Non-ohmic Conduction Research Articles

Non-Ohmic conduction in glow-discharge a-Si:H films

Abstract Non-Ohmic conduction in undoped glow-discharge a-Si:H films has been studied using sandwich configurations. It is found that the conductivity at low temperatures is field-dependent and varies with field in the manner σ = σo(T) exp (AeV/kT) over most of the field range used in the experiment, where A is a weak function of temperature T and V is the applied voltage. For voltages less than 1 V, the electric field does not change the temperature dependence of conductivity and the Mott T −1/4 law is obeyed at low temperatures. The effect of light soaking is also described in this Letter and the results show that the low-temperature non-Ohmic conductivity remains almost unchanged after illumination while the high-temperature Ohmic conductivity drops significantly.

The quasi-one-dimensional conductor under uniaxial strain: non-ohmic conduction and dc-induced voltage oscillations in orthorhombic TaS 3

Recent experiments on non-ohmic conduction α nl and dc induced voltage oscillations VO (“narrow band noise”) in deformed o-TaS 3 are reviewed. A drop of α nl and an almost full depression of VO at some particular value of a strain deformation S c are interpreted in terms of a model associating both phenomena with existence of kinks (CDW phase discommensurations).

Non-ohmic conduction in doped polyacetylene at low temperatures

The electrical conductivity of a iodine-doped polyacetylene is measured as a function of the electric field ℰ at temperatures between 4K and 0.3K. We find that after an initial non-linear behavior σ increases linearly with ℰ in agreement with a theoretical description based on variable-range hopping conduction. The non-linear rise at low fields depends on the iodine concentration. In heavily doped samples the increase is small and varies as ℰ2, whereas in less conductive samples a large change is observed at 0.3K which varies approximately as log ℰ for fields from 1 V/m to 150 V/m.

Coupled Two Dimensional Electron Gas Structures in the G1−xAlxAs/GaAs System

ABSTRACTTwo 2-dimensional electron gas (DEG) regions coupled either by a superlattice, an undoped GaAs layer, or the combination of a tunneling barrier with a superlattice have been investigated by studying (a) non-ohmic conduction, (b) field effect characteristics parallel to the 2DEG channels and (c) negative differential resistance (NDR) for conduction perpendicular to the quantum wells. It is shown that coupling is optimized when the separation region is a superlattice. Tunneling through superlattice mini-bands can enhance field effect transistor transconductance.

Non-ohmic conduction and electrical switching under pressure of the charge transfer complexo-tolidine-iodine

The current voltage characteristics ofo-tolidine-iodine, with stoichiometry 1:1 grown from benzene, have been studied under high pressures upto 6 GPa atT=300 K andT=77 K. The characteristics show a pronounced deviation from ohmicity beyond a certain current for all pressures studied. At room temperature, beyond a threshold field the system switches from a low conductingOFF state to a high conductingON state with σON/σOFF ∼ 103. TheOFF state can be restored by the application of an a.c. pulse of low frequency. The temperature dependence of the two states studied indicates that theOFF state is semiconducting while theON state, beyond a certain applied pressure is metallic. The characteristics atT=77 K do not show any switching.

Non-ohmic electric conduction in polycrystalline thulium oxide

The current voltage behaviour of polycrystalline Tm2O3 has been investigated at 77 K and 300 K to 350 K. At low voltages, the conduction is ohmic while at higher voltages the current has a quadratic dependence on voltage. The voltageV T at which the transition from ohmic to non-ohmic conduction takes place changes from 180 V to 100 V as temperature increases from 77 K to 350 K. The results are interpreted in terms of the Rose theory of space charge limited currents (sclc) in defect insulators containing shallow traps.

Electric field dependence of the Raman phonon in the charge-density-wave state of TaS3.

The effect of the electric field on one of the Raman phonons (\ensuremath{\sim}285 ${\mathrm{cm}}^{\ensuremath{-}1}$) is studied in the chargedensity-wave state of orthorhombic Ta${\mathrm{S}}_{3}$. The phonon frequency decreases when the field exceeds the threshold for non-Ohmic conduction. Several mechanisms which may lead to phonon softening in the current-carrying state are considered.

Numerical investigation of non-Ohmic hopping conduction in disordered systems

Abstract Non-Ohmic behaviour is studied in models having about 1000 sites, for the case of R-hopping. In contrast with the percolation approach, for a strong interaction with phonons, the numerical analysis predicts a decrease in the differential conductivity with increasing field, just obove the Ohmic regime. In order to study the failure of the percolation approach, the field dependence of the percolation cluster, the current cluster and the charge distribution in the model are examined.

Electric Field Dependence of Elastic Properties of TaS3

We have measured the electric field dependence of the Young's modulus and internal friction of orthorhombic Ta${\mathrm{S}}_{3}$. The modulus is observed to decrease by a few percent when the field exceeds ${\ensuremath{\epsilon}}_{T}$, the threshold for non-Ohmic conduction. At the same field, the internal friction increases rapidly, saturating at \ensuremath{\sim} 1% for fields $\ensuremath{\epsilon}>2{\ensuremath{\epsilon}}_{T}$.

Non-Ohmic Conduction and Weak Localization in 1T-TaS2

The electron localization in 1T-TaS 2 is studied by means of the analysis of the non-Ohmic conduction which is observable below liquid N 2 temperature. By correlating the electric field dependences of the conductivity, Hall coefficient and magnetoresistance with their temperature dependences it is found that an electric field has the effect of raising an electron temperature (hot-electron effect). The non-Ohmic conduction due to the electron heating mechanism is highly suggestive for the existence of the weakly localized states. The inelastic scattering length which determines the rise of the electron temperature is estimated. It shows the temperature dependence proportional to T -1/2 above 15 K, whereas it is almost T -independent below 15 K. This may possibly be interpreted as a gradual change of the mechanism of the non-Ohmic conduction associated with a crossover towards stronger localization as the temperature is lowered.

Non-ohmic conduction and weak localization in 1TTaS 2

The electron localization in 1TTaS 2 is studied by means of the non-Ohmic conduction which is observable below liq.N 2 temperature. It is found that an electric field has the effect of raising electron temperature. The non-Ohmic conduction due to the electron heating mechanism is highly suggestive for the existence of the weakly localized states in 1TTaS 2.

Non-linear conductivity of monoclinic TaS 3

Strongly non-ohmic conduction is observed in the semiconducting charge-density-wave (CDW) state of monoclinic TaS 3 above a very sharp threshold field. These features could be interpreted in terms of depinning or tunneling of pinned CDW under applied electric field. We also found that large noise appears with the onset of the non-linear conductivity and fades away as the current through the samples is increased, which behaves as the decreasing function of frequency.

Whisker Like Electrical Conduction MX3

Structural phase transitions of NbSe3 and TaS3, which are members of MX3, are reviewed. NbSe3undergoes two charge-density-weve phase tramsitions at T1=142K and T2=58K. TaS3 undergoes Peierls phase transition at 210K. Both materials show a nonohmic electrical conduction. We also review this phenomenon briefly.

Non-linear conductivity of monoclinic TaS 3

Strongly non-ohmic conduction is observed in the semiconducting charge-density-wave (CDW) state of monoclinic TaS 3 above a very sharp threshold field. These features could be interpreted in terms of depinning or tunneling of pinned CDW under applied electric field. We also found that large noise appears with the onset of the non-linear conductivity and fades away as the current through the samples is increased, which behaves as the decreasing function of frequency.

Review of the Fröhlich sliding mode in NbSe3

The anomalous transport properties of the charge-density-wave system niobium triselenide are surveyed. Early experiments on the frequency dependence and non-ohmicity of the electrical conductivity are described together with interpretations using the sliding mode mechanism. The effect of impurities, the non-ohmic Hall effect, conduction noise, and ac conduction are described. Theoretical models which have been proposed arc discussed, together with difficulties from the experimental viewpoint. Lastly, mention is made of recent experiments on NbSe3 as well as other similar systems.

Electrical Stimulation of Fabric Filtration

With zero airflow, the currents passing between parallel wires in contact with a fabric appear to be the sum of corona currents and of non-ohmic conduction currents. The origins of the latter are not clear. Wheo an aerosol is flowing, electrode currents increase with increasing air velocity. Part of this effect seems due to charges carried on the aerosol particles, and part may be due to distortion of the ion cloud by the moving air stream. Pressure-drop reduction by external electric fields generated with wire electrodes occurs in two ranges: below corona voltages there is a small dependence on applied field, while above that voltage the dependence is much steeper. It is assumed that the latter case is the result of heavier particle-charging by the ion cloud. It seems, therefore, that corona-charging of the aerosol can play an important role in reducing pressure drop by ESFF. However, another mechanism appears to operate—one which becomes apparent if fabrics with different degrees of packing density are compared. Then, the pressure-drop dependence on applied field shifts with changing packing density in a manner, that suggests the onset of additional polarization effects.

Frequency-dependent conductivity in niobium triselenide: Results and analysis

The conductivity of NbSe 3 has been measured in the Ohmic regime at frequencies up to 17 GHz. The results are compared with a model in which Frohlich conductivity arises from the heavily-damped motion of weakly-pinned charge density waves, and the increase in conductivity with frequency below 1 GHz thereby related, with partial success, to the threshold field for non-Ohmic conduction.

Electric-field depinning of charge-density waves in NbSe3

Measurements of the nonlinear conductivity in Nb${\mathrm{Se}}_{3}$ resulting from the high-temperature charge-density wave (CDW) have been made. The results show that the electronic properties of Nb${\mathrm{Se}}_{3}$ in the temperature regime where only one CDW exists are qualitatively the same as those in the the region where two CDW's coexist. In both cases a threshold field for non-Ohmic conduction and quasiperiodic noise are observed. These results rule out mechanisms for noise production which rely on the coexistence of two CDW's, such as beat phenomena. Measurements of the temperature dependence of the two threshold fields show a separate depinning of each of the two CDW's at temperatures below 59 K. No evidence for a lock-in of the two threshold fields to a common value has been seen.

Investigation of non-Ohmic hopping conduction by methods of percolation theory

Abstract Using methods of percolation theory the field dependence of the hopping conductivity is investigated. For not too high electrical fields the conductivity is shown to decrease with increasing field. This is due to segments of the first percolation paths directed oppositely to the external field. At higher fields the conductivity increases exponentially with the field. These results agree qualitatively with experimental results obtained on doped semiconductors.

Observations of negative resistance associated with superlinear emission characteristics of (Al, Ga) As double-heterostructure lasers

Observations are reported of the electrical and optical behavior exhibited by stripe-geometry, proton-bombardment-delineated, (Al, Ga)As double-heterostructure junction lasers, whose output power shows an abrupt, nearly discontinuous increase as a function of input current. When operated within this superlinear regime (in addition to exhibiting self-induced intensity pulsations) the output power averaged over many pulsations fluctuates randomly between levels corresponding to the intensities at either end of the superlinear range. A negative resistance which is light induced and associated with the lasing optical field accompanies the superlinearity, as does motion of the lasing filament along the junction plane. The low temperature behavior of the negative resistance shows that non-ohmic conduction mechanisms are present in the laser material. However, axially nonuniform changes in the luminescence observed through the substrate indicate that saturable optical absorption in the active layer at the laser mirror faces may be the predominate cause of the superlinearity and negative resistance. The development of these effects with aging may be arrested by mirror facet coatings applied before bonding.