Ion Current Ratio Research Articles

Optimisation of fully depleted SiGe channel with raised source/drain buried oxide nMOSFET

A fully depleted silicon-germanium (SiGe) n-channel heterojunction MOSFET with raised buried oxide in the source/drain is reported under the consideration that channel is made of SiGe and source/drain regions is made of silicon (Si). Due to the raised buried oxide source/drain region, it provides better current due to the improvement of mobility in the channel region and also reduce the surface scattering effects. Bandgap engineering has been done to improve the electrical behaviour of the device. Simulation work for different parameters on the device has been carried out and presented in the paper. The electrical characteristics of the proposed device are optimised by varying the device dimensions. Effect of mole fraction on threshold voltage (VTH), Subthreshold swing (SS), ION and IOFF current ratio is analysed. It is observed that due to presence of SiGe channel and the raised source/drain, the proposed device shows enhancement in electrical characteristics. A CMOS inverter through proposed device has been implemented and the effect of mole fraction on its characteristic is reported. Average delay increases as mole fraction increases.

GDMS Analysis Of Calcium Carbonate Naturaly Doped By REE, Phospates And Other Impurities

A mathematical model was developed for calculation of types and intensities of molecular interferences and simulation of mass-spectra at GDMS analysis of non-conducting samples with the use of a secondary cathode. An improved design of the cell with Ta-secondary cathode were suggested enhancing the matrix to tantalum ion current ratio and sensitivity of the analysis in ca. 1.5 orders of magnitude. The model have been used for interpretation of complicate mass-spectra of calcium carbonate naturally doped with REE, phosphates and other impurities. Comparison calculated and experimental mass-spectra of VG9000 instrument demonstrates good agreement and allows select the most suitable isotopes and rejecting wrong molecular peaks. It have been shown that electrons in glow discharge plasma have different temperatures in different zones that reveals itself as separate Boltzmann populations of ionization levels for molecules, metal atoms and argon atoms/ions. Calcium carbonate is widely used for many application including as precursor for nano-hydroxyapatite synthesis. Calcium carbonate was precipitated from natural mine waters and was used as model object having high number of various impurities allowing to investigate the impact of complicate molecular ions, determine necessary resolving power of the GD-instruments to meet required detection limit.

Comprehensive chemical characterization of lubricating oils used in modern vehicular engines utilizing GC × GC-TOFMS

A number of major studies have demonstrated that the SVOC (Semi-volatile organic compounds) within engine emissions derive predominantly from unburned fuel and lubricants, and are a major contributor to primary atmospheric aerosol containing thousands of organic compounds. The GC × GC-ToF-MS (2 dimensional Gas Chromatography – Time of Flight – Mass Spectrometry) comprehensive analytical technique was utilized in this study, to resolve the complex mixtures and characterize the SVOC content in eight different commercial lubricants, including 5 W30 synthetic and semi-synthetic, mineral and base oil. In order to quantify the aliphatic isomers, which comprise the largest component of the lubricants, a TIC-M.Q./Mass (Total ion current ratio to the molar quantity/mass) method has been developed. The TIC intensity was observed to be proportional to the molar quantity of n-alkanes for carbon number <C25, while being linear to the mass response for these aliphatic compounds with carbon number >C25. Additionally, the TIC intensity of the alkyl-cyclohexanes under the identical retention indices were found to have an equivalent response to those of the n-alkanes, showing that the quantitative calibrations derived for the n-alkane series could be applied to estimate the concentrations of isomeric aliphatic compounds with similar molecular weight. Furthermore, a mesh method was introduced to group the alkane species (n-alkanes, branched alkanes and cyclic alkanes etc.), combining with the use of a soft EI (electron impact) ionization (14 eV) to retain the distinct identity of the isomers with less fragmentation, which allowed the TIC-M.Q./Mass methodology to integrate all the constitutional isomers present in the lubricating oil samples. By utilizing this methodology, compositions from different samples were comprehensively compared, leading to the following conclusions: 1) the synthetic and semi-synthetic oils contained a larger abundance of HMW (high molecular weight) aliphatic compounds (carbon number C24–C29), while those in the LMW (low molecular weight range, carbon number C18–C25) were predominant in the mineral and base oil; 2) cycloalkanes were predominant in the synthetic and semi-synthetic oils; whereas the branched alkanes were more prominent in the mineral and base oils; 3) for lubricants used for a short period, a slight increase of LMW compounds was observed, while the HMW compounds underwent a decrease, whereas, there was an overall mass reduction for all the aliphatic compounds detected in the oil samples used for six-months.

Ozone-free post-DBD aerosol bipolar diffusion charger: Evaluation as neutralizer for SMPS size distribution measurements

ABSTRACTA postplasma neutralizer for submicron particles size measurements by mobility analysis has been evaluated. Bipolar ion currents have been measured downstream a dielectric barrier discharge (DBD) to estimate the ion fluxes at the inlet of charging volume and the ni·τ product that define the theoretical maximal concentration that can be neutralized. Charge distributions were measured versus DBD voltage, aerosol diameter and concentration for monodisperse aerosols. It is confirmed that the charge distribution of particles depends on the ratio of initial positive and negative ion currents controlled by the DBD voltage leading to a tuneable mean charge of aerosol in this post-DBD bipolar charger. As expected from Gunn's law, the mean charge and the variance are proportional to particle diameter above 50 nm and independent of the aerosol concentration. The size distributions measured with 85Kr and post-DBD neutralizer present the same modal diameters and a maximal overestimation of the total concentrat...

Influence of Plasma Assistance on Arc Deposited MoN Coatings

The paper reports on a study to optimize the modes of plasma-assisted vacuum arc deposition of molybdenum nitride (MoN) coatings. It is shown that the parameters of plasma assistance influence the coating properties and that varying the ion current ratio in the metal-gas plasma makes possible MoN coatings with high hardness and high wear resistance.

Simultaneous DC measurements of ion current density and electron temperature using a tunnel probe

The tunnel probe is a concave Langmuir probe designed to operate in strongly magnetized plasma. Due to its shape, the tunnel probe is immune to sheath expansion effects and thus provides absolutely calibrated measurements of the parallel ion current density. A two-dimensional, self-consistent kinetic model is employed to model the flow of charges within the cavity of the tunnel probe. The calculation predicts that the distribution of the ion flux onto the inner conductors depends on the electric field inside the tunnel, which in turn depends on the electron temperature. Therefore, if the tunnel is divided into two negatively biased collectors, it is possible to use the simulation results to determine the electron temperature from the measured ion current ratio. This means that a DC-biased tunnel probe can be used to provide fast, simultaneous measurements of the parallel ion current density and the electron temperature without collecting a single electron. Measurements in the CASTOR and Tore Supra tokamaks agree well with the numerical simulations.

Ultrasensitive determination of mercury(II) using glass nanopores functionalized with macrocyclic dioxotetraamines

Glass conical nanopores functionalized with a macrocyclic dioxotetraamine derivative (C5) are shown to enable ultrasensitive determination of Hg(II). A complex is formed between Hg(II) and C5, and this converts the functionalized glass nanopore from a rectifying state to a non-rectifying state. The presence of Hg(II) in ~10 pM levels or higher can be detected by measuring the ion current rectification ratio in voltage range of ± 500 mV. This sensing strategy opens new possibilities for development of a simple, portable and convenient device for the quantitation of Hg(II) with very low limits of detection.

Sugar-stimulated robust nanodevice: 4-Carboxyphenylboronic acid modified single glass conical nanopores

In this work, we demonstrate a smart robust nanodevice that rectifies the ion current in response to sugar stimulation. The response is achieved by immobilizing 4-carboxyphenylboronic acid to the wall of a single glass conical nanopore. This smart robust nanodevice shows excellent sugar responsive capacity with the switch between the non-rectifying and rectifying states of the ion transport properties. The ion current rectification ratio increases linearly with increasing concentration of glucose and correlates to the concentration of the target by a simple linear regression equation, which makes quantitative nanosensing easily accessible for application in biomedical fields.

A double-plasma source of continuous bipolar ion-ion beam

A double-plasma source capable of the generation of a continuous bipolar ion-ion beam is described. The quasi-neutral ion-ion flow to an extraction electrode is formed in the system containing primary inductively coupled plasma separated from a secondary plasma by an electrostatic grid-type filter. The total current of each ion species to the 250 mm diameter extraction electrode is about 80 mA; the electron current does not exceed 30% of the ion current. Method of positive/negative ion current ratio control is proposed, allowing the ion currents ratio variation in wide range.

Negative ion test facility ELISE—Status and first results

The new test facility ELISE (Extraction from a Large Ion Source Experiment) has been designed and installed since November 2009 at IPP Garching to support the development of the radio frequency driven negative ion source for the Neutral Beam System on ITER. The test facility is now completely assembled; all auxiliary systems have been commissioned and are operational. First plasma and beam operation is starting in October 2012.The source is designed to deliver an ion beam of 20A of D− ions, operating at 0.3Pa source pressure at an electron to ion current ratio below 1. Beam extraction is limited to 60kV for 10s every 3minutes, while plasma operation of the source can be performed continuously for 1hour. The ion source and extraction system have the same width as the ITER source, but only half the height, i.e. 1×1 m2 source area with an extraction area of 0.1 m2. The aperture pattern of the extraction system and the multi driver source concept stay as close as possible to the ITER design. Easy access to the source for diagnostic tools or modifications allows to analyze and optimize the source performance. Among other possibilities many different magnetic filter field configurations inside the source can be realized to enhance the negative ion extraction and to reduce the co-extraction of electrons. Beam power and profiles are measured by calorimetry and thermography on an inertially cooled target as well as by beam emission spectroscopy. Cs evaporation into the source is done via two dispenser ovens.

Generation of negative ions from SF6 gas by means of hot surface ionization

Sulfur hexafluoride (SF(6)) is a man-made compound with many industrial applications. This compound is also one of the most powerful greenhouse gases with a relatively long atmospheric lifetime. Therefore, it is important to investigate processes leading to SF(6) decomposition. A magnetic sector mass spectrometer with a thermoemission gaseous ion source was used in this study. The filament temperature was changed and monitored pyrometrically during the course of the studies. In the hot surface ionization process, negative ions may be generated both by free electron attachment to a molecule and by thermal dissociation followed by electron capture to the one of the fragments formed. Eight ion species: SF(5)(-), F(-), SF(6)(-), SF(4)(-), SF(3)(-), SF(2)(-), SF(-) and F(2)(-), with ion current intensities ratios of 1000:200:100:10:5:0.5:0.5:0.05, respectively, were detected. The filament temperature dependencies of the SF(5)(-), F(-), SF(6)(-), SF(4)(-) ion current intensities were measured. The optimal temperatures at which the maximum of the ion current intensity is observed were estimated in the 1830-2000 ± 10 °C range. The formation of F(2)(-) ions is probably disturbed by a dissociation process at high temperatures. Negative surface ionization on the hot filament is a relatively simple and effective method for carrying out negative ion formation studies. Eight SF(6) decomposition channels leading to the formation of negative ions have been detected and analyzed using this technique.

Ion diode logics for pH control

Electronic control over the generation, transport, and delivery of ions is useful in order to regulate reactions, functions, and processes in various chemical and biological systems. Different kinds of ion diodes and transistors that exhibit non-linear current versus voltage characteristics have been explored to generate chemical gradients and signals. Bipolar membranes (BMs) exhibit both ion current rectification and water splitting and are thus suitable as ion diodes for the regulation of pH. To date, fast switching ion diodes have been difficult to realize due to accumulation of ions inside the device structure at forward bias--charges that take a long time to deplete at reverse bias. Water splitting occurs at elevated reverse voltage bias and is a feature that renders high ion current rectification impossible. This makes integration of ion diodes in circuits difficult. Here, we report three different designs of micro-fabricated ion bipolar membrane diodes (IBMDs). The first two designs consist of single BM configurations, and are capable of either splitting water or providing high current rectification. In the third design, water-splitting BMs and a highly-rectifying BM are connected in series, thus suppressing accumulation of ions. The resulting IBMD shows less hysteresis, faster off-switching, and also a high ion current rectification ratio as compared to the single BM devices. Further, the IBMD was integrated in a diode-based AND gate, which is capable of controlling delivery of hydroxide ions into a receiving reservoir.

Si primary standards for the calibration of ion-current ratios in the molar-mass measurement of natural Si single crystals

A procedure is described to obtain SI-traceable silicon isotope amount ratios in the BaSiF6 form. On the basis of a gravimetric approach, three synthetic isotope mixtures were made, very similar to natural Si, by blending silicon isotopically enriched with 28Si, 29Si and 30Si. These mixtures served as references to calibrate measurements of (SiF3)+ current ratios. In this way, it was possible to make SI-traceable measurements of silicon isotope amount ratios, without any assumptive correction. The isotopic composition of the natural Si crystal WASO17.2 was remeasured and its molar mass was redetermined.

A study of the plasma electronegativity in an argon–oxygen pulsed-dc sputter magnetron

Using Langmuir probe-assisted laser photodetachment, the temporal evolution of the O− density was determined in the bulk plasma of a unipolar pulsed-dc magnetron. The source was operated in reactive mode, at a fixed nominal on-time power of 100 W, sputtering Ti in argon–oxygen atmospheres at 1.3 Pa pressure, but over a variation of duty cycles from 5% to 50% and oxygen partial pressures of 10% and 50% of the total pressure.In the plasma on-time, for all duty cycles the negative ion density (n−) rises marginally reaching values typically less than 2 × 1015 m−3 with negative ion-to-electron density ratios, α < 1. However, immediately after the transition from pulse on-to-off, n− falls by about 20–30% as fast O− species created at the cathode exit the system. This is followed by a rapid rise in n− to values at least 2 or 3 times that in the on-time. The rate of rise of n− and its maximum value both increase with decreasing duty cycle. In the off-time, the electron density falls rapidly (initial decay rates of several tens of μs), and therefore the afterglow plasma becomes highly electronegative, with α reaching 4.6 and 14.4 for 10% and 50% oxygen partial pressure, respectively. The rapid rise in n− in the afterglow (in which the electron temperature falls from about 5 to 0.5 eV) is attributed to the dissociative attachment of highly excited oxygen metastables, which themselves are created in the pulse on-time. At the lowest duty of 5%, the long-term O− decay times are several hundred μs.Langmuir probe characteristics show the clear signature that negative ions dominate over the electrons in the off-time. From the ion and electron saturation current ratios, α has been estimated in some chosen cases and found to agree within a factor between 2 and 10 with those obtained more directly from the photodetachment method.

Reversible Cobalt Ion Binding to Imidazole-Modified Nanopipettes

In this report, we demonstrate that quartz nanopipettes modified with an imidazole-terminated silane respond to metal ions (Co(2+)) in solution. The response of nanopipettes is evaluated through examination of the ion current rectification ratio. When nanopipettes are cycled between solutions of different pH, adsorbed Co(2+) can be released from the nanopipette surface, to regenerate binding sites of the nanopipette. These results demonstrate that rectification-based sensing strategies for nanopore sensors can benefit from selection of recognition elements with intermediate binding affinities, such that reversible responses can be attained.

Particle‐In‐Cell Simulations of the Ball‐Pen Probe

AbstractIn this paper, we present results of Particle‐In‐Cell simulations of a simplified model of the Ball‐pen probe (BPP). The BPP is a probe designed for direct measurements of plasma potential in the scrape‐off layer (SOL) of tokamaks. The probe is based on a standard Langmuir theory, which states that when the ratio of ion and electron saturation currents flowing to the probe collector approaches zero, the floating potential of the collector is close to the plasma potential. However, it is unclear whether the Langmuir theory is still valid in such a complex geometry, where the probe tunnel can work as a filter in velocity phase‐space and as such violates the Maxwellian distributions of particle velocities. To verify the validity of the theory a simplified model of BPP has been studied using the SPICE2 code (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Preparation of argon Primary Measurement Standards for the calibration of ion current ratios measured in argon

In this work a procedure is described to prepare SI-traceable argon isotope amount ratios in high purity argon. Following a gravimetric approach, a total of three synthetic isotope mixtures have been prepared, from argon gases enriched in 36Ar, 38Ar and 40Ar, close to the natural isotopic composition of argon. These synthetic mixtures serve as reference gases to calibrate ion current ratio measurements in argon. In this way SI-traceable measurements of argon isotope amount ratios can be performed without any assumptive correction. On a high purity argon gas separated from air the absolute argon isotope amount ratios R 36/40 = 0.00334774 (93) and R 38/40 = 0.00063529 (57) were measured. From these ratios, the average molar mass of argon gas can be determined with a total relative combined uncertainty of 0.09 × 10 −6.

Simultaneous Measurement of 17β-Estradiol, 17α-Estradiol and Estrone by GC-Isotope Dilution MS/MS.

A convenient GC-MS/MS-based method was developed for the simultaneous measurement of 17β-estradiol, 17α-estradiol and estrone using liquid-liquid extraction, a single-step derivatization with N-(trimethylsilyl)imidazole and the corresponding deuterated estrogens as internal standards. Separation of these estrogens was achieved on a 50% phenyl polysilphenylene-siloxane bonded phase column. MS/MS response factors for the derivatized analytes and their corresponding internal standards were found to be practically identical. Therefore, analyte concentrations could be determined by multiplying the measured analyte to internal standard ion-current ratio with known molar concentration of the corresponding deuterated internal standards. Assay accuracies, determined from the analyses of quality control samples obtained by spiking known concentrations of analytes into charcoal-stripped human serum, were in the -11% to +14% range. Limits of quantitations were between 13 pg/mL and 21 pg/mL from this biological medium.

The Effect of Adding Insulating-Nanoparticles to Nematic Liquid Crystal Cells on Ion Current and Voltage-Holding Ratio

The transient currents induced by an applied direct voltage (DC) electric field have been measured in the nematic phase of liquid-crystal cells. The experimental results show that the addition of insulating nano-particles such as diamond powders, leads to a decrease in the ion concentration in cells so as to reduce transient currents and threshold voltage drastically. Simultaneously, a high voltage-holding ratio (VHR) is observed in doped cells. Such a high VHR, in comparison with the one in nematic liquid crystals doped by carbon nanotubes, is a superior feature for future liquid crystal display applications.

Continuous High-Frequency Dissolved O2/Ar Measurements by Equilibrator Inlet Mass Spectrometry

The oxygen (O(2)) concentration in the surface ocean is influenced by biological and physical processes. With concurrent measurements of argon (Ar), which has similar solubility properties as oxygen, we can remove the physical contribution to O(2) supersaturation and determine the biological oxygen supersaturation. Biological O(2) supersaturation in the surface ocean reflects the net metabolic balance between photosynthesis and respiration, i.e., the net community productivity (NCP). We present a new method for continuous shipboard measurements of O(2)/Ar by equilibrator inlet mass spectrometry (EIMS). From these measurements and an appropriate gas exchange parametrization, NCP can be estimated at high spatial and temporal resolution. In the EIMS configuration, seawater from the ship's continuous intake flows through a cartridge enclosing a gas-permeable microporous membrane contactor. Gases in the headspace of the cartridge equilibrate with dissolved gases in the flowing seawater. A fused-silica capillary continuously samples headspace gases, and the O(2)/Ar ratio is measured by mass spectrometry. The ion current measurements on the mass spectrometer reflect the partial pressures of dissolved gases in the water flowing through the equilibrator. Calibration of the O(2)/Ar ion current ratio (32/40) is performed automatically every 2 h by sampling ambient air through a second capillary. A conceptual model demonstrates that the ratio of gases reaching the mass spectrometer is dependent on several parameters, such as the differences in molecular diffusivities and solubilities of the gases. Laboratory experiments and field observations performed by EIMS are discussed. We also present preliminary evidence that other gas measurements, such as N(2)/Ar and pCO(2) measurements, may potentially be performed with EIMS. Finally, we compare the characteristics of the EIMS with the previously described membrane inlet mass spectrometry (MIMS) approach.