Electric Trapping Research Articles

Magnetized electron-whistler holes

Coherent magnetic structures comprising a magnetic vortex and an electron hole have been shown to be created by a Weibel-type, anisotropy driven instability. These structures arise from the electric and magnetic trapping of resonant electrons in the growing fields of the instability. The results of two dimensional Vlasov simulations of the nonlinear development of the instability are compared with a novel analytical model of a stationary propagating phase space structure which includes the depletion of the trapped electrons corresponding to the electron holes.

An assessment of yellow perch, Perca flavescens, stocking contributions in eastern South Dakota lakes

The success and value of yellow perch, Perca flavescens (Mitchill), stocking programmes are largely unknown because of the difficulties in differentiating between naturally recruited and translocated stocks. To determine stocking contributions of yellow perch, fingerlings and adults were collected from natural rearing ponds in south‐eastern South Dakota. Prior to stocking, all fish were marked for 6 h in transfer tanks containing 700 mg L−1 oxytetracycline hydrochloride. Six lakes containing yellow perch populations were supplemented at low, medium and high stocking densities of about 25, 135 or 200 fish ha−1, respectively. Yellow perch populations were subsequently sampled with experimental gill nets during late summer; two lakes were resampled with additional gears (electric fishing, trap nets and cloverleaf traps). Yellow perch were processed for routine measurements, and saggital otoliths were removed to determine the origin of the fish. Stock contribution estimates determined from gill‐net samples for Island (low), Oak (low), Twin (medium) and Wall (high) lakes were approximately 18, 5, 41, and 38%, respectively. Samples from other gears provided stock contributions of 15 and 10% for Cavour Lake and 41% for Diamond Lake (high density stockings). Although these results showed that supplemental stockings were successful, variability in stock contributions among populations indicates a need for further assessment of variables that may influence the stocking success of yellow perch.

On the high-frequency instability of plasma in the octupole galathea electric discharge trap

Spectra of microwave plasma oscillations in an electric discharge trap are considered, and specific features of these spectra related to the instability of transverse current near the magnetic barrier confining the plasma are revealed. A relation between oscillations of the discharge current and the modulation of intensity of the microwave oscillations is established which indicates that the barrier region of discharge possesses an anomalous resistivity.

New defect spectroscopies

This paper will review progress being made on developing more defect selective forms of positron annihilation spectroscopy (PAS) at the University of Hong Kong. The first of these, positron deep-level transient spectroscopy (PDLTS), parallels conventional deep-level transient spectroscopy (DLTS) except that the positron is used as the probe, either to tell if the defects have vacancies attached to their microstructure (type I PDLTS) or as a simple electric field probe (type II PDLTS). It is shown the more important type I PDLTS has an intrinsic problem brought about by the high donor densities required to operate electrical trap filling. The problem—namely fast positron drift out of the active deep-level region into the reverse biased junction—is suggested as having two solutions. The first is to move to higher positron beam intensities and take spectra of 10 9 events. The second is that by using lower dopant densities (<10 15 cm −3) deep levels may be filled by inter-band optical excitation thus forming the workable technique positron optical (PO)-DLTS. Other techniques briefly considered in this paper are deconvoluted-coincidence Doppler broadening spectroscopy (CDBS) and Fourier transform (FT)-CDBS. Such are seen from a different perspective than most contemporary works, which tend to concentrate on the high momentum region. It is pointed out that the additional root-of-two improvement in hardware resolution and the factor of three improvement gained through deconvolution, can produce final effective resolutions similar to ACAR. Moreover, since in deconvolution, the natural space for regularized solutions is “real crystal space”—it is suggested that the autocorrelation function B 2 γ ( r ) be taken as the experimental CDBS data—not just because it provides easier visualization,—but because data in this form lies directly on the crystal lattice.

Comparison of trapping efficacy for Lasioderma serricorne (F.) adults with electric, pheromone, food attractant and control-adhesive traps

During July, August, September and October 1997, in three tobacco stores in the area of Thessaloniki, four types of adhesive traps: electric (black light), pheromone (serricornin and anhydroserricornin), food attractant and control, were used for trapping Lasioderma serricorne (F.) (Coleoptera: Anobiidae). All traps had the same adhesive area based on 29.5×21 cm2 polyethylene sheets. Five replicate comparisons of the four trap types took place. The electric trap caught 8912, the pheromone trap 6608, the food attractant trap 1974 and the control 1231 L. serricorne adults. The electric adhesive trap was significantly more effective than the other traps and the control. The electric trap captured a smaller number of male adults than the pheromone trap but many more females. The ratio between female and male adults was 60.15 : 39.84 for the electric trap, 8.75 : 91.25 for the pheromone trap, 51.57 : 48.42 for the food attractant trap and 43.41 : 56.58 for the control trap.

Estimation of trap levels in SrTiO3 epitaxial films from measurement of (LaSr)MnO3/SrTiO3/(LaSr)TiO3 p-i-n diode characteristics

We have explored electrical trap levels inside SrTiO3 epitaxial films grown by the pulsed laser deposition method from electrical measurements of semiconducting oxide p-i-n diodes consisting of La0.85Sr0.15MnO3/SrTiO3/La0.05Sr0.95TiO3 trilayers. The prepared p-i-n diodes exhibited a marked temperature dependence in their current–voltage (I–V) characteristics. By attributing the temperature dependence of I–V curves to the space-charge limitation due to the trapped charges inside the i-SrTiO3 layer, we estimated crudely the level of the dominant trap in the SrTiO3 layer as ∼0.09 eV. The trap density was also estimated from the curve-fitting technique. At this moment, the trap densities were 1016 and 1018/cm3 when SrTiO3 layers were grown at 650 and 630 °C, respectively.

Role of inversion layer formation in producing low effective surface recombination velocities at Si/liquid contacts

Photoconductivity decay lifetimes have been obtained for NH4F(aq)-etched Si(111) and for air-oxidized Si(111) surfaces in contact with solutions of CH3OH or tetrahydrofuran (THF) containing either ferrocene+/0 (Fc+/0), bis(pentamethylcyclopentadienyl) Fe+/0, or I2. Si surfaces in contact with electrolytes having Nernstian redox potentials &amp;gt;0 V versus the standard calomel electrode exhibited low effective surface recombination velocities regardless of the different surface chemistries, whereas those exposed only to N2(g) ambients or to electrolytes containing mild oxidants showed differing rf photoconductivity decay behavior depending on their different surface chemistry. The data reveal that formation of an inversion layer, and not a reduced density of electrical trap sites on the surface, is primarily responsible for the long charge-carrier lifetimes observed for Si surfaces in contact with CH3OH or THF electrolytes containing I2 or Fc+/0.

Theoretical modelling of CW perturbations of excited states, axialfield and electron density for laser diagnostics of positive columnplasmas

We present a theoretical treatment of the fundamental perturbationscaused when continuous wave tunable laser radiation is absorbed by thelow-temperature plasma of a noble gas positive column. For the first time wepresent a full theoretical description of the contributions due to the inducedchanges in the electric field, electron density and radiation trapping, aswell as the primary laser perturbations. Comparison of our theory withexperimental observation shows that the primary perturbations are generallydominant but in some instances it is the field perturbation which has thegreatest effect.

Highly charged ions produced in a warm electron beam ion trap

A compact electron beam ion trap (WEBIT) working at room temperature without any cryogenic components is described and experimentally investigated. The trap design is based on permanent magnet technology. For the formation of the electron beam a Pierce electron gun equipped with a cathode of high emissivity is used. The ion trap is created by a compressed electron beam passing through a drift tube system consisting of three sections with corresponding electrical trap potentials. X-ray spectra measured with a Si(Li) semiconductor detector indicate the production of Kr34+, Xe44+, Ce48+, Ir64+, and Hg66+ ions.

A novel electric ion resonance cell design with high signal-to-noise ratio and low distortion for Fourier transform mass spectrometry

Performing wideband ion image current detection mass spectrometry experiments with an electric ion trap—e.g., the Paul trap—is a difficult task, as there is a strong crosstalk current induced by the high voltages of the radio frequency (rf) storage field. In a classic Paul trap the metallic hyperbolic electrodes (a ring electrode and two end cap electrodes) are shaped following the isopotential lines of the quadrupole potential distribution. In our new design the ring electrode is replaced by a cylindrical series of ring electrodes with a parabolic potential distribution, whereas the end cap electrodes are used without modification. Thus the quadrupole field within the trap remains unchanged but the capacitances between the electrodes and therefore the crosstalk currents are significantly reduced. The remaining crosstalk is balanced out by an electronic compensation technique. As a consequence the weak signals of the ion-induced charge can be detected with a wideband low-noise amplifier to perform Fourier transform mass spectrometry experiments with improved signal-to-noise ratio.

Improved reliability of NO treated NH 3-nitrided oxide with regard to O 2 annealing

NH 3-nitrided oxide has been annealed in NO or O 2 gas at 1000°C for 1 min and the electrical characteristics, charge trapping and time-dependent dielectric breakdown (TDDB) have been studied. It was observed that in the F–N region before stress the conduction current is the same for all the samples but intrinsic breakdown is earlier for O 2 annealed NH 3-nitrided oxide. After stress, the leakage current increases abruptly for the O 2 annealed NH 3-nitrided oxide. The TDDB characteristics have been measured for wet, NO and O 2 annealed NH 3-nitrided oxide. It was observed that the endurance of wet and NO annealed NH 3-nitrided oxide is the same, but the O 2 annealed NH 3-nitrided oxide has a lot of initial failure at the same stress of −11 MV cm −1. From the experimental results, it can be said that NO annealing not only removes H which comes from the NH 3 nitridation but also improves the oxide reliability by replacing strained Si–O bonds for a stable Si–N bond.

Electrical transport and trap properties in nitrogen-doped p-type MBE-grown ZnSe layers on GaAs using different contact materials

Electrical transport and trap properties were studied for nitrogen-doped p-type ZnSe layers grown on GaAs by molecular beam epitaxy (MBE). IV, CV and DLTS measurements were performed using gold, aluminium and indium dots as metal electrodes for the formation of Schottky contacts. In order to investigate the influence of thermal treatment on the defect properties of the ZnSe layers, the samples were annealed in vacuum at temperatures between 350 and 600 K. A strong hole-trap generation process is observable at temperatures higher than 500 K after annealing times exceeding 10 min. Moreover, annealing at 600 K leads to significant hole compensation caused by large trap concentrations generated at this temperature.

Electrical transport and trap properties in nitrogen-doped p-type MBE-grown ZnSe layers on GaAs using different contact materials

Electrical transport and trap properties in nitrogen-doped p-type MBE-grown ZnSe layers on GaAs using different contact materials

Ion trap for mass-selective production of nanoclusters

To form nanoclusters with a specified atomic structure, an electrical trapping technique of charged particles was developed that allows us to confine, grow, and mass selectively eject cluster ions. Theoretical calculations and experiments using inert gas ions indicate that the developed ion trap can confine ions with a wide range of mass values using the external field of an ac quadrupole, and send out the ions mass selectively through the internal region of the quadrupole. To demonstrate performance, Si6H12+ clusters were selectively grown using SiH4 as a starting material. In the trap, confined SiHx+ ions were allowed to react with neutral SiH4 molecules or SiHy radicals, and SinHx+ clusters were grown, from which Si6H12+ clusters were automatically ejected by tuning trapping parameters.

Nitrogen Doped ZnSe Layers on GaAs

Nitrogen doped p-type ZnSe layers grown on GaAs by molecular beam epitaxy (MBE) are studied with regard to their electrical transport and trap properties. Gold, aluminium and indium dots are used as metal electrodes for the formation of Schottky contacts in order to measure the IV, CV and DLTS characteristics. A strong hole trap generation is observed after a vacuum annealing as well as due to a constant current stress. The concentration of a dominant hole trap with an activation energy of about 0.65 eV is drastically increased especially after a thermal treatment at temperatures higher than 500 K. Furthermore, as a result of annealing experiments the electrode materials are found to influence the rate of trap generation. A diffusion induced defect generation mechanism seems to be responsible for the observed increase of trap concentration and the related decrease of effective acceptor doping concentration.

An experiment to purify diesel exhaust gas using an electric trap and three types of catalysers

Diesel engine exhaust gas is known to be one cause of photochemical smog, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a series of experiments to assess the purifying effects of a diesel gas purification device employing an electric trap. It has been confirmed that an extraction rate of 60 ∼ 75 % for black smoke can be achieved using this apparatus, but the extraction effect for nitrogen oxides (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken using the same device in combination with various types of attached catalysers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obtained. Nor was any significant result observed from the use of an ozoniser. However, with a zeolyte catalyser, it was possible to achieve a NOx reduction of 20 ∼ 30 %. This latter experiment is reported in the present paper.

Purification of Diesel Exhaust Gas Using Reducing Catalysers

AbstractDiesel engine exhaust gas is known to be one cause of photochemical smog, which is so damaging to city environments. However, because of its high thermal efficiency and economic advantages, the diesel engine is not easily dispensable. The authors have previously conducted a series of experiments to assess the purifying effects of a diesel gas purification device employing an electric trap. It has been confirmed that an extraction rate of 60∼75 % for black smoke can be achieved using this apparatus. But the extraction effect for nitrogen oxides (NOx) is insufficient if the electro-trap device is used on its own. To improve its performance, experiments have now been undertaken using the same device in combination with various types of attached catalysers to oxidise and remove the nitrogen in the exhaust gas. Utilising a commercial 3-way catalyser, it proved difficult to maintain the gas at a suitable temperature, so that no outstanding result could be obtained. Nor was any significant result observ­ed from the use of an ozoniser. However, with a zeolyte catalyser, it was possible to achieve a NOx reduction of 20∼30 %. This latter experiment is reported in the present paper.

Near room temperature energy‐dispersive detectors processed on high‐purity silicon

AbstractDiode detectors and silicon drift chambers were processed on TOPSIL high‐purity silicon of resistivity 7 kΩ cm. Their suitability for XRF spectroscopy, when cooled to −30°C, was evaluated. The efficiency for different x‐ray energies was calculated starting from the processing parameters used in manufacturing. Spectrum measurements were made in order to establish the mechanisms causing electrical noise and charge trapping. With an 18 mm2 active area detector it was possible to achieve an FWHM of 385 eV for the 55Fe source 5.89 keV peak and better than 300 eV with detectors of 1 mm2 area. Incomplete charge collection was found to be due to effects on the edge of the detector active area or in the implanted surface facing the radiation.

Evolution of trapped ion cells in Fourier transform ion cyclotron resonance mass spectrometry

Factors shaping the development of trapped ion cells in Fourier transform ion cyclotron resonance (FTICR) mass spectrometry have evolved along several lines. Areas of improvement include maximizing the quadrupolar character of the cell, reducing the radial electric trapping field, and improving the linearity of the excitation event. This review focuses on cell development for optimum FTICR performance.

Transient and Steady State Carrier Transport under High Field Stresses in SONOS EEPROM Device

The carrier transport model of tunneling oxide in a polysilicon-oxide-nitride-oxide-silicon (SONOS) device has been developed. The model is deduced from WKB approximation, and uses Fermi-Dirac statistics. Using the J-E and accompanied by Arnett's trapping model, the switching behavior of the SONOS device can be predicted in a very wide range of switching times from 1 µs to 0.1 s. The steady-state charge distribution and electric field in Si3N4 are also calculated. From Arnett's fundamental equations of Si3N4, we deduce the steady-state equations which describe the electric field and trapping charges. The trapping parameters and detrapping factor ν are discussed and the results are obtained via computer for different temperatures and stress voltages, which are based on the current measurement of SONOS devices. We find that the detrapping effect is somewhat less dominant compared to the trapping effect in our simulations.