Electron emission from ferroelectrics (FEE) is an unconventional electron emission effect. Methods of FEE excitation are quite different compared to classic electron emission from solids. Two kinds of FEE have been observed, “weak” and “strong.” “Weak” electron emission (current density 10−12–10−7 A/cm2) occurs from polar surfaces of ferroelectric materials in the ferroelectric phase only. A source of the electric field for “weak” FEE excitation is an uncompensated charge, generated by a deviation of macroscopic spontaneous polarization from its equilibrium state under a pyroelectric effect, piezoelectric effect, or polarization switching. The FEE is a tunneling emission current which screens uncompensated polarization charges. It is shown that the FEE is an effective tool for direct domain imaging and studies of electronic properties of ferroelectrics. “Strong” FEE, which is 10–12 orders of magnitude higher than “weak” FEE, achieves 100 A/cm2 and is plasma-assisted electron emission. Two modes of the sur...

Electron emission from ferroelectrics

The invention relates to a method of separating components of a fluid mixture comprising the steps of providing a fluid, providing a sorbent structure (120), sorbing a first component of the fluid, desorbing the first component, and electrokinetically biasing the first component in a direction other than the vector of the fluid mixture.

Sorption method, device, and system

Spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a nonpolar state or vice versa If spontaneous polarization changes are induced at a submicrosecond time scale, strong uncompensated surface charge densities and related fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric cathode The nature of this self-emission differs essentially from other methods of ferroelectric electron emission and from conventional electron emission in that the latter methods are only achieved by extracting electrons with externally applied electric fields When electron guns are constructed with ferroelectric cathodes, new design criteria have to be taken into account The intensity, the energy, the temporal and spatial distribution and the repetition rate of the emitted electron beams can be adjusted within wide limits The advantages of fer

http://cds.cern.ch/record/376764/files/lhc-98-006.pdf

Features and technology of ferroelectric electron emission

A dielectric barrier plasma discharge device consistent with certain embodiments of the present invention has a pair of electrodes spaced apart by an electrode gap. A dielectric is disposed between the electrodes. The electrode gap is provided with a gas at a specified pressure. A rapid rise time voltage pulse generator produces a voltage pulse across the electrodes to cause an extreme overvoltage condition, wherein the rapid rise time is less than a plasma generation time so that the extreme overvoltage condition occurs prior to current flow across the electrode gap. Due to the high voltages and high current densities, the product yields an extremely high instantaneous power density. This extreme overvoltage condition is also believed to lead to production of shock waves and runaway free electrons. The resulting plasma can be utilized to carry out many potential tasks including, but not limited to etching, deposition, and sterilization. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.

Pulsed dielectric barrier discharge

Results of spectroscopic investigations of the plasma formed on the surface of a ferroelectric cathode upon the application of a driving pulse are presented. The ferroelectric plasma cathode was made of a solid solution of Sr, Ba, Ti, Nb, Pb, and O. Its front side was covered by Cu grounded strip electrodes. A driving pulse with an amplitude ≲18 kV and pulse duration of ∼400 ns was applied to the rear Cu disk electrode. A Jobin-Yvon 750M spectrometer was used for visible light dispersion. Spectral line profiles were obtained by a fast framing camera. It was shown that light is emitted from the excited ions and neutral atoms of Cu, Pb, Sr, Ba, Ti, and H within the first 50 ns after the beginning of the driving pulse. By analyzing the Doppler broadening of the observed spectral line profiles it was found that the ion and neutral atom temperature is ⩽0.8 eV. Analysis of the Stark broadening of the Hα and Hβ spectral lines showed the absence of a high (>1 kV/cm) electric field which could be developed at the ...

/pdf/spectroscopy-of-a-ferroelectric-plasma-cathode-579fu3vjrq.pdf

Spectroscopy of a ferroelectric plasma cathode

It is shown that nonprepoled PLZT ceramics, both in ferroelectric and antiferroelectric phase, emit intense current bursts when a negative exciting voltage is applied to the rear surface of the cathode. The spontaneous polarization induced in the bulk by applying the field through the cathode disk, creates a sheet of negative charge on the diode boundary of the ferroelectric. This, in turn, induces such a high electric field at the diode dielectric surface that electrons are ejected out from the ceramic surface into the vacuum. The coherent behaviour of the displacement and emitted current shows clearly that the emission is due to a variation of spontaneous polarization. A second effect generated by the application of the high voltage pulse at the rear side is the formation of a surface plasma. Applying a positive voltage to the anode, electrons are readily transferred through the diode gap.

/pdf/displacement-and-emission-currents-from-plzt-8-65-35-and-4-bwhd0fq1xs.pdf

Displacement and emission currents from PLZT 8/65/35 and 4/95/5 excited by a negative voltage pulse at the rear electrode

With increasing rf power, the electron concentration in the plasma of electron cyclotron resonance (ECR) ion sources is decreasing in comparison to the ion concentration, so that the plasma is charging up positively. When reviewing the basic performance requirements of ECR sources it becomes evident that the direct injection of electrons into the ECR plasma is increasing the electron charge density and the ion current yield. Ferroelectric ceramics was used as very robust, electron emitting cathode material under the heavy-duty conditions inside the plasma chamber of an ECR ion source. The electron emission from the ferroelectric cathode is turned on by a high repetition-rate bipolar pulse of ±1.2 to 1.6 kV amplitude to the electrodes deposited on both sides of the disk-shaped cathode. Lead–barium–zirconium-titanate (30/70/30) cathodes doped with 2 mol % Bi2O3 were installed and tested in the Ar–ion plasma of the ECR ion source CAESAR at INFN-LNS, Catania. The aim was to visibly increase the yield of the i...

Ion source improvement by electron injection from a ferroelectric cathode

With increasing RF power the electron concentration in the plasma of ECR ion sources is decreasing in comparison to the ion concentration, so that the plasma is charging up positively. Direct injection of electrons into the ECR plasma can increase the electron charge density and the ion current yield. We have used ferroelectric cathodes to inject electrons into the Argon plasma of the CAESAR ion source at INFN-LNS (Catania, Italy). The cathode was placed at about 10 cm from the hot plasma and a bipolar high voltage pulse of 1.6 kV was used to trigger the electron emission. No additional acceleration has been provided. The use of the ferroelectric cathode leads to an increase of about 30% of the Ar 8+ intensity, which has been monitored during the test. In addition, magneto-hydrodynamic instabilities in the ECR source were damped during and after electron injection.

/pdf/application-of-ferroelectric-cathodes-to-enhance-the-ion-37m0cgnyss.pdf

Application of Ferroelectric Cathodes to Enhance the Ion Yield in the Caesar Source at LNS

With increasing RF power the electron concentration in the plasma of ECR ion sources is decreasing in comparison to the ion concentration, so that the plasma is charging up positively. Direct injection of electrons into the ECR plasma can increase the electron charge density and the ion current yield. We have used ferroelectric cathodes to inject electrons into the Argon plasma of the CAESAR ion source at INFN-LNS (Catania, Italy). The cathode was placed at about 10 cm from the hot plasma and a bipolar high voltage pulse of 1.6 kV was used to trigger the electron emission. No additional acceleration has been provided. The use of the ferroelectric cathode leads to an increase of about 30% of the Ar intensity, which has been monitored during the test. In addition, magneto-hydrodynamic instabilities in the ECR source were damped during and after electron injection.

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH Laboratory for Particle Physics APPLICATION OF FERROELECTRIC CATHODES TO ENHANCE THE ION YIELD IN THE CAESAR SOURCE AT LNS

The emission of electrons from lead lanthanum zirconate titanate ceramics, showing ferroelectric or/and antiferroelectric properties at room temperature, after excitation by a rectangular high voltage electric pulse, is explained by the switching and relax-back of the spontaneous polarization. The reported simultaneous measurements of emitted and polarization switching pulses show clearly the expected correlation. From the shape of the switching current it is possible to foresee if the sample can emit or not.

Correlation between emitted and polarization current in ferroelectric lead lanthanum zirconate titanate ceramics

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