Nonlinear Electrical Response Research Articles

Electric response properties of a confined gas of independent particles acted upon by a direct current electric field

Exact results for linear and nonlinear electric response properties of a non-interacting ensemble of charged particles, confined within an impenetrable box and subjected to a static, homogeneous electric field, are derived and discussed.

Nonlinear conduction of charge-density wave in the quantum Hall regime of η-Mo 4O 11

Nonlinear pulsed electric field response of charge-density wave (CDW) in η-Mo 4O 11 has been measured in magnetic fields where the quantum Hall effect (QHE) is observable. We have found that the relaxation time characterizing the sliding motion of CDW condensates shows pronounced peaks at magnetic fields corresponding to the Hall plateaus, which strongly suggests that a charge transfer from the CDW condensate system to the quantized carrier (QHE) system occurs.

Comparison of nonlinear and nonstationary response of conventional and resonant cavity enhanced p-i-n photodiode

High-power illumination of a p-i-n photodiode results in nonlinear operating conditions and, of course, in nonlinear electric response. This article presents an investigation and comparison of the nonlinear response of conventional and resonant cavity enhanced (RCE) p-i-n photodiodes constructed using a two-valley semiconductor (GaAs). The presented results are obtained through numerical simulation of the complete phenomenological model for a two-valley semiconductor in the submicron region for several bias voltages and several values of Dirac pulse optical powers. The nonlinear behavior is analyzed through carrier transit and response time. Nonstationary effects exist in two-valley semiconductors in the presence of adequate perturbation of the electric field in the absorption layer. The present investigation shows that the RCE p-i-n photodiode reaches the nonlinear operating regime for smaller incident optical irradiances.

Major intermolecular effects on nonlinear electrical response in a hexatriene model of solid state polyacetylene

Through detailed model studies, benchmarked by extensive ab initio calculations, we show (1) how sizable medium effects on molecular electrical response of polymeric solids can arise; (2) that classical electrostatics accurately reproduces a full quantum treatment; and (3) that for a large bundle of hexatriene molecules taken as a model of polyacetylene, the medium effect will lead to as much as a 95% reduction in the second hyperpolarizability and a 50% reduction in the polarizability. For designing organic materials with enhanced nonlinear optical (NLO) properties, the results reveal features that might be optimized and point to a sound model for selecting other features.

Nonlinear electric response of YBa 2Cu 4O 8 ceramics at the inter-grain superconductive ordering

Linear and nonlinear electric response to the external AC current is observed in superconductive ceramics of a stoichiometric compound, YBa 2Cu 4O 8. A broad negative anomaly of a third-harmonic in-phase component V′ 3ω is found around the inter-grain ordering temperature T C2 determined by previous magnetic measurements. The anomaly gets remarkable with decreasing AC current keeping the maximum position constant. From these results, a negative divergent anomaly of nonlinear electric response is suggested as an intrinsic critical phenomenon of inter-grain ordering in this system.

Use of AL307 light-emitting diodes as photodetectors for diagnostics of femtosecond light pulses

A nonlinear electrical response has been observed for the first time from AL307 light-emitting diodes exposed to femtosecond light pulses. When used in an unconventional fashion as unbiased photodiodes, these AL307 light-emitting diodes give an electrical response proportional to the square of the recorded radiation intensity of ultrashort light pulses. Autocorrelation functions are given for femtosecond pulses obtained using AL307 light-emitting diodes in the autocorrelator instead of the conventional photodetector and nonlinear crystal system.

Alternating current conductivity of iron(III)-phthalocyanine grafted poly(N-vinylcarbazole)

Abstract Differences in alternating current conductivity measurements carried out on Fe(III)-phthalocyanine grafted poly(N-vinylcarbazole), compared to that of the fresh polymer, are attributed to both the linking chemical group involved and resonant structures developed. Polar and magnetic characteristics of the samples create capacitative and inductive behaviors. Frequency and temperature variations cause nonlinear electrical responses and enhanced conductivities up to 6 orders of magnitude, a.c. conductivity values, over 10−2 S m−1 obtained at discrete frequency and temperature values, are unusual responses of electrical measurements in vinylaromatic-based semiconducting polymer materials. Experiments using varying temperatures from room temperature to 200°C, gave conductivity peaks that are heating rate dependent. The bond flexibility of the link between the metal-phthalocyanine and polymer is of primary importance to the conduction behavior.

Nonlinear dc electrical response in a bilayer lipid membrane: Effect of bathing solutions.

The physical origin of a nonlinear electrical response in a bilayer lipid membrane (BLM) separating two aqueous bathing solutions has been attributed by earlier workers to field induced pore formation in the lipid moiety, which provides ionic pathways. Recently, we reported similar nonlinearity in the absence of any ion source, viz., in solid films of lipids. The study ruled out the possibility of pore formation being the only mechanism of transmembrane conductance. Using the BLM of oxidized cholesterol in n-decane, we report here our studies on the role of bathing soution on the I-V characteristics of these membranes. The nonlinearity is maintained in the presence of an electron donor as well as an electron acceptor in the bathing solution, although there is a distinct difference in the nature of the nonlinearity in the two cases. Our results indicate that three factors, namely, pore formation, the semiconducting properties of the constituent lipid molecules, and the mechanism of transmembrane charge transport, are responsible for the observed nonlinearity.

High optical power nonlinear dynamic response of AlInAs/GaInAs MSM photodiode

In this paper, we introduce a theoretical study and a numerical simulation of the nonlinear electrical response, including the harmonic-generation rate calculation, of an MSM AlInAs/GaInAs photodiode under high-illumination conditions. We also report that, with an MSM operating at 20 GHz, we can expect a saturation limit at a maximum modulated optical power as high as 100 mW. >

Collective pinning of vortices in very thin amorphous Mo79Ge21 films.

The collective pinning of vortices in very thin amorphous superconducting films is experimentally investigated by a systematic study of the nonlinear electrical response of ${\mathrm{Mo}}_{\mathit{x}}$${\mathrm{Ge}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ (x=79%) alloy films of various thickness measured in perpendicular magnetic field. In the thickest of these films, the standard collective pinning analysis yields an unusual field dependence of the pinning force, suggesting that more than one type of pinning center may play a substantial role. We then examine the field dependence of the pinning forces in progressively thinner samples. In the thinnest films the influence of the additional pinning centers in this system appears to be less pronounced than in thicker films, although the interplay between changes in the microscopic pinning and the breakdown of the standard collective pinning picture remains to be clarified.

Electrical response of heterogeneous systems and Debye's problem.

We study the linear and nonlinear electric response of heterogeneous systems containing inclusions of arbitrary structure and permanent multipole moments of all orders with L=0 and L=1 pair distributions, within mean field theory. We find that for these distributions only the dipole moments contribute to the effective dielectric function. In particular, we provide the results for inclusions without permanent dipole moments or polarizabilities, and spherical inclusions. We show that the Debye's effective dielectric function represents the linear part of the general result, in the special case of spherical inclusions with isotropic (L=0) pair distributions.

Evidence of anomalous hopping and tunneling effects on the conductivity of a fractal Pt-film system.

The temperature dependence of the conductance and the nonlinear electrical response of a Pt-film percolation system, deposited on fracture surfaces of \ensuremath{\alpha}-${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ ceramics, have been measured over three decades of sheet resistance. We find that in the temperature interval of T=77--300 K, the resistance temperature coefficient \ensuremath{\beta}=(1/R)dR/dT is not a constant, which is different from that for flat films. A dc I-V characteristic which strongly depends on the thickness of the film is found and it can be interpreted as a competition among the local Joule heating, hopping, and tunneling effects. The third-harmonic measurement suggests that the critical exponent comes from 1/f noise, which obeys the power-law dependences ${\mathit{S}}_{\mathit{R}}$\ensuremath{\propto}(p-${\mathit{p}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\kappa}}}$, R\ensuremath{\propto}(p-${\mathit{p}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{-}}\mathit{t}}$, and then ${\mathit{S}}_{\mathit{R}}$\ensuremath{\propto}${\mathit{R}}^{\mathit{w}}$ with w=\ensuremath{\kappa}/t, where ${\mathit{S}}_{\mathit{R}}$ is the mean square of resistance fluctuations, p the surface coverage fraction, and ${\mathit{p}}_{\mathit{c}}$ its percolation critical value. We find that w=0.45\ifmmode\pm\else\textpm\fi{}0.06, which is lower than the flat-film exponent. This result indicates that the tunneling and hopping effects in the fractal samples are much stronger than that of flat films.

Anomalous temperature dependence of vortex elastic properties in the flux-flow regime of Mo77Ge23/Ge multilayer superconductors.

We report nonlinear electrical response in superconducting/insulating ${\mathrm{Mo}}_{77}$${\mathrm{Ge}}_{23}$/Ge multilayers. In low-anisotropy multilayers, we observe an abrupt change in the current-voltage characteristic as a function of temperature. This change corresponds to a sharp drop in the pinning drag force acting on moving vortices in the flux-flow regime at low temperatures. The decrease in pinning drag force may be related to an abrupt increase in the rigidity of the system of moving vortices.

Nonlinear electrical response and breakdown of semicontinuous metal films

The weakly nonlinear electrical response, determined by 3rd harmonic generation, and the breakdown current I b of percolating systems are measured in real materials: semicontinuous Ag and Au films. The 3rd harmonic is interpreted as a direct measure of the 4th moment of the current distribution, and thus provides the critical exponent κ (normally determined by 1/ƒ noise measurements). Observations of higher harmonics (5th and 7th), corresponding to higher moments of the current distribution, provide an estimation of higher critical indices. The breakdown current I b was measured over three decades of film resistance. A new criterion for I b is suggested, defined as the current at which a hot spot reaches the melting temperature of the metallic grains T m. This criterion remains valid in the presence of nonlinear effects. The hot spot model yields a power law I b ∞ B - x , B=V 3ƒ/I 3 where the upper and lower bounds of x are found to be 0.5 (extreme case of continuum percolation) and 0.36 (lattice percolation lower bound), respectively, in excellent agreement with the measured data.

THE ROLE OF MICROGEOMETRY IN THE ELECTRICAL BREAKDOWN OF METAL-INSULATOR MIXTURES

The breakdown phenomena of percolative metal-insulator composites and their extreme sensitivity to fine details of the microgeometry are discussed, for three different cases: the critical current of superconductor-insulator mixtures (or superconductor-normal metal); the dielectric breakdown of metal-insulator composites below the percolation threshold (insulating regime); and the electrical breakdown above the metal-insulator transition (metallic regime). Two experimental techniques for characterizing the microgeometry are described: (a) 1/f noise measurements, which provide the fourth moment of the current distribution; (b) the harmonic generation method, where the weakly nonlinear electrical response due to local Joule heating provides information on the fourth (and higher) moment of the current distribution.

Nonstationary and nonlinear response of a p-i-n photodiode made of a two-valley semiconductor

The influence of nonstationary and nonlinear effects on carrier transport in a p-i-n photodiode made of a two-valley semiconductor is analyzed. A phenomenological model based on a two-valley conduction-band model is used, incorporating transition rates for intervalley electron transfer into the continuity equations and the drift-diffusion equations for carrier transport. A large optical power absorption in a small device can perturb, via the space-charge potential, the electric field which governs the carrier transport, and thus give rise to a nonlinear electrical response. The influence of these effects on photodiode response to pulsed light stimulation under various reverse-bias voltages is calculated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The temperature dependence of the non-linear electrical response in HTSC

The dependence of the non-ohmic behaviour on the temperature in HTSC is strongly influenced by the interaction between the CuO 2 planes. The effect is studied on the basis of a Kosteritz-Thouless model developed for quasi-bidimensional superconductors and the results are used to explain the non-linear current-voltage characteristics in some YBCO and BSCCO samples. The anisotropy and the ratio n/ m ∗ (supercarrier density/effective mass) are evaluated.

Third-harmonic generation in semicontinuous metal films.

The weak nonlinear electrical response of two-dimensional semicontinuous Ag and Au films was measured over three decades of sheet resistance. The third-harmonic component generated by the films, due to local Joule heating, is interpreted as a measure of the fourth moment of the current distribution. Higher harmonics corresponding to higher moments of the current distribution were also observed. Under certain conditions, measurement of the third harmonic lends the same critical exponent as that of 1/f noise, which obeys a power-law dependence ${\mathit{S}}_{\mathit{R}}$\ensuremath{\propto}(p-${\mathit{p}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\kappa}}}$, where ${\mathit{S}}_{\mathit{R}}$ is the mean square of resistance fluctuations, p the surface coverage fraction, and ${\mathit{p}}_{\mathit{c}}$ its critical value where the metal-insulator transition occurs. The film resistance obeys another power law R\ensuremath{\propto}(p-${\mathit{p}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{-}}\mathit{t}}$, hence ${\mathit{S}}_{\mathit{R}}$\ensuremath{\propto}${\mathit{R}}^{\mathit{w}}$ with w=\ensuremath{\kappa}/t. We have found that w=1.2\ifmmode\pm\else\textpm\fi{}0.1 for Ag samples, which is somewhat higher, but close to the lattice percolation value (random resistor network: 0.82w1.05). For the Au samples, w=1.65\ifmmode\pm\else\textpm\fi{}0.15, which is higher than the lattice percolation exponent and lower than the Swiss-cheese-model continuum percolation estimate (w&gt;4.5). Comparison of our data on gold films with 1/f noise measurements on similar samples suggests the equivalence of these two techniques in probing the microgeometry details.

Osmotically induced electrical signals from actin filaments

Actin filaments, F-actin, a major component of the cortical cytoskeleton, play an important role in a variety of cell functions. In this report we have assessed the role of osmotic stress on the electrochemical properties of F-actin. The spontaneous Donnan potential of a polymerized actin solution (5 mg/ml) was -3.93 +/- 1.84 mV, which was linearly reduced by osmotic stress on the order of 1-20 mOsm (0.28 +/- 0.06 mV/mM). Calculated surface charge density was reduced and eventually reversed by increasing the osmotic stress as expected for a phase transition behavior. The electro-osmotic behavior of F-actin disappeared at pH 5.5 and was dependent on its filamentous nature. Furthermore, osmotically stressed F-actin displayed a nonlinear electric response upon application of electric fields on the order of 500-2,000 V/cm. These data indicate that F-actin in solution may display nonideal electro-osmotic properties consistent with ionic "cable" behavior which may be of biological significance in the processing and conduction of electrical signals within the cellular compartment.

The extrinsic nature of nonlinear behavior observed in lead zirconate titanate ferroelectric ceramic

The nonlinear electric and electromechanical responses of lead zirconate titanate Pb(ZrxTi1−x)O3 ceramics to an external ac electric field have been measured under different driving levels. The onset of measurable nonlinearity is observed to be accompanied by the appearance of hysteresis loops. This lossy nature suggests that the nonlinearities in a ferroelectric ceramic are generated by the domain-wall motion. In addition, aging experiments and the bias field dependence of the threshold field (onset of nonlinearity) all indicate the extrinsic nature of the nonlinear behavior of ferroelectric ceramics. A phenomenological theory of Arlt, Dederichs, and Herbiet [Ferroelectrics 74, 34 (1987)] has been extended to include the nonlinear contributions. With only 90° wall vibration being considered, the theory leads to some basic understanding of the experimental results.