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The nanoscaled profiling of a silicon 5 (111) n-type substrate surface is studied by the local anodic oxidation (LAO). Varying the voltage pulse amplitude from 5 to 12.5 V and the humidity from 30 ± 1 to 70 ± 1% during the LAO is a promising way to form oxide structures with heights from 0.5 ± 0.3 to 2.1 ± 0.1 nm and profiled structures with depths from 0.4 ± 0.3 to 1.5 ± 0.2 nm on the substrate. The results can be applied to the development of technological processes of the element base of silicon-based nanoelectronics using the probe nanotechnologies.

The effect of applying a positive voltage pulse (Urev = 10 - 150 V) directly after the negative high power impulse magnetron sputtering (HiPIMS) pulse (bipolar HiPIMS) is investigated for the reactive sputter deposition of TiN thin films. Energy-resolved mass spectroscopy analyses are performed to gain insight in the effect on the ion energy distribution function of the various ions. It is demonstrated that the energy of a large fraction of the ions can be tuned by a reverse target potential and gain energy corresponding to the applied Urev. Microscopy observations and x-ray reflectometry reveal densification of the films which results in an increase in the film hardness from 23.9 to 34 GPa as well as an increase in compressive film stress from 2.1 GPa to 4.7 GPa when comparing conventional HiPIMS with bipolar HiPIMS (Urev = 150 V).

Single Co adatoms adsorbed on a double-layer NaCl film supported by Cu(111) were negatively charged after applying a positive voltage pulse to the sample in a scanning tunnelling microscope. Density functional calculations showed that the magnetic moment of Co changed from 3μB to 2.2μB after charge state manipulation.

Slow deformation seriously restrains application development of IPMC actuator, especially for thick and ionic liquid-based IPMC. Inspired by the action potential of muscle cell, this letter proposes a concept of high electrical pulse stimulus to accelerate IPMC deformation. By analyzing the dynamic process of voltage drop at the electrode-polymer interface, high voltage pulse is proved theoretically to be safe for IPMC in a short time. After charging the electrical double layer at the interface, the voltage pulse should be reduced to a safe level before electrochemical reactions. In our experiments, applying various high voltage pulses to a thick IPMC, the deformation can be sped up a few hundred times at most without any electrolysis damage. The results strongly support the practicability of the impulsive driving method.

A model for the oxide nanostructures formation by the local anodic oxidation method is presented. Dependences of height, depth, and diameter of titanium oxide nanostructures on the applied voltage pulse duration are obtained, as well as the oxide nanostructures profile for given technological parameters.

A temperature model of the phase change memory (PCM) cell having Ge 2 Sb 2 Te 5 (GST) layer has been proposed and demonstrated based on a thermal physical model and electrical characteristics. Calculating the radius of PCM cell with different reset voltage pulse based on the voltage–current curves by the temperature equation, the crystalline fraction can be got. It is found that the crystalline fraction and temperature of active region increase with the reset voltage pulse increasing. The experimental results are consistent with the simulation results.

The effect of voltage exceeding Vmin, the voltage corresponding to the local current minimum, on organic bistable devices is investigated. It is found that when the termination voltage VT exceeds Vmin, with the increasing VT, the bistable effect gets worse and finally lost at VT about 2Vmin. However, the bistable effect can be recovered by applying a voltage pulse with amplitude near Vmin for milliseconds or longer. The existence of localized conducting micro-channels is suggested to account for the bistable effect.

A series of La0.7Ca0.3MnO3 films are fabricated by pulsed laser deposition under controlling the oxygen partial pressure or adding an oxygen post-annealing process. The film after oxygen post-annealing shows an orientation change and has more non-lattice oxygen near the surface than those of the films without annealing. Moreover, only the structure of Ag/La0.7Ca0.3MnO3/Pt with the oxygen annealed film behaves a big current-voltage hysteresis and stable resistance switching properties by applying voltage pulse. Experimental results indicate that the increase of non-lattice oxygen content induced by oxygen annealing in the vicinity of the Ag/La0.7Ca0.3MnO3 interface contributes to the occurrence of resistance switching. And with the accurate controlling of the oxygen annealing parameters, the improvement of resistance switching property of the La0.7Ca0.3MnO3 film can be expected.

International audience; We propose in this paper novel approach for improving mass resolution in atom probe tomography. Using conventional counter-electrode or microelectrode design, improved mass resolution at half, tenth and 1% of the mass peak maximum is predicted when shaping properly the voltage evaporation pulse. Using a numerical approach, it is shown that a flat top voltage pulse used to trigger the field evaporation with sharp front and leading edges associated with a short tip to counter electrode distance(≈10 μm) strongly minimizes the energy deficits of evaporated ions from the sample, so that energy compensation devices are not necessary to obtain high mass resolution.

A near contact atomic force microscope operated at low-temperature is used for vertical and lateral atom manipulations of selected single atoms on semiconductor surface. The precisely controlled short-range chemical force interaction during a soft nanoindentation with the tip apex atom close to the surface leads to the removal and lateral manipulation of a selected surface adatom, and deposition of a single atom on a selected vacancy at the surface. Besides, the precisely controlled short-range chemical force interaction during a near contact raster scan leads to the sequential lateral atom manipulation. These manipulation processes are purely mechanical, since neither bias voltage nor voltage pulse is applied between probe and sample. Using these different two methods, surface atomic structures on the selected regions were successfully modified. [DOI: 10.1380/ejssnt.2006.1]

A thermochemical hole burning (THB) effect was observed on two organic charge transfer complexes, when applying a suitable voltage pulse using a scanning tunneling microscope (STM), which is closely related to a STM current-induced localized thermochemical decomposition of the charge-transfer complex. The decomposition reaction evolves the low boiling point decomposition components of the charge-transfer complex, leaving a nanometer-sized hole on the crystal surface. This effect demonstrates the possibility of creating an ultrahigh-density THB memory, in which information bit is recorded as a hole.

Previous studies have reported that mature oligodendrocytes (OLGs) in vitro display various voltage-dependent K+ currents while in situ OLGs show only voltage-independent K+ currents. Given this discrepancy and the lack of information on myelinating OLG ion channel expression in situ, we characterized mature OLG currents in myelinating corpus callosum slices from 17 to 36-day old rats. OLGs were recorded in cell-attached and whole-cell patch-clamp configurations, displayed morphology typical of mature OLGs, and stained positive for myelin basic protein. OLGs displayed large voltage-independent currents that decayed during the voltage pulse and small voltage-activated outward currents. The latter were blocked by TEA, activated between -40 and -50 mV, and decayed slowly. The former were composed of large voltage-independent, time-dependent Ba2+ (1 mM)-sensitive currents, and voltage-dependent Cs+ (5 mM) and Ba2+ (100 mM)-sensitive currents that reversed near the K+ equilibrium potential and inactivated at hyperpolarized potentials, identifying them as inwardly rectifying K+ currents. Inwardly rectifying single-channel K+currents could be recorded in the cell-attached configuration. The estimated single-channel slope conductance was 30 pS. The steady-state open probability was voltage-dependent and declined from 0.9 to 0.5 between -80 and -150 mV. Overall, mature OLGs in situ possess time- and also voltage-dependent K+ currents, which may facilitate clearance of K+ released during axonal firing.

The electrical transport across a biomimetic interface made up of spin coated melanin layers on nanotextured silicon surfaces with different texturing features and wetting properties is discussed. Nanotexturing allows, under certain conditions, the melanin to anchor better on a hydrophobic silicon surface, overcoming the hydrophilic melanin–hydrophobic silicon interface issue. The feature of the electrical signal transduction across such a structure was studied by impedance spectroscopy and found to be influenced by the nano-texturing chemistry and surface morphology. The effects of a voltage pulse, as external stimulus modifying the electrical transport mechanisms, and retention of the subsequently achieved carrier transport conditions have been elucidated. The results suggest a possible exploiting of this circuit element for bio and environmental molecules’ sensing.

A novel electrochemical process for the formation of solar selective absorber layers on aluminum is presented. The growth of an alumina layer and the incorporation of metal ions into the layer is done by a one-step procedure using only one electrolytic bath and application of a voltage pulse technique. The influence of selected electrical parameters on the solar selective properties is described and the enhanced stability of an absorber layer, attained by a sol-gel-posttreatment, is discussed. [S0199-6231(00)00602-X]

The results of a study of the effect of the front edge duration of a voltage pulse (τ) on the electric breakdown of ammonium perchlorate single crystals are submitted. Experiments have shown that at τ 1.5 µs. It is shown that the electric breakdown of ammonium perchlorate results from an impact generation of electrons. The impact generation rate of electrons versus electric field and the diameter of the through channel being formed during electric breakdown in ammonium perchlorate are estimated.

Under high current density, lots of organic electroluminescent devices (OELDs) exhibit a substantial decrease in an external quantum coefficient (ηext). Understanding the operating principles of the device is necessary to control the ηext roll off and achieve good performance of OELDs. In this study, we mainly discuss the possible dynamics of charge carrier in our device according to the transient behaviors of electroluminescence (EL) and current after voltage pulse was turn off. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have studied and compared oscillograms of the brightness and the reactive current during the excitation of Al-ZnS:Mn-InxOy structures by a single voltage pulse. Disagreement of the results obtained with solutions of the kinetic equations which describe direct collisional excitation of the activator by hot electrons was observed. Based on the results found and analysis of data in the literature it is proposed that there are excitations which transmit the energy to the manganese centers.

The STM is used as a tool for nanostructure formation by applying a high voltage pulse. Usually these nanostructures are explained in terms of field ion evaporation, which is shown to be questionable. For the Au-Au system a new model is suggested on the basis of local melting of the tip by the Nottingham effect.

On an Au(111) surface, Au atomic diffusion induced by a voltage pulse was demonstrated using a scanning tunneling microscope (STM) with an Au tip in air. Applying a voltage pulse as a trigger, we observed local diffusion of Au atoms around the position where the voltage pulse was applied. Upon repeating tip scanning, fingerlike stripes grew gradually from a step; the direction of the stripes was affected by the structure of the Au(111) surface and the tip-scan direction. In our experiments, movable Au atoms on the local area were swept by tip scanning via the field gradient effect. Local atomic Au diffusion could be induced since activation energy was reduced by applying the voltage pulse.

Controlling streamer morphology is important for numerous applications. Up to now, the effect of the voltage rise rate was only studied across a wide range. Here we show that even slight variations in the voltage rise can have significant effects. We have studied positive streamer discharges in a 16 cm point-plane gap in high-purity nitrogen 6.0, created by 25 kV pulses with a duration of 130 ns. The voltage rise varies by a rise rate from 1.9 kV/ns to 2.7 kV/ns and by the first peak voltage of 22 to 28 kV. A structural link is found between smaller discharges with a larger inception cloud caused by a faster rising voltage. This relation is explained by the greater stability of the inception cloud due to a faster voltage rise, causing a delay in the destabilisation. Time-resolved measurements show that the inception cloud propagates slower than an earlier destabilised, more filamentary discharge. This explains that the discharge with a faster rising voltage pulse ends up to be shorter. Furthermore, the effect of remaining background ionisation in a pulse sequence has been studied, showing that channel thickness and branching rate are locally affected, depending on the covered volume of the previous discharge., Comment: 16 pages, 9 figures

The effect of a high-voltage pulse discharge on the crystal lattice and the surface of quartz grains is studied for different values of the energy input into the interelectrode space, the pulse duration, and the energy input rate. The reasons for the processes of activation of the quartz grain surface and the modification of the crystal lattice of quartz are accounted for. Practical recommendations are issued.

Methods to manipulate single Si atoms on the Si(111)7 × 7 surface at room temperature, using a scanning tunneling microscope (STM) operated in ultrahigh vacuum, are reported. The extraction and redeposition of single Si atoms and the displacement of the redeposited Si atoms can be done with a W tip, if the tip is carefully cleaned, by applying a voltage pulse between tip and sample with its polarity, magnitude and duration being selected appropriately.

The human ether-a-go-go-related gene (hERG) channel is important for repolarization in human myocardium and is a common target for drugs that prolong the QT interval. We studied the effects of two antipsychotics, tiapride and sulpiride, on hERG channels expressed in Xenopus oocytes and also on delayed rectifier K(+) currents in guinea pig cardiomyocytes. Neither the amplitude of the hERG outward currents measured at the end of the voltage pulse, nor the amplitude of hERG tail currents, showed any concentration-dependent changes with either tiapride or sulpiride (3~300 µM). However, our findings did show that tiapride increased the potential for half-maximal activation (V(1/2)) of HERG at 10~300 µM, whereas sulpiride increased the maximum conductance (G(max)) at 3, 10 and 100 µM. In guinea pig ventricular myocytes, bath applications of 100 and 500 µM tiapride at 36℃ blocked rapidly activating delayed rectifier K(+) current (I(Kr)) by 40.3% and 70.0%, respectively. Also, sulpiride at 100 and 500 µM blocked I(Kr) by 38.9% and 76.5%, respectively. However, neither tiapride nor sulpiride significantly affected the slowly activating delayed rectifier K(+) current (I(Ks)) at the same concentrations. Our findings suggest that the concentrations of the antipsychotics required to evoke a 50% inhibition of I(Kr) are well above the reported therapeutic plasma concentrations of free and total compound.

In switching charge-density-wave (CDW) conductors, a voltage pulse greater than threshold causes the CDW to slide only after a delay \ensuremath{\tau}. For identical experimental conditions, we have found a class of delays as long as 5 s with fluctuations as large as 5 orders of magnitude. For large \ensuremath{\tau}, the distribution of delays N(\ensuremath{\tau})\ensuremath{\propto}${\mathrm{\ensuremath{\tau}}}^{\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$, with 0.81.3. We argue that \ensuremath{\tau} measures the time at which the internal strain somewhere in the CDW exceeds the threshold for phase slippage. The electronic history of the sample, and hence the distribution of initial configurations of the CDW, determines N(\ensuremath{\tau}).

The kinetics of voltage-clamped sodium currents were studied in frog skeletal muscle. Sodium currents in frog skeletal muscle activate and inactivate following an initial delay in response to a depolarizing voltage pulse. Inactivation occurs via a double exponential decay exhibiting fast and slow components for virtually all depolarizing pulses used.

We report the electroluminescent characteristics of organic multilayer light‐emitting diodes (LEDs) with a benzophenone (BP) dispersed poly(methylmethacrylate) (PMMA) film as an emitting layer. The electroluminescence (EL) intensity of these LEDs increases with decreasing temperature from 273 to 100 K when they are operated at the same voltages or the same current densities. The EL spectrum of the LEDs, which peaks at around 450 nm, is identical to the phosphorescence spectrum of BP in PMMA. In addition, the EL decay time was determined as 46.8 μs at 100 K by applying a rectangular voltage pulse. These results indicate that the EL of the LED originates from the triplet excited states of BP.

Surface discharge velocity measurements are reported. An aluminium strip fixed on the underside of a polyester film trapped corona charge on the surface and guided the discharge initiated by a 100 ns voltage pulse of between 10 to 30 kV. The surface charge was of opposite polarity to the voltage pulse. Results for the discharge velocity under various conditions are presented and indicate that both surface charge and the voltage pulse are responsible for driving the discharge across the length of the polyester.

A simple experimental technique for measuring the sheath length in a low-pressure glow discharge has recently been proposed in which the sheath length is determined from measurement of the transient current resulting from a rapidly rising voltage pulse applied to a steady-state discharge. In this comment, the sheath length deduced from a simulation of this experimental technique is compared with the sheath length determined directly from self-consistent calculations of the electric field profile. The excellent agreement found between these two calculations of the sheath length provides validation of the experimental technique.

Measurements of the voltage-pulse-induced time-domain depolarization (VPITDD) were used to investigate plasma polymerized organosilicon films. It was found that the observed relaxations were related to bulk processes. A two-center model was proposed to describe this phenomenon. Poole-Frenkel centers and traps lying near the Poole-Frenkel energy level were attributed to the observed relaxations. >

In this study, a durable sensor device for blood cell counter has been developed using MEMS technology. The number of blood cells in human blood can be counted and checked with 10 mm × 5 mm silicon MEMS device. Aperture-impedance method was used to detect blood cells as voltage signals. As a result of investigations, suitable materials for the electrode of the device have been found. First, latex particles were used to confirm the operation of the blood cell counter instead of blood and finaly actual blood was measured. The size difference of latex particles and concentration of latex particles were successfully recognized from the height of voltage pulse and the number of pulses, respectively.

Development of economical and efficient methods to eliminate SO2 and NOx is strongly needed, although a combined technology of selective catalytic reduction of NOx by ammonia and neutralization of SO2 by Ca(OH)2 is currently used. New regulations have set limits for SO2/NOx emission and opened up a large market for technologies that can control emissions.

Light-emitting devices based on Langmuir-Blodgett films of a porphyrin derivative have been fabricated. In transient electroluminescence (EL) studies, we have observed two components: an instantaneous part and a peak part consisting of a linear rise followed by an exponential decay to a constant level. The time evolution of EL has been explained in terms of intrinsically accumulated charges and hole-induced electric field redistribution. This field redistribution has further been studied by integral mode time-of-flight technique during and after the application of voltage pulse.

We have observed a switching transition between bistable memory switching and monostable threshold switching in Pt/NiO/Pt structure. Bistable memory switching could be changed to monostable threshold switching by applying a positive electrical pulse with height of 2 V and width between 10−2 and 10−4 s. The change is reversible by applying a negative electrical pulse with the same height and width. By considering polarity- and width-dependence of the switching transition and compositional difference on electrical properties in NiOx, we have proposed a model in which the migration of oxygen ions (O2−) is responsible for the switching transition in Pt/NiO/Pt structures.

We report a memory effect in electroluminescence of Er-doped silicon light emitting diodes: applying a voltage pulse in reverse-bias direction below breakdown we observe 1.54μm emission only, if a forward pulse was issued before. This effect occurs for temperatures T⩽120K in sublimation molecular-beam epitaxy grown structures. This finding opens perspectives for the development of a fully complementary metal-oxide-semiconductor compatible electro-optical converter with a memory function, operating in the 1.5μm telecommunication band. Such an element could find numerous applications in telecommunication and silicon photonics and optoelectronics circuitry.

A self-synchronized voltage pulse application method was demonstrated as an effective control of the nano-oxidation using a dynamic force microscope. By creating a cyclic water meniscus using the large oscillation amplitude, self-synchronized voltage pulses can be realized during application of a continuous voltage to the sample. The modification of the probe-sample distance was equal to the change in the applied voltage pulse duration on the order of submicroseconds. This method realized the ultrastable control of the water meniscus formation.

The charge-pumping current results from recombination associated with the SiO2Si interface traps under the gate of a MOSFET when a voltage pulse is applied to the gate. A model is proposed which predicts this current as a function of the frequency, amplitude, and average voltage of pulses with peak-to-peak amplitudes less than the difference between the flatband and inversion voltages and with pulse transistions fast enough so that negligible capture or emission occurs during the transition. The model is based on Shockley-Read-Hall traps segregated by energy and capture cross section into traps which capture only and traps which tend to emit before capture. It predicts the dominant behavior of the measured current and with the inclusion of surface potential fluctuations and a distribution of cross sections it agrees well with experiment. Thus, the charge-pumping current due to these small rectangular pulses can be used to determine the density, the electron capture cross section, and the hole capture cross section of interface traps near midgap.

Data are obtained on the lag time of the breakdown and the dielectric strength of a solid porous dielectric with a porosity of 0.4 (pressed lead azide) with different durations of a rectangular voltage pulse from 10−8 to 2 · 10−6 sec.

An electrochemical reactivation method for solid electrodes used in electrochemical detectors is optimized for glassy carbon electrodes. Application of a voltage pulse train for 5 min is effective in restoring the response of the electrode after deactivation by organic compounds. Potassium hexacyanoferrate(II) and dl -synephrine were used to test the reactivation of electrodes; 2,6-dihydroxybenzoic acid and urine served to deactivate them. The effects of the amplitude, d.c. level, and frequency of the applied voltage pulse train, as well as the mode of termination, are discussed.

Thin amorphous films of chalcogenide Te 48 As 18 Ge 6 Si 28 were prepared and their current-voltage (I–V) characteristics were examined. Memory switching effects were observed which were stable and reproducible, but the switching voltage was found to depend on the restoring voltage in a regular way for cyclic switching. Furthermore, the time delay for an applied voltage pulse to cause switching may be related to the I–V curve prior the switching. This dependence seems to support an electronic mechanism of switching.

The charge versus centroid relationship is determined by staircase charging, in which a sequence of identical pulses is applied, the memory device is returned to flat-band condition after each pulse, and the subsequent pulse is superimposed on the flat-band voltage corresponding to the accumulated memory charge distribution resulting from the preceding pulses. Staircase patterns of accumulated negative charge and of device voltage are analyzed, and effects arising from back-tunneling and leakage currents are identified. Comparison of the initial injection current during a voltage pulse with the steady-state current indicates that hole injection from the gate does not contribute significantly to the steady-state oxide tunnel current.

Threshold switching was observed under voltage pulse excitation in thin (2000– 8200 A) polymer films. For a given applied voltage V (greater than the threshold) the sequence of switching events stops after a given time; new switchings are possible if the applied voltage is increased. Data on the statistical distribution of the number of events in a given switching sequence versus applied voltage amplitude suggest the existence of two independent gaussian phenomena. We assume these to be related to weak spots and to true bulk phenomena of the films during switching.

The radiation rise and the spacetime characteristics of the IR radiation from acoustoelectric domains are investigated. It is found that the IR radiation emitted from moving and stationary domains rises under nonstationary conditions for the ultrasonic flux in the domains. For the moving domain such conditions onset when it comes up to the regions of the nonuniform electric field in the sample. For the stationary domain nonstationary conditions appear as a result of the arrival of the shock ultrasonic wave packets to the domain. This packet is generated in the regions of the electric field gradient in the sample when the voltage pulse is applied. It is found by the electron-optical chronography method that in some cases under nonstationary conditions for the moving domain a system of rapidly moving light spots appears, which may be interpreted as Gunn domains. The mechanism of IR light emission rise is discussed. Der Strahlugsanstieg und die RaumZeit-Charakteristiken der IR-Strahlung von akustoelektrischen Domanen werden untersucht. Es wird gefunden, das die von den wandernden und stationaren Domanen emittierte IR-Strahlung unter nichtstationaren Bedingungen fur den Ultraschallflus in den Domanen anwachst. Fur die wandernde Domane setzt diese Bedingung ein, wenn sie in Bereiche eines nichtgleichformigen elektrischen Feldes der Probe gelangt. Fur die stationare Domane treten nichtstationare Bedingungen als Ergebnis der Ankunft des Ultraschallstoswellenpakets an der Domane ein. Dieses Paket wird in den Bereichen eines elektrischen Feldgradienten in der Probe erzeugt, wenn der Spannungsimpuls angelegt wird. Es wird mit der elektronenoptischen chronographischen Methode gefunden, das in einigen Fallen unter nichtstationaren Bedingungen fur wandernde Domanen ein System von schnell wandernden Lichtpunkten auftritt, das als Gunn-Domanen interpretiert werden kann. Der Mechanismus der IR-Emissionsanstiegs wird diskutiert.

New results are presented on the analysis of silicon surfaces in a Time-of-Flight Atom Probe. Comparison is made between the chemical data obtained from conventional voltage pulse and laser pulse desorption.

The results are presented of investigations of new cerment discharge gaps, having operating voltages of 9?7 and 20?16 kV and filled with various gas mixtures (argon and nitrogen, pure nitrogen). The dependences are given of the delays in firing the gaps, as a function of the voltage on the electrodes and of the energy of the laser pulses used for triggering (? = 1.06 ?). The minimum triggering energy of the type 1 discharge gaps was 2 ?J, when using a radiation pulse having ?rad = 70 nsec. The rise time of the voltage pulse produced was 0.5 nsec. The discharge gaps were used to control electrooptic switches in laser systems. A study was made of the radiation produced during the breakdown of the discharge gaps. The radiation pulse had a flat top and a rise time of ? 1.5 nsec.

A scanning tunneling microscope has been used to observe the behaviour of adsorbates on an annealed gold surface. We show, by means of time lapse sequences, that weakly bound adsorbates can be loosened or removed simply by the action of taking a normal scan. Their redeposition after a short period of time is also demonstrated. In addition, we show that more strongly bound species together with larger masses of adsorbates may be removed by applying a voltage pulse to the tip.

A wall-stabilised argon arc (35 A) submitted to recurring decay and reignition is disturbed during its decay phase by a high-voltage peak which includes some electrical parameter variations. The spectral observation of this event is presented. This study shows that the arc conductance variation for a short voltage pulse arises from electron heating.

In most work dealing with space‐charge‐limited currents, the diffusive contribution to the current is neglected. The classic steady‐state problem was handled by Mott and Gurney. For their problem of the perfect insulator it is well known that diffusion dominates near the injecting contact but, after some critical distance, drift dominates, and it is consistent to neglect diffusion.For the case of transient SCLC the mathematical validity of neglecting diffusion has not been shown. The purpose of this work is to show that for times greater than a critical time and distances greater than a critical distance the diffusive term can consistently be neglected. The solutions found by Mark and Helfrich and by Many and Rakavy for injection of electrons into an insulator under an applied voltage pulse have been shown to be correct under the above conditions. The interesting result is that the critical parameters are related to geometrical parameters by the ratio of the thermal voltage kT/q to the applied voltage. We therefore find that for signals large compared to kT/q, the neglect of diffusion is valid over most of the range of time and distance associated with the problem.

In a point‐to‐plane gap in atmospheric air streamers propagate under a voltage pulse from the point anode into the low‐field region at high velocities and under continuous branching. It was found that electron emission from the copper cathode occurs under the effect of the high field between the streamer tips and the cathode just before impact. Photographic evidence by means of paper films placed on the cathode with sensitive emulsion facing it showed that at the points where strong streamer tips approached the back side of the film great concentrations of minute dots appeared. These dots are attributed to electron avalanches produced by those electrons liberated from the cathode and accelerated towards the streamer tip. The liberation of electrons was ascribed to the high field intensities at the tips since radiation cannot penetrate the paper. To confirm this, the back side of the paper was blackened at spots with no change in pictures. To further substantiate this, a thin metallic layer was placed at t...

Investigations of current oscillations observed in high resistivity Au-compensated n+–i–in+ and p+–p+ silicon samples are reported. The specific resistivities of the i regions are 20 k Ω cm and about 105 Ωcm at the n-type Si and 14 k Ωcm at the p-type silicon, respectively. The dc I–U-characteristics and the contact preparation justify the assumption that single injection SCLC are attributable to the current oscillations and that double injection is negligible. The waveforms of the oscillations are not sinusoidal in general. The frequencies are in the range of 100 kHz at the 105 Ωcm material. In the 20 k Ω cm samples a pulse like waveform is typical for the current instabilities and the repetition rate of the pulses is about 10 kHz. Measurements using voltage pulses show that current oscillations are initiated a certain delay time after applying the voltage pulse, if a critical trap occupation is reached. Es wurden Stromoszillationen in hochohmigen Au-kompensierten n+–i–n+- und p+–i–p+-Siliziumproben untersucht. Die spezifischen Widerstande der i-Zone betrugen 20 k Ω cm und ca. 105 Ωcm bei dem n- und 14 k Ω cm bei dem p-Material. Die dc I–U-Kennlinien und die Kontaktherstellung lassen darauf schliesen, das der Ladungstransport durch Majoritatstragerinjection geschieht und das Doppelinjektion vernachlassigbar ist. Der zeitliche Verlauf des Stromes ist im allgemeinen nicht sinusformig. Die Wiederholfrequenzen liegen bei dem ca. 105 Ωcm-Material im 100 kHz-Bereich. Bei den 20 k Ω cm-Proben tritt ein impulsformiger Stromverlauf mit einer Wiederholfrequenz von ca. 10 kHz auf. Messungen mit Spannungsimpulsen zeigen, das die Oszillationen eine bestimmte Zeit zum Anschwingen benotigen und das eine kritische Trapbesetzung fur ihr Auftreten Voraussetzung ist.

Potentiostatic voltage-pulse experiments, carried out on anodically formed tantalum oxide films, show directly the existence of a dielectric polarization process which is driven by the passage of ion-current. Furthermore, quantitative analysis of the data yields a value for the constant coupling the polarization rate to the ion-current density, of the same order as that obtained from galvanostatic field transients, a result expected if the dielectric polarization of the film makes a large contribution to the effective field causing film growth. This experiment provides, therefore, convincing evidence in support of the main tenet of the dielectric polarization theory for anodic film growth (the ion-current-driven polarization process) with some support for the effective-field postulate also provided.