Charge Fluctuation Model Research Articles

Radiation-Induced Junction-Leakage Random-Telegraph-Signal

The paper studies the radiation effects on the junction leakage random telegraph signal (JL-RTS). Using arrays of transistors, a statistical study of the phenomenon in MOSFETs source p-n junctions is performed and the impact of the electric field, the type of irradiation, and the source design is investigated. It appears that although JL-RTS originate both from the DDD- and TID-induced defects, the latter is the dominant contribution in MOSFETs sources due to an electric field enhancement. The paper then completes the study with ab initio molecular simulations to investigate the origin of the JL-RTS. The results advocate for the adoption of the structural fluctuation model over the state charge fluctuation model to describe the origin of the phenomenon.

Junction Leakage Random Telegraph Signals in Arrays of MOSFETs

This letter presents an experimental study of the junction leakage RTS (JL-RTS) in a large set of MOSFET p-n junctions. Arrays of MOSFETs are used to statistically study the effects of the temperature, the electric field, and the source/drain design. The results, supported by ab initio molecular dynamic simulations, advocate for the adoption of the structural fluctuation model over the state charge fluctuation model to describe the defects at the origin of the phenomena.

Retraction of "Extension to the Charge Fluctuation Model for the Prediction of the Conductivity of Apolar, Reverse Micellar Systems". Langmuir 2012, 28 (45), 15751-5.

ADVERTISEMENT RETURN TO ISSUEPREVRetractionNEXTRetraction of “Extension to the Charge Fluctuation Model for the Prediction of the Conductivity of Apolar, Reverse Micellar Systems”Edward L. Michor and John C. Berg*Cite this: Langmuir 2016, 32, 10, 2525–2526Publication Date (Web):March 4, 2016Publication History Published online4 March 2016Published inissue 15 March 2016https://doi.org/10.1021/acs.langmuir.6b00129Copyright © 2016 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views832Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (381 KB) Get e-Alerts Get e-Alerts

Physicochemical characterization of water-in-oil microemulsions formed by a binary 1,3-dioxolane alkyl ethoxylate/Aerosol-OT surfactant system

The physicochemical behavior of the binary surfactant system consisting of the ionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate, or Aerosol-OT (AOT), and the two-tailed cyclic ketal alkyl ethoxylate (2-tridecyl, 2-ethyl-1,3-dioxolan-4-yl) methoxy]-O′-methoxy poly(ethylene glycol)], or CK-2,13, in water/isooctane water-in-oil (w/o-) microemulsion systems enriched in AOT was performed to understand the arrangement of the two surfactants at the interface and the behavior and properties of the microemulsion systems to enable applications. Many of the properties observed were similar to microemulsions formed by AOT/C12E4 or C12E5, the latter two being linear alkyl ethoxylates of comparable tail length and average ethoxylate size, including a decrease of water solubilization and increase of attractive interactions with an increase of ethoxylate surfactant concentration, the latter determined via small-angle neutron scattering (SANS). SANS also demonstrated that the increase of the CK-2,13 fraction among the surfactants from 0.1 to 0.2 to 0.3 induced a change in shape from spheres to ellipsoids to cylinders, a trend not reported for AOT/CiEj binary mixtures, and that the surface area per CK-2,13 molecule was approximately 35Å2, nearly identical to the value reported for C12E5. Profiles of electrical conductivity versus the water-surfactant mole ratio (W0) for microemulsions prepared at low surfactant concentrations (far below the percolation threshold) were bell-shaped, consistent with the charge-fluctuation model, and shifted to lower W0 as the alkyl ethoxylate fraction was increased. The extent of the shift was greater for CK-2,13 than for an equal proportion of C12E4, suggesting CK-2,13 possesses a more profound influence on microemulsion properties. Analysis of the OH stretching region (3100–3700cm−1) of the Fourier Transform Infrared Spectroscopic spectrum for w/o-microemulsions demonstrated that an increase of the CK-2,13 content of the total surfactant led to an increase of water molecules localized near the Na+ counterion of AOT of 0.7mol water per mol surfactant, suggesting the water molecules of hydration for the ethoxylate group reside near AOT's counterion, resulting in increased dissociation of the counterion, hence to an increased hydrophilicity for AOT.

Extension to the Charge Fluctuation Model for the Prediction of the Conductivity of Apolar, Reverse Micellar Systems

This paper presents an extension to current theory regarding charging behavior in apolar, micellar systems. Electrical conductivity in such systems accompanying the formation of neutral reverse micelles is commonly explained by the possibility of intermicellar collisions resulting in a pair of oppositely charged micelles. The sequestration of the resulting charges within the micelles prevents their immediate recombination. The current theory underlying the charging process has thus far been applied in only approximate form, and is only used to validate experimental trends and to abstract values for the fraction of charged micelles. The extended theory proposed here uses knowledge of the solvent and surfactant characteristics, together with water content, to predict solution conductivity in absolute terms. It is verified in experiments with the solvent Isopar-L and surfactants Aerosol OT, OLOA 11000, and Span 80, in which significant differences from the approximate theory are observed.

Structure and reactivity of the mixed‐valence CaMn4O5(H2O)4 and CaMn4O4(OH)(H2O)4 clusters at oxygen evolution complex of photosystem II. Hybrid DFT (UB3LYP and UBHandHLYP) calculations

AbstractVery recently Umena et al. have determined the X‐ray diffraction (XRD) structure of the CaMn4O5 cluster in the oxygen evolution complex (OEC) of photosystem II (PSII) refined to 1.9 Å resolution. We have performed theoretical attempts to elucidate possible electronic and spin states of their new XRD structure of the CaMn4O5 cluster. For the purpose, hybrid density functional theory (UB3LYP and UBHandHLYP) calculations have been performed for the mixed‐valence (MV) CaMn(III)4‐ω(IV)ωO5(H2O)4 (1) and CaMn(III)4‐ω(IV)ωO4(OH)(H2O)4 (2) clusters as active catalytic site for water splitting reaction in OEC of PSII. Full geometry optimizations of 1a (ω = 2) and 2a (ω = 2) have been performed to elucidate scope and limitation of the cluster models. Both charge and spin fluctuated structures (48 UB3LYP solutions) have been considered for the MV 1a (ω = 2). Total energies obtained by these calculations have elucidated quasi‐degenerated electronic and spin states that are characterized by charge and spin density populations. The energy levels revealed by hybrid DFT are analyzed on the basis of the Heisenberg spin Hamiltonian model, providing the effective exchange integrals between manganese ions at a uniform or MV structure. The spin projections for hybrid DFT solutions are performed using the effective exchange integrals. The charge fluctuation model is introduced to analyze relative stabilities among MV structures of 1a and 2a. These computational results for 1a and 2a have explored several characteristic electronic properties of the species that are used for theoretical elucidation of possible mechanisms of water splitting reaction. Orbital and spin correlation diagrams are derived for the OO bond formation and oxygen evolution in the reaction. Implications of the computational results are also discussed in relation to available experiments and theoretical results by other groups. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012

Evidence for valence-charge fluctuations in the3×3−Pb∕Si(111)system

We have investigated the 1/3 monolayer $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\text{\ensuremath{-}}\mathrm{Pb}∕\mathrm{Si}(111)$ system with core level photoemission at temperatures of 300 and $120\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. At both temperatures the $\mathrm{Pb}\phantom{\rule{0.3em}{0ex}}5{d}_{5∕2}$ and $5{d}_{3∕2}$ core levels are split into two states with an intensity ratio of 2:1, as in the related $\mathrm{Sn}∕\mathrm{Ge}(111)$ and $\mathrm{Sn}∕\mathrm{Si}(111)$ systems. On doping the surface with $\mathrm{Cs}$ (an electron donor) or oxygen (an electron acceptor) the ratio of the intensities of the two states change strongly, suggesting the states have filled or empty dangling bonds. The results are interpreted in terms of charge fluctuations with one third of $\mathrm{Pb}$ atoms acting as charge donors and two thirds as acceptors in the undoped phase. Four chemically shifted $\mathrm{Si}\phantom{\rule{0.3em}{0ex}}2p$ core level peaks are found whose energies are almost constant for the doped and undoped surfaces, and whose relative intensities change significantly on doping. These states of $\mathrm{Si}$ are assigned to two distinct kinds of atoms bonded to the two states of $\mathrm{Pb}$, and to deeper $\mathrm{Si}$ atoms. The shifts are explained in the framework of the charge fluctuation model [M. G\othelid, M. Bj\orkvist, T. M. Grehk, G. Le Lay, and U. O. Karlsson, Phys. Rev. B 52, R14 352 (1995)], and the integer pseudo charge model [G. Ballabio, G. Profeta, S. de Gironcoli, S. Scandolo, G. E. Santoro, and E. Tosatti, Phys. Rev. Lett. 89, 126803 (2002)]. Within the family of group IV metals adsorbed on group IV (111) semiconductor surfaces, $\mathrm{Pb}∕\mathrm{Si}(111)$ is similar to $\mathrm{Pb}∕\mathrm{Ge}(111)$ and $\mathrm{Sn}∕\mathrm{Ge}(111)$ with $\mathrm{Sn}∕\mathrm{Si}(111)$ being the exceptional case.

Conductivity of water-in-oil microemulsions stabilized by mixed surfactants

The electrical conductivity of D 2O-in- n-heptane microemulsions stabilized by cationic/nonionic surfactant mixtures was studied as a function of D 2O content, surfactant concentration, and surfactant mixture composition. The surfactants employed were cationic di- n-didodecyldimethylammonium bromide, DDAB, nonionic poly(oxyethylene) monododecyl ethers, C 12E J , with J=3–8 and 23, nonionic polymeric surfactants of the type PEO–PPO–PEO (Pluronic), and the reverse structure analogues (Pluronic R). Qualitative structural information was drawn from a comparison between the measured conductivity and that predicted by the charge fluctuation model for spherical droplets. The conductivity versus water content curves were found to be typical for water-in-oil systems composed of spherical droplets. From the effect of blending nonionic surfactant with DDAB on the measured conductivities, it was concluded that microemulsion conductivity is independent of the concentration of cationic surfactant (DDAB). This finding agrees well with theoretical microemulsion conductivity models.

Conductivity of mixed surfactant water-in-oil microemulsions

The electrical conductivity of D2O-in-n-heptane (or in-p-xylene) microemulsions stabilized by a mixture of the cationic surfactant di-n-didodecyldimethylammonium bromide, DDAB, and either the CIEJ non-ionic surfactants, or polymeric nonionic surfactants of the type PEO-PPO-PEO, Pluronic®, was investigated as a function of D2O content and surfactant mixture composition. It was found that the change in conductivity as a result of partially replacing the cationic surfactant by the non-ionic is due to the change in droplet size, and not a decrease in ionic strength. This was concluded from the following observations: (1) when the droplet size was held constant, the conductivity was constant even for samples with different water droplet ionic strengths, (2) good agreement was found between the measured conductivities and those predicted by charge fluctuation model (CFM) even though the ionic strength (not considered in CFM) is varied, and finally (3) graphical analyses of conductivities for microemulsions stabilized by different cationic-nonionic surfactant mixtures result in curves similar to those expected for microemulsions stabilized by ionic surfactant only. These results show clearly that mixing cationic and non-ionic surfactants is useful in testing and supporting microemulsion conductivity models.

Microstructure and Dynamics of the Water-in-Oil CTAB/n-Pentanol/n-Hexane/Water Microemulsion: A Spectroscopic and Conductivity Study

Quaternary water-in-oil microemulsion of a cationic surfactant (cetyltrimethylammonium bromide, CTAB), n-hexane, water, and n-pentanol has been investigated using conductivity, quasi-elastic light scattering, near-infrared absorption spectroscopy, and pulsed field gradient spin-echo NMR measurements. The conductivity behavior shows features characteristic of the migration of charged droplets. Consequently, using the charge fluctuation model, the conductivity data were correlated with the droplet radius obtained from self-diffusion coefficients for different obstruction factors. Conductivity and self-diffusion measurements were found to be self-consistent for spherical droplets with hard-sphere interactions. Comparison between collective diffusion and self-diffusion coefficients fully supports this conclusion. The average head-group area of CTAB, the amount of water free in the organic bulk, and the fraction of alcohol present into the aggregates were evaluated together with the thickness of both the inter...

Conductivity of water-in-oil microemulsions: Fluctuations from the charge generation-recombination equilibrium

A theory for conductivity fluctuations in water-in-oil microemulsions is presented. The treatment is based on the charge fluctuations model proposed by Eicke et al., Hall, and Halle. The portion of current fluctuations due to fluctuations in the number of charge carriers is attributed to the charge generation-recombination equilibrium: two neutral drops ⇌ positive drop+negative drop. The power spectrum of the fluctuations is a Lorentzian determined by the forward and reverse rates of this equilibrium. Implications of the charge fluctuation model for experimental studies of water-in-oil microemulsions are suggested.

Lattice dynamics of La 2NiO 4 in the charge fluctuation model

The lattice dynamics of La 2NiO 4 is calculated in the framework of a description of the electronic density response recently applied to the high-temperature superconductors (HTSC). The local part of the density response is approximated by a proper ab initio ionic model of rigid ions to represent the effects of the ionic forces in the crystal. The structure parameters and the phonon dispersion curves are investigated in this model and are compared with recent interpretations of the experimental data. Additionally, nonlocal contributions to the density response in the form of charge fluctuations at the ions are considered and their influence on the dispersion is discussed. From our results we find that some corrections of the current interpretation of the experimental data may be appropriate. Finally, the importance of phonon-induced charge fluctuations for the HTSC is emphasized.

Conductivity of water-in-oil microemulsions: Comparison of the Boltzmann statistics and the charge fluctuation model

The electrical conductivity of water-in-oil microemulsions is interpreted on the basis of the distribution of ionic charges among the droplets. The charging energy is approximated by the Born energy. In the interpretation, the hydrodynamic radius is distinguished from the water core radius. The Boltzmann statistics are compared with the fluctuation theory. The former approach is more realistic due to its consideration of the discrete nature of charge, while the latter better fits the data obtained with the AOT-water-isooctane system.

The charge fluctuation model for the conductivity of a microemulsion

The charge fluctuation model for the conductivity of a microemulsion is further investigated, two conclusions are drawn: (1) This model may be based on the thermodynamic fluctuation theory in a general and rigorous way. (2) A “semi-classical” expansion of Hall's improved formula may be given, with the corresponding formula of Eicke as the first approximation.

Characteristics of mixed phase superconductivity in oxygenated La 2CuO 4+δ

Superoxygenated La 2CuO 4+δ, produced at 1800 atm and 550°C, has been investigated by the following means; resistivity, Seebeck coefficient Hall coefficient, magneto-resistance, electron microscopy, AC and DC susceptibility, and specific heat. The results are contrasted with those from “reduced” (stoichiometric) La 2CuO 4. Unlike the latter Mott insulator, the oxygenated material shows mixed valent, delocalized behaviour. That behaviour is rendered more complex because of phase segregation via spinodal decomposition onsetting just below room temperature. The observed microstructure permits detailed interpretation of the resulting modification in properties. The degree to which the observed superconductivity mirrors that of (La/Sr) 2CuO 4 is discussed. Restricting the phase segregation by fast cooling inhibits the superconductive behaviour, by promoting lower effective carrier counts and mobilities and greater magnetic admixture. It is shown that phase segregation is not triggered by or coupled to the point at which long-range 3D magnetic order develops within the insulating component of the two-phase mixture. The super-conductivity is presented in terms of the negative- U charge fluctuation model developed earlier.

Conductivity of microemulsions: refinement of charge fluctuation model

The aim of this Comment is to propose a refined theoretical treatment by distinguishing the Born radius of droplets from the Stockes radius. It will be demonstrated that such an approach improves the concordance between the theory and experiments over the whole range of sizes of microemulsion droplets

Theory and experiment of electrical conductivity and percolation locus in water-in-oil microemulsions.

An extensive set of measurements of low-frequency conductivity \ensuremath{\sigma} of a three-component microemulsion system, sodium-di-2-ethyl-hexylsulfosuccinate (AOT)-water-decane, as a function of temperature (T from 10 to 50 \ifmmode^\circ\else\textdegree\fi{}C) and volume fraction of the dispersed phase (\ensuremath{\varphi} from 0.098 to 0.65) has been made. The measurements were made at a fixed value of the water-to-surfactant molar ratio equal to 40.8, where the microemulsion consists of AOT-coated water droplets, 85 \AA{} in radius, dispersed in oil. \ensuremath{\sigma} can be quantitatively calculated at low \ensuremath{\varphi} by means of a charge fluctuation model of Eicke et al., while it can be interpreted for higher vlaues of \ensuremath{\varphi} in terms of power-law behavior with indices related to the dynamic percolation picture below the threshold and the static one above it. The percolation locus in \ensuremath{\varphi}-T plane has been determined starting from the vicinity of the lower consolute point up to \ensuremath{\varphi}=0.65. This line can be successfully interpreted in terms of a modified version of the analytical theory of percolation given by Xu and Stell.

Conductivity of microemulsions: an improved charge fluctuation model

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConductivity of microemulsions: an improved charge fluctuation modelDenver G. HallCite this: J. Phys. Chem. 1990, 94, 1, 429–430Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://doi.org/10.1021/j100364a072RIGHTS & PERMISSIONSArticle Views174Altmetric-Citations61LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (214 KB) Get e-Alerts

Far infrared absorption spectra of amorphous (As2S3)?(Sb2S3) semiconductors and the spatial charge fluctuation

Far infrared absorption spectra of amorphous (As2S3)1−x(Sb2S3)x system (x=0.0∼0.6) were measured in the wavenumber region 7∼25 cm−1 with Lamellar grating far infrared Fourier Transform Spectrometer, and the spatial fluctuation of charges and its correlation range were estimated with charge fluctuation model. The charge fluctuation of (As2S3)1−x(Sb2S3)x system increases with Sb2S3 concentration x. On the other hand, the correlation length of the charge fluctuation decreases from 7 A to 4.5 A with an increase in x. As a result, it can be found that the medium range order of As2S3 changes drastically with an incease in Sb2S3 concentration x.

Three-band charge fluctuation model for electron pairing: A many-body calculation.

We apply many-body techniques to the study of a model Hamiltonian with on-site and nearest-neighbor Coulomb interactions. We calculate polarization propagators and effective interactions. Our results give support to a charge fluctuation mechanism for pairing.