Dependent Conductivity Studies Research Articles

Temperature dependent transport properties of CuInSe2–ZnO heterostructure solar Cell

Abstract Experimental study of dc and ac transport properties of CuInSe2/ZnO heterostructure is presented. The current–voltage (I–V) and frequency dependent capacitance (C–f) characteristics of CuInSe2/ZnO heterostructure were investigated in the temperature range 160–393 K. The heterostructure showed non-ideal behavior of I–V characteristics with an ideality factor of 3.0 at room temperature. Temperature dependent dc conductivity studies exhibited Arrhenius type behavior and revealed the presence of trap level. The C−2-V plot measured at frequency 50 kHz had shown non-linear behavior. An increase in capacitance with temperature was observed. The capacitance–frequency characteristics exhibited a transition between low frequency and the high frequency capacitance. As the temperature was lowered the transition occurred at lower frequencies. The frequency and temperature dependent device capacitance had shown a defect state having activation energy of 108 meV.

Frequency dependent magnetoconductivity and conductivity study in Ni-dispersed silica nano-composite produced by sol-gel technique

The low frequency (20 Hz to 1 MHz) ac conductivity and magnetoconductivity behaviour of ceramic nanocomposite (Ni-SiO2) at low temperature down to 77 K are reported. The frequency dependent conductivity followed the power law, σ(ω) ∝ ωs. The fractional exponent s is a function of temperature and was found to increase with increasing temperature. This type of variation may be attributed to small polaron hopping. A peak present in the loss tangent indicates the presence of a Debye relaxation process. The magnetoconductivity of the samples is positive, which strongly depends on frequency. A firm theoretical explanation of frequency dependent magnetoconductivity is still lacking.

Effect of fluorine doping on structural, electrical and optical properties of ZnO thin films

We studied effect of fluorine doping on ZnO thin films prepared using chemical spray pyrolysis technique. Structural, electrical and optical characterization techniques were used for the study. Both doped and undoped films showed preferential orientation along (0 0 2) plane. Optical absorption studies indicated a decrease of energy band gap and optical transmission increased with increase in fluorine doping. PL spectrum of undoped sample has a single broad peak at 517 nm while three additional peaks appeared for fluorine-doped film. Electrical resistivity and photosensitivity decreased considerably on doping. Temperature dependent conductivity studies revealed that prominent shallow donor levels are Zn in interstitial and regular lattice positions.

Microwave assisted synthesis, characterization and humidity dependent electrical conductivity studies of perovskite oxides, Sm 1− xSr xCrO 3 (0 ≤ x ≤ 0.1)

The perovskite oxides, Sm 1− x Sr x CrO 3 (0≤ x≤0.1) were synthesized by a microwave assisted combustion route from the constituent metal nitrates and urea. The single-phase oxides were characterized by X-ray diffraction (XRD) and the lattice parameters were evaluated. The perovskite oxides were subjected to DC conductance measurements over the temperature range 100–300 °C in air atmosphere from which activation energies were determined. The current was found to increase linearly with the applied field and exponentially against temperature indicating the ohmic nature of the electrode contacts. The activation energy values for DC conductance were found to be in the range of 0.38–0.56 eV. DC resistance measurements as a function of relative humidity in the range of 5–98% RH were carried out on sintered discs at 25 °C under static conditions from which the sensitivity factor, S f ( R 5%/ R 98%) for SmCrO 3, Sm 0.95Sr 0.05CrO 3 and Sm 0.90Sr 0.10CrO 3 were calculated to be 2198, 2971, 4510, respectively. The response and recovery characteristics were studied for Sm 0.90Sr 0.10CrO 3, which exhibited good linearity and very narrow hysteresis loop.

Electrical properties of a new Ag+ ion conducting glassy system: x[0.75AgI:0.25AgCl] : (1−x)[Ag2O : P2O5

A new fast Ag+ ion conducting glassy system: x[0.75AgI:0.25AgCl]: (1−x)[Ag2O: P2O5], where 0.1 ≤ x ≤ 1 in molar weight fraction, has been synthesized by melt-quench technique using a high-speed twin roller-quencher. An alternate host salt: ‘quenched [0.75AgI: 0.25AgCl] mixed system/ solid solution’, has been used in place of the traditional host AgI. The compositional dependence conductivity studies on the glassy systems: x[0.75AgI:0.25AgCl]: (1−x)[Ag2O: P2O5] as well as xAgI: (1−x)[Ag2O: P2O5] prepared identically, indicated that the composition at x=0.75 exhibited the highest room temperature conductivity. The composition: 0.75[0.75AgI: 0.25AgCl]: 0.25[Ag2O: P2O5] has been referred to as optimum conducting composition (OCC). The study also revealed that the new/ alternate host yielded better electrolyte system. The activation energy (Ea), involved in the thermally activated conductivity process has been computed from ‘log σ − 1/T’ Arrhenius plot.

Frequency dependent conductivity and dielectric studies on RbSn 2F 5

The ac electrical data of RbSn 2F 5 are analyzed in the σ ∗(f), M ∗(f) and ε ∗(f) formalisms. The ac conductivity exhibited a power law behavior with the presence of low frequency dispersion at high temperatures. The conductivity relaxation time is determined from the maximum of the peaks of the modulus formalism associated with an activation energy of 0.56 eV, which agrees well with the dc conductivity activation energy, ΔE σ=0.55 eV, suggesting a hopping mechanism for the ionic conduction. A huge increase of the dielectric permittivity is observed at low frequency due to space charge polarization. The dielectric relaxation phenomena were detected from the peaks of the frequency dependence of the dissipation factor, tan δ. The activation energy and the relaxation time of the dielectric relaxation have been determined.

Properties of regioregular poly(3-octylthiophene)/multi-wall carbon nanotube composites

Composites films of poly (3-octylthiophene)/multi-wall carbon nanotube have been fabricated. Transmission electron microscopy revels multi-wall nanotube structures embedded in an amorphous polymer matrix. After incorporation of the nanotubes an enhancement in the electrical conductivity of up to five orders is observed. Temperature dependent conductivity studies indicate a decrease in the activation energy for the composite films. There is evidence that the composite films are much harder and much more stable than the ‘undoped’ polymer.

Conduction mechanisms in RuO2-glass composites

The electrical transport and the microstructure of RuO2-glass composites with metal oxide volume fractions 0.01 ≤ fRuO2 ≤ 0.4 have been investigated by SEM, HREM and frequency and electric field dependent conductivity studies at 4–;300 K. Different transport mechanisms controlled by the microstructure of the composite have been identified. In the limiting cases of high and low RuO2 contents metallic or ionic transport prevails. For intermediate concentrations, 0.05 ≤ fRuO2 ≤0.2, hopping and tunneling transport are superposed. Hopping transport has been identified by frequency dependent conductivity studies; evidence for tunneling transport stems from the electric field dependence of the conductivity at temperatures < 100K. The significance of the latter transport mechanisms rests on the densely packed microstructure of these composites. Under the preparation conditions involved (1100 K/15 min), predominantly RuO2 clusters with a mean size of 250 nm and comparatively short intercluster distances form within the glass matrix. As importantly, each of these clusters consists of a large number of ultrafine RuO2 particles (n > 103) separated by a uniform glass layer of ≤ 2nm thickness, i.e., the metal oxide particles remain suspended in the matrix. Based on the statistical evaluation of the SEM- and HREM-data a quantitative description of the electrical transport behaviour of RuO2-glass composites is presented.

Silver Ion Conducting Borate Glass. Evidence of Ion Association from Temperature Dependent Mobility, Conductivity, and IR Spectral Studies

AbstractThe temperature dependence of ionic mobility for a silver ion conducting borate glass with composition 55.5 AgI22.25 Ag2O22.25 B2O3 (in mol%) is reported along with conductivity. Subsequently the value of mobile carriers n is calculated. The value of n is found to decrease with increase in temperature. Two types of ion association mechanisms viz., (i) self association and (ii) network association are proposed to explain the results. The proposed ion associations are checked by optical microscopy and temperature dependent IR spectral studies.

Electrical Properties of Silver‐Doped As2S3

AbstractTemperature and frequency dependent ac conductivity studies are made for silver‐doped a‐As2S3. The temperature dependence of σac for the As2S3‐Ag system can be well explained by correlated barrier hopping model. Numerical calculations agree well with the experimental results. The energy levels and the concentration of charged defects are also estimated for these materials.

The Direct Synthesis and Characterization of Alkali Metal Hexafluorochromates (III), MI3CrF6

Abstract The reduction of an aqueous solution of CrO3 with hydrazine hydrate in the presence of an excess of equimolar amounts of MI OH and 40% HF yields green, crystalline alkali hexafluorochromates(III), MI 3CrF6 (MI= NH4, Na, K or Rb), in very high yield. The lithium analogue has been prepared by using Li2CO3 instead of lithium hydroxide. The compounds have been characterized by elemental analyses, room temperature magnetic moments, infrared spectra and molar conductivity. Time dependent molar conductivity studies of (NH4)3CrF6 and K3CrF6 suggest that the compounds do not undergo decomposition in water at ambient temperatures.