Effect Of Strong Electric Field Research Articles

Effect of a strong electric field on a nematogen: evidence for polar short range order

We present experimental studies on the effect of strong electric fields on the nematogen p-cyanophenyl p-n-heptyl benzoate which has the strongly polar cyano end group and a large positive dielectric anisotropy. We use a local temperature measurement to take into account heating effects and an electrical impedance analysis to determine both the dielectric constant (e∥) and the resistance (R) of the sample. We also measure the higher harmonic responses of the medium. The new results obtained in this study are: (i) a detailed temperature dependence of the terms which describe (a) the quenching of macroscopic thermal fluctuations of the nematic director and (b) the enhancement of the orientational order parameter due to Kerr effect, (ii) clear evidence for the critical divergence of susceptibility as reflected in the third harmonic signal, (iii) an unusual enhancement of the conductivity which shows a large peak just below the critical point Tc, (iv) a significant peak in the second harmonic signal at Tc and (v) evidence for a field induced nematic-nematic transition well inside the nematic range. We argue that the results (iii)-(v) indicate the presence of polar short range order in the medium and hence support a molecular model in which such an order has been proposed.

Studies of field related effects in the fabrication process on graphite using a scanning tunneling microscope

The surface modification process with low energy electron beams, generated with a scanning tunneling microscope, is investigated using graphite as an example. By analyzing the cross-sectional profiles, it is shown that local transport properties could play a vital role in determining the characteristics of the fabricated craters. In addition, the observed asymmetry in the contours of the as-produced craters is proposed to be correlated with the geometry of the tip apex region. It is therefore suggested that one look into the roles of low energy electrons, together with the effects of strong electric field, in the fabrication process.

Strong electric-field effects on the doubly-excited intrashell states of He below the He + ( N =2) threshold

The method of complex-coordinate rotation is used to investigate electric-field effects on the doubly-excited 2s2p1P0, 2p21De, 2p23Pe and 2s2p3P0 states of He. Strong electric-field strengths up to F = 0.02 Ry are used in our present study. Products of Slater orbitals are used to represent the two-electron wave functions, with lmax = 8 being employed for the individual electron. Block matrices with up to Lmax = 5 (H-states) are used to investigate the convergence behavior for the resonance parameters (resonance energy and width). When the external electric field is turned on, “classic” Stark effect is observed for the M = 0 and M = ±1 components of the two singlet-spin states and for the M = ±1 components of the triplet-spin states. Comparisons are made with other calculations when available.

Bloch oscillations

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Kurz Heinrich , Roskos Hartmut G. , Dekorsy Thomas and Klaus Köhler 1996Bloch oscillationsPhil. Trans. R. Soc. A.3542295–2310http://doi.org/10.1098/rsta.1996.0101SectionRestricted accessArticleBloch oscillations Heinrich Kurz Google Scholar Find this author on PubMed Search for more papers by this author , Hartmut G. Roskos Google Scholar Find this author on PubMed Search for more papers by this author , Thomas Dekorsy Google Scholar Find this author on PubMed Search for more papers by this author and Köhler Klaus Google Scholar Find this author on PubMed Search for more papers by this author Heinrich Kurz Google Scholar Find this author on PubMed Search for more papers by this author , Hartmut G. Roskos Google Scholar Find this author on PubMed Search for more papers by this author , Thomas Dekorsy Google Scholar Find this author on PubMed Search for more papers by this author and Köhler Klaus Google Scholar Find this author on PubMed Search for more papers by this author Published:15 October 1996https://doi.org/10.1098/rsta.1996.0101AbstractThe status quo of the research on Bloch oscillations in semiconductor superlattices is outlined. Bloch oscillations excited by femtosecond laser pulses have been investigated by different optical techniques. They have allowed measurement of the internal electric field changes associated with the charge oscillations, the emitted terahertz electromagnetic radiation and the nonlinear coherent optical response, all directly in the time domain. The main results are summarized and critically reviewed. The potential of Bloch oscillations for practical applications in terahertz radiation sources is assessed.FootnotesThis text was harvested from a scanned image of the original document using optical character recognition (OCR) software. As such, it may contain errors. Please contact the Royal Society if you find an error you would like to see corrected. Mathematical notations produced through Infty OCR. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Islam Q, Meng F, Thomson M and Roskos H (2020) Terahertz photoconductive waveguide emitter with excitation by a tilted optical pulse front, Optics Express, 10.1364/OE.403161, 28:22, (33673), Online publication date: 26-Oct-2020. Gruzdev V and Sergaeva O (2018) Ultrafast modification of band structure of wide-band-gap solids by ultrashort pulses of laser-driven electron oscillations, Physical Review B, 10.1103/PhysRevB.98.115202, 98:11 Vakhnenko O (2016) Coupling-governed metamorphoses of the integrable nonlinear Schrödinger system on a triangular-lattice ribbon, Physics Letters A, 10.1016/j.physleta.2016.04.034, 380:24, (2069-2074), Online publication date: 1-May-2016. Muniz C and Cunha M (2015) Effects of strong electric fields in a polyacetylene chain, Journal of Physics and Chemistry of Solids, 10.1016/j.jpcs.2015.02.009, 82, (17-20), Online publication date: 1-Jul-2015. Sokolov V and Iafrate G (2012) Spontaneous Emission of Bloch Oscillation Radiation in the Terahertz Regime Handbook of Nanoscience, Engineering, and Technology, Third Edition, 10.1201/b11930-9, (67-124), Online publication date: 15-Jun-2012. Belotelov V, Bykov D, Doskolovich L and Zvezdin A (2010) On surface plasmon polariton wavepacket dynamics in metal–dielectric heterostructures, Journal of Physics: Condensed Matter, 10.1088/0953-8984/22/39/395301, 22:39, (395301), Online publication date: 6-Oct-2010. Hummel A, Bauer T, Mohler E and Roskos H (2006) The coherent Hall effect of charge carriers in a superlattice: semiclassical description of the wavepacket dynamics, Journal of Physics: Condensed Matter, 10.1088/0953-8984/18/8/013, 18:8, (2487-2509), Online publication date: 1-Mar-2006. Axt V and Kuhn T (2004) Femtosecond spectroscopy in semiconductors: a key to coherences, correlations and quantum kinetics, Reports on Progress in Physics, 10.1088/0034-4885/67/4/R01, 67:4, (433-512), Online publication date: 1-Apr-2004. Gaidis M, Lee K, Samoska L and Wyss R Frequency-controlled sources of far-infrared radiation for spaceborne applications 2000 IEEE/EIA International Frequency Control Symposium and Exhibition, 10.1109/FREQ.2000.887419, 0-7803-5838-4, (565-577) Kempa K, Bakshi P, Du C, Feng G, Scorupsky A, Strasser G, Rauch C, Unterrainer K and Gornik E (1999) Towards stimulated generation of coherent plasmons in nanostructures, Journal of Applied Physics, 10.1063/1.369736, 85:7, (3708-3712), Online publication date: 1-Apr-1999. Wolter F, Martini R, Tolk S, Haring Bolivar P, Kurz H, Hey R and Grahn H (1999) Influence of carrier–carrier scattering on intraband dephasing, Superlattices and Microstructures, 10.1006/spmi.1999.0763, 26:2, (93-102), Online publication date: 1-Aug-1999. Shah J (1999) Recent Developments Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures, 10.1007/978-3-662-03770-6_9, (325-446), . Luban M and Luscombe J (1998) Dynamical localization of electrons in an aperiodic superlattice, Physical Review B, 10.1103/PhysRevB.57.9043, 57:15, (9043-9049) Chamberlain J, Miles R, Collins C and Steenson D (1997) Introduction to Terahertz Solid-State Devices New Directions in Terahertz Technology, 10.1007/978-94-011-5760-5_1, (3-27), . Cho G, Ziebell A, Dekorsy T, Bakker H, Opitz U, Kohl A and Kurz H (1997) Electroabsorption Dynamics in an InGaAsP/InGaAsP Superlattice Modulator Ultrafast Electronics and Optoelectronics, 10.1364/UEO.1997.UG5, 1-55752-486-6, (UG5) This Issue15 October 1996Volume 354Issue 1717 Article InformationDOI:https://doi.org/10.1098/rsta.1996.0101Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online01/01/1997Published in print15/10/1996 License:Scanned images copyright © 2017, Royal Society Citations and impact

Effect of Strong Electric Fields on Phase Transitions in Some Liquid Crystals

An electric field couples to the orientational order in liquid crystals through dielectric anisotropy and is conjugate to the order. However the ionic flow produced by the field causes a dissipatio...

The Effect of Strong Electric Field on Microhardness and Mobility of the Indented Dislocations in Alkali Halides

Abstract Some regularities and particular specialties of electromechanical effect have been investigated in NaCI single crystals. The conclusion has been drawn that the existence of the electromechanical effect in crystals with ionic interatomic bonds appears to result from both the direct electrical field's force on charged dislocations, as the filaments and the modification under field influence the impurities, and point defect's state in the crystal lattice. The last modification is to vary the interactions between the obstacles and the dislocations moving in solid, thus facilitating or hardening the microplastic deformation in the hole.

Probing and inducing surface chemistry with the STM: the reactions of Si(111)-7 × 7 with H 2O and O 2

We discuss the applications of scanning tunneling microscopy and spectroscopy to both probe and induce surface chemistry with atomic resolution. The reactions of Si(111)-7 × 7 with H 2O and O 2 are considered. In the case of the H 2O reaction, we find a site selectivity consistent with a dominant dissociative chemisorption mechanism. In the case of the oxidation reaction we image two distinct oxygen containing species being formed in the early stages of oxidation. With the help of electronic structure calculations we are able to identify the nature of these species and propose an oxidation mechanism. Through the combined effects of strong electric fields and chemical interactions between the STM tip and individual adsorbates on the H 2O-exposed surface at close range, we are able to remove individual adsorbates and thus restore local reactivity.

Probing and inducing surface chemistry with the STM: the reactions of [formula omitted] with H 2O and O 2

Abstract We discuss the applications of scanning tunneling microscopy and spectroscopy to both probe and induce surface chemistry with atomic resolution. The reactions of Si(111)-7 × 7 with H2O and O2 are considered. In the case of the H2O reaction, we find a site selectivity consistent with a dominant dissociative chemisorption mechanism. In the case of the oxidation reaction we image two distinct oxygen containing species being formed in the early stages of oxidation. With the help of electronic structure calculations we are able to identify the nature of these species and propose an oxidation mechanism. Through the combined effects of strong electric fields and chemical interactions between the STM tip and individual adsorbates on the H2O-exposed surface at close range, we are able to remove individual adsorbates and thus restore local reactivity.

Generalized equations for the steady-state analysis of inhomogeneous semiconductor devices

The generalized equations for the study of the steady-state charge transport in inhomogeneous semiconductor devices are reviewed and extended to take into account the effects of strong electric fields. Inhomogeneous semiconductors are assumed to have the position-dependent band structure which may occur in heterojunctions, graded-bandgap, and nonuniformally doped semiconductors. The generalized equations for the electron and hole current densities are derived by using the exact solution of the Boltzmann transport equation in relaxation time approximation. In semiconductors with parabolic band structure, cubic symmetry and wave-vector-independent relaxation time, these equations reduce to useful form for the modelling of semiconductor devices. The generalized expressions for the electric current densities and nonequilibrium electron and hole densities are expressed in the conventional form used for nondegenerate semiconductors at constant temperature. As a application of these generalized equations a general expression for the photovoltage of solar cell is derived. It is shown that in addition to already known sources of the photovoltage, obtained from the first-order solution of the Boltzmann transport equation, the photovoltage can also arise from the gradients of both the photoelectric field, and the equilibrium densities and mobilities of electrons and holes.

Low temperature specific heat and superconductivity related to microstructure and magnetism of orthorhombic and tetragonal phases Y(1−x)HoxBa2Cu3O(7−δ) (x=0, 0.5 and 1)

Abstract Low temperature specific heat and susceptibility measurements correlated with microstructure determination of Y (1− x ) Ho x Ba 2 Cu 3 O 7−δ in the orthorhombic and the tetragonal phases are described. A strong crystalline electric field effect is observed for both states yielding Schottky anomalies in the specific heat. The tetragonal structure is accompanied by a depression of the magnetic amount of Ho 3+ except for x =0.5 which shows an important Schottky anomaly.

Strong electric field effect on weak localization

The influence of an electric field on weak localization is studied by a recently proposed generalized quantum Langevin equation approach to the conductivity problem. A general formula for the memory function of the non-interacting electron gas, in the presence of high order impurity scattering and an arbitrary electric field, is derived. In the low field case, a scale and frequency dependent conductivity is obtained, which reduces to the well known scale dependent conductivity in the static limit. In the high field case, the conductivity is field dependent through the drift velocity. It is shown that the presence of strong electric fields tends to delocalize the one and two dimensional electron systems if one adopts the electron heating model. However, if the electron gas does not heat up, the conductivity will be field independent.

Rainbows in strong vertical atmospheric electric fields

The effects of strong vertical atmospheric electric fields and electrically charged raindrops on the primary rainbow are considered. A vertical electric field alters the bow by stretching the raindrops vertically. The effects may be visible only for the extremely large electric fields (E > 105 V m−1) sometimes encountered in thunderstorms. The electric field raises and brightens the top of the primary bow but reduces the relative intensity and spacing between the supernumeraries. Electrical charges do not have any visible effect on the rainbow because they significantly increase the ellipticity of only the largest and most highly charged drops, which do not contribute to the bow’s top.

Optical studies on the electric field dependence of excited donor states in silicon

The effect of strong electric fields on some excited states of the substitutional selenium donor in silicon has been investigated with the aid of a new method for determining Fourier transform photoresponse spectra of impurity centers in the depletion regions of diodes. The response concerned is the current in the external circuit of the diode arising from centers in a certain zone, this zone being controlled by trap-filling pulses applied to the diode in synchronism with the movement of the spectrometer’s scanning mirror. The measurements show that the 1s1T2 and 2p0 states of the selenium donor are subject to quadratic Stark shifts of 2.1×10−16 and 3.0×10−15 eV m2 V−2, respectively. Further, thermal emission from these states to the conduction band is found to be enhanced by the field. Finally, it is found that at high fields transitions from the ground state of this neutral double donor to the spin-triplet component 1s3T2 may occur, a fact which has not been directly observed previously.

Capacitive and conductive dynamic response of ion-selective electrodes

Abstract

Developmental studies of Hanford miniature swine exposed to 60-Hz electric fields.

Evaluations of reproductive and developmental toxicology, including teratology, were included as part of a broad screening study in Hanford Miniature swine (HMS) to detect effects of exposure to electric fields. One group (E) was exposed to a uniform, vertical, 60-Hz, 30-kV/m electric field for 20 h/day, 7 days/week; sham-exposed (SE) swine were housed in a separate, environmentally equivalent building. The first generation (F0) gilts were bred after 4 months of study; some were killed for teratologic assays at 100 days of gestation (dg), and the others produced an F1 generation of offspring. The pooled incidence of terata in these litters (teratologic assays and live births) was similar in the E and SE groups. The F0 females, which produced the F1 generation, were bred again after 18 months of exposure and were killed at 100 dg. Malformation incidence in E litters (75%) was significantly greater than in SE litters (29%). No consistent differences in litter size, fetal mass, or mass of fetal organs were detected. The F1 gilts were bred at 18 months of age; defective offspring were found in significantly more of the E litters (71%) than in SE litters (33%). These F1 females were bred again 10 months later and teratologic assays were performed on their second litters at 100 dg. The percentage of litters with malformed fetuses was essentially identical in the E and SE groups (70% and 73%, respectively). There appears to be an association between chronic exposure to a strong electric field and developmental effects in swine, although the change in incidence of malformations between generations and between the first and second breedings makes it impossible to conclude unequivocally that there is a cause-and-effect relation.

Hot carrier recombination in GaAs-GaAlAs quantum wells and superlattices

Abstract We have performed pseudopotential calculations of the electronic structure of GaAs-GaAlAs superlattices which reveal a rich variety of new confined states in the hot carrier energy range. In particular, we find states exhibiting a mixing of momenta from the principal and secondary band minima which leads to significant changes in recombination rates. We have also calculated the effect of strong external electric fields upon the electronic structure. Broad resonances are obtained and the computed resonance widths account for the observed quenching of exciton luminescence.

Measurement of electrical field distribution around a biological body by an optical technique

AbstractWhen a biological body enters a uniform unperturbed field, the field is distorted by the body and the field concentration occurs on various parts of the body. To elucidate the biological effects of strong electric field, the coupling of the electric field to a biological body has to be well understood and the field exposure dose to a biological body has to be evaluated qualitatively. Using an optical field sensor with a minimum field perturbation, we have developed a system which can visualize the spatial distribution of the field around an object with a complex shape such as a biological body. First, the accuracy of the measurement was confirmed through comparison between the measurement and theoretical calculation using the model with a simple geometry. Second, the field distributions were measured with experimental animals and it was shown that a conductor model can be used instead of a living body in this frequency range. Based on these results, the field distributions were measured with a human model in various conditions found in common everyday life. These results will provide useful information on the behavior of the field around a human body.

Depletion layer formation rate at T<30 °K in buried channel, metal-oxide-semiconductor transistors

Measurements of depletion layer formation rates in buried channel silicon, metal-oxide-semiconductor devices at carrier freeze-out temperatures are presented. The procedure is based on the current injected into the gate region by a pulsed gate bias and the dependence of this injection current on the pulse frequency. This method avoids strong electric field effects (field-enhanced emission) and a response due to surface state trapping. In addition to describing a new dynamic response effect in metal-oxide-semiconductor transistors at low temperatures, the measured activation energy of the arsenic dopant is found to be 54.2 meV, in close agreement with the accepted ionization energy.

Real and apparent effects of strong electric fields on the electron emission from midgap levels EL2 and EL0 in GaAs

The effects of strong electric fields, up to 4×105 V/cm, on the electron emission from the GaAs dominant midgap levels EL2 and EL0 were investigated by employing differential capacitance transients on GaAs-Au Schottky diodes. It was found that, in diodes with normal reverse bias characteristics, both levels exhibited a small field enhancement of electron emission, well within the range of the Poole–Frenkel effect. In contrast, very pronounced ‘‘apparent’’ electric field effects were observed in diodes with large reverse bias current. Thus, the conflicting reported results on the magnitude of the field enhancement of the electron emission from EL2 must be attributed to the characteristics of the Schottky diodes employed rather than to those of EL2.

The effect of strong electric fields on exotic negative ions in He II: Possible evidence for the nucleation of charged vortex rings

We present evidence suggesting that Ihas and Sanders' intermediate mobility exotic negative ions can nucleate quantised vortex rings in superfluid 4He when subjected to strong enough electric fields.