of nitrogen-implanted samples manufactured using the direct order of heat treatment is higher than for control samples, and the drain current of nitrogen-implanted samples obtained with the reverse order of heat treatment it is lower compared to control samples. Results are explained by a decrease in the density of surface states at the Si – SiO2 interface in MOS-structures created using an additional operation of nitrogen ion implantation in the direct order of heat treatment.

Calculation of error in series/shunt resistance estimated from current–voltage slope using exact analytical expressions with roberts g‐function

The error between the apparent series/shunt resistances of solar cells estimated by the current–voltage slope at the open‐/short‐circuit condition and the true series/shunt resistances is calculated by the exact analytical expressions of the one‐diode equivalent circuit model for the solar cell. In order to avoid the difficulty in computation in known expressions, the exact analytical expressions based on the g‐function proposed by Roberts are derived and employed. Significant deviation is found between the apparent and the true series/shunt resistances. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

What Do Apparent Series and Shunt Resistances in Solar Cell Estimated by I–V Slope Mean? Study with Exact Analytical Expressions

The reciprocal slopes of a current–voltage curve at open‐circuit‐ and short‐circuit‐conditions are frequently mentioned as apparent series (Rs) and shunt (Rp) resistances in emerging solar cell materials research. The relationship between such values and those in the one‐diode equivalent‐circuit model is studied by using exact analytical expressions of the current–voltage slope. It is found that the apparent Rs and Rp significantly deviate from true Rs and Rp.

Deriving the characteristics of warm electrons (100–500 eV) in the magnetosphere of Saturn with the Cassini Langmuir probe

Though Langmuir probes (LP) are designed to investigate cold plasma regions (e.g. ionospheres), a recent analysis revealed a strong sensitivity of the Cassini LP measurements to hundreds of eV electrons. These warm electrons impact the surface of the probe and generate a significant current of secondary electrons, that impacts both the DC level and the slope of the current–voltage curve of the LP (for negative potentials) through energetic contributions that may be modeled with a reasonable precision.We show here how to derive information about the incident warm electrons from the analysis of these energetic contributions, in the regions where the cold plasma component is small with an average temperature in the range ~[100–500]eV. First, modeling the energetic contributions (based on the incident electron flux given by a single anode of the CAPS spectrometer) allows us to provide information about the pitch angle anisotropies of the incident hundreds of eV electrons. The modeling reveals indeed sometimes a large variability of the estimated maximum secondary electron yield (which is a constant for a surface material) needed to reproduce the observations. Such dispersions give evidence for strong pitch angle anisotropies of the incident electrons, and using a functional form of the pitch angle distribution even allows us to derive the real peak angle of the distribution.Second, rough estimates of the total electron temperature may be derived in the regions where the warm electrons are dominant and thus strongly influence the LP observations, i.e. when the average electron temperature is in the range ~[100–500]eV. These regions may be identified from the LP observations through large positive values of the current–voltage slope at negative potentials. The estimated temperature may then be used to derive the electron density in the same region, with estimated densities between ~0.1 and a few particles/cm3 (cc). The derived densities are in better agreement with the CAPS measurements than the values derived from the proxy technique (Morooka et al., 2009) based on the floating potential of the LP. Both the electron temperature and the density estimates lie outside the classical capabilities of the LP, which are essentially ne>5cc and Te<5eV at Saturn. This approximate derivation technique may be used in the regions where the cold plasma component is small with an average temperature in the range ~[100–500]eV, which occurs often in the L range 6.4–9.4 RS when Cassini is off the equator, but may occur anywhere in the magnetosphere. This technique may be all the more interesting since the CAPS instrument was shut down, and, though it cannot replace the CAPS instrument, the technique can provide useful information about the electron moments, with probably even better estimates than CAPS in some cases (when the plasma is strongly anisotropic).Finally, a simple modeling approach allows us to predict the impact of the energetic contributions on LP measurements in any plasma environment whose characteristics (density, temperature, etc.) are known. LP observations may thus be influenced by warm electrons in several planetary plasma regions in the solar system, and ambient magnetospheric electron density and temperature could be estimated in some of them (e.g. around several galilean satellites) through the use of Langmuir probes.

Are Reactive Oxygen Species Generated in Electrospray at Low Currents?

It was demonstrated that electrospraying (ES) of solvents from a glass capillary proceeds without emission of light provided that the current is kept below a certain critical level (<100 nA at positive potential and <25 nA at negative potential for 96% ethanol; < 40 nA at positive potential for water). Though the onset of corona, as detected by the appearance of light, was always accompanied by a break in the current-voltage slope, such breaks also happened before the onset of corona, so they cannot be used as an adequate indicator of corona ignition. Of four ROS studied (hydrogen peroxide, ozone, hydroxyl radicals, and superoxide anions), only H2O2 and ozone were found to be generated at a current of 150-200 nA in detectable quantities: with a yield of 0.5-1 H2O2 molecules per electron at positive potential and 1.5-3 at negative potential. Despite the low yield of the ROS, jack bean urease was shown to be inactivated when the enzyme solution with a concentration below 20 μg/mL was electrosprayed at a current of 200 nA. Addition of 0.1 mM EDTA totally protected the activity of the electrosprayed urease.

Photo-electrochemical properties of nanostructured WO 3 prepared with different organic dispersing agents

Different chemical routes for obtaining nanostructured WO 3 on transparent conductive oxides have been tried by considering the Santato-Augustynski recipe as a main guideline. The preparation started from tungstate salts as precursors and involved different organic dispersing agents. Calcination in air at 550 °C produced the final oxide. Aim of this work is to test the oxide materials as photoanodes for the photo-electrochemical water splitting. WO 3 is a wide bandgap semiconductor, able to transport photogenerated carriers under irradiation, provided that it has a good crystalline structure. The morphology and the crystal size of the obtained WO 3 nanoparticles have been investigated by SEM and XRD. This work shows that the particle size of the WO 3 film decreases with increase in molecular weight of the organic dispersing agents. The current–voltage characteristic curves of WO 3-based electrodes have been obtained by biasing a photo-electrochemical cell with an external voltage ramp, both in the dark and under simulated solar irradiation. Results showed that under incident irradiance a noticeable photocurrent density is obtained with a reasonably steep current–voltage slope and with a plateau current of the order of 1.6–1.8 mA/cm 2 under incident 0.14 W/cm 2 AM 1.5 irradiation.

Effect of current processing on the transport property of the La0.67Ca0.33MnO3 film

Current effect on the transport property of the La0.67Ca0.33MnO3 film has been studied as a function of temperature and magnetic field. The two-lead resistance of the sample shows a strongly asymmetric behavior with respect to current direction after a treatment under a current of the density of ∼1.6×105A∕cm2, and the resistance is much lower in forward direction, the direction of the processing current, than in backward direction. A definite change in current–voltage slope at small but finite forward voltages is observed when alternating the electric field from backward to forward, which is indicative of the presence of two different resistive states corresponding to the two current directions and an energy barrier between these states. The magnetoresistance effect of the two resistive states is significantly different, and it is much stronger for the backward current than for the forward one. This has been proved a combined effect of the inclining of the current–voltage slope and the depression of inter...

Development of an Er–Ni liquid alloy ion source

We have developed a procedure for the fabrication of Er–Ni liquid alloy ion sources. The source is tested and analyzed in a MicroBeam 150 focused ion beam system. Our experimental results show that an Er2+ target current of 95–100 pA was produced, representing 50% of the total target current. The ion emission current–voltage slope is ∼36 μA/kV. Source lifetimes are generally larger than 20 h. The alloy oxidizes quickly once it is exposed to air. This must be minimized to ensure proper source performance.

Dynorphin A decreases voltage‐dependent calcium conductance of mouse dorsal root ganglion neurones.

The actions of the opioid peptides dynorphin A and (Leu)enkephalin were assessed on calcium-dependent action potentials and inward calcium currents recorded from somata of mouse dorsal root ganglion (d.r.g.) neurones grown in primary dissociated cell culture. Dynorphin A and (Leu)enkephalin decreased the duration of somatic calcium-dependent action potentials in a portion of d.r.g. neurones impaled with potassium acetate-filled micropipettes. When substantial potassium conductance was blocked by intracellular injection of caesium acetate, d.r.g. neurones continued to respond to dynorphin A but responses to (Leu)enkephalin were abolished. In voltage-clamp experiments, dynorphin A but not (Leu)enkephalin reduced the magnitude of inward calcium currents. Dynorphin A responses were blocked by the opiate antagonist naloxone. The dynorphin A effect was due to reduction of voltage-dependent calcium conductance since dynorphin A reduced depolarization-evoked inward currents but did not alter membrane conductance following blockade of calcium channels by cadmium, and because dynorphin A reduced the instantaneous current-voltage slope (chord conductance) during step commands that produced maximal activation of voltage-dependent calcium conductance. Dynorphin A binds with high affinity to kappa-opioid receptors. (Leu)enkephalin, which has affinity for both mu- and delta-receptors but not for kappa-opioid receptors, was without effect on calcium conductance. Therefore, we suggest that kappa-receptors are coupled to voltage-dependent calcium-channels and that binding of dynorphin A produces a decrease of calcium current.

Adenosine agonists reduce voltage‐dependent calcium conductance of mouse sensory neurones in cell culture.

Adenosine and several of its analogues produced a concentration-dependent shortening of calcium-dependent action potential (c.a.p.) duration of mouse dorsal root ganglion (d.r.g.) neurones in dissociated cell culture. The following rank order of potency was obtained: N6-(L-phenylisopropyl)adenosine greater than N6-(D-phenylisopropyl)adenosine greater than N6-cyclohexyladenosine greater than 2-chloroadenosine much greater than 1-methylisoguanosine greater than adenosine. Effects of adenosine agonists on c.a.p. duration were blocked by methylxanthine adenosine antagonists. Adenosine monophosphate (AMP) and cyclic AMP shortened c.a.p.s in d.r.g. neurones, while ATP also depolarized cells. Voltage-clamp analysis revealed that the effect arose from reduction of a voltage-dependent calcium conductance. Adenosine agonists reduced depolarization-evoked inward currents but did not alter membrane conductance following blockade of calcium channels by cadmium. Additionally, adenosine reduced the instantaneous current-voltage slope (chord conductance) during step commands that produced maximal activation of voltage-dependent calcium conductance. If effects of adenosine on neuronal somata and synaptic terminals are similar, adenosine agonists may inhibit neurotransmitter release in the central nervous system by inhibiting a voltage-dependent calcium conductance. Since effects of adenosine agonists did not correspond with their relative potencies as modulators of adenylate cyclase activity or inhibitors of neurotransmitter release in peripheral tissues, a novel adenosine receptor may be involved in regulation of this conductance.