M. Ghosh

Electron transport properties of cobalt doped polyaniline

Electrical transport properties of cobalt doped polyaniline in an aqueous ethanol medium were investigated in the temperature range 77 ≤ T ≤ 300u2009K, applying magnetic fields up to 1u2009T in the frequency range 20u2009Hz–1u2009MHz. The room temperature dc resistivity increases with increase in Co content. The dc resistivity and magnetoresistivity of these samples have been interpreted in terms of the variable range hopping theory. The frequency dependence of conductivity has been described by a power law σ(ω) ∝ ωS. The value of s is found to be temperature dependent, which shows a decreasing trend with temperature. The correlated barrier hopping model is the most likely mechanism for the electron transport. The different physical parameters were calculated from the experimental data.

Electrical resistivity of titanium nitride thin films prepared by ion beam-assisted deposition

Abstract We report the electrical resistivity of titanium nitride thin films prepared by ion beam-assisted deposition technique in the temperature range 77⩽ T ⩽300xa0K. The residual resistivity ( ρ 0 ) of the films decreases by increasing nitrogen partial pressure. The films show the quadratic temperature behavior of resistivity in the investigated temperature range. Attempt has been made to explain such anomalous behavior by using existing theories.

Low temperature transport properties of Cl-doped conducting polyaniline

Abstract A study on the electron transport property based on the measurement of the electrical conductivity of HCl doped conducting polyaniline both in the presence as well as in absence of magnetic field has been made in the temperature range of 1.8 K ≤T≤300 K . The conductivity of the samples has been observed to show an increasing trend with increasing temperature. The conductivity ratio [r=σ(300 K )/σ(1.8 K )] is large for the sample having higher dopant concentration. A transition from Mott (T1/4) to Efros–Shklovskii (ES) (T1/2) in the temperature dependent conductivity has been observed at 10xa0K. The electrical conductivity obeys T3/4 law in presence of magnetic field. Such parameters as density of states, molecular vibrational frequency, hopping distance and localization length have been determined from the plot of conductivity versus temperature.

Alternate and direct current conductivity of conducting polyaniline dispersed with poly vinyl alcohol and blended with methyl cellulose

The electrical conductivity, both dc and ac, of conducting polyanilline dispersed with poly vinyl alcohol and blended with methyl cellulose has been investigated in the temperature range of 77⩽T⩽300K and in the frequency range 20 Hz to 1 MHz. The dc conductivity does not obey the standard variable range hopping model, but it satisfies hopping transport between the superlocalized states of polymer. The frequency dependence of conductivity has been described by the power law, σ(ω)αωs. The variation of “s” with temperature suggests that the ac conduction is due to the correlated barrier hopping. Temperature and frequency dependent dielectric constant indicates the Debye-type dispersion.

Frequency dependent conductivity of aluminium nitride films prepared by ion beam-assisted deposition

Abstract The frequency dependent conductivity of different thin AlN films measured in the frequency range 10 Hz to 2 MHz for temperature between 300 and 573 K is reported. It is observed from the experimental data that the AC conductivity in the AlN thin films is proportional to ωs. The value of s is found to be temperature dependent, which shows a decreasing trend with temperature. The correlated barrier hopping model is the most likely mechanism for the electron transport. The polaron binding energy (Wm), the height of Coulomb barrier (W), and the characteristic relaxation time (τ0) have been calculated.

Frequency Dependent Conductivity of Thin ZnO Films Prepared by R.F. Sputtering Technique

AC conductivity of different thin zinc oxide films measured in the frequency range of 10 Hz to 2 MHz in the temperature interval of 300 K to 575 K is reported. ZnO films were prepared by reactive r.f. magnetron sputtering from ZnO target. The experimental data reveal that a.c. conductivity is proportional to ωs. The value of s was found to be temperature dependent, decreases with increasing temperature. These observations suggest that correlated barrier hopping model is the most likely mechanism. The temperature dependence of a.c. Conductivity is expressed in power law form as σ(ω) ∝Tn. The temperature exponent n is found to be increasing with increasing temperature and decreasing frequency in accordance with the narrow band limit. At high temperature the conductivity variation with frequency is comparatively small. The polaron binding energy (Wm), the height of Coulomb barrier (W) and the characteristic relaxation time (τ0) have been calculated. The values of Wm and W increase as the thickness decreases whereas the values of τ0 decrease with decreasing thickness.

Low temperature electrical conductivity and magnetoconductivity of Fe39Ni39Mo4Si6B12 and Co58Ni10Fe5Si11B16 metallic glass alloys

A detailed study on the weak localization phenomenon vis-a-vis electron-electron interaction effects in magnetic metallic glasses has been carried out. We measured the electrical conductivity and magnetoconductivity within the temperature range 1.8≤T≤300K. A maximum on the conductivity versus temperature curve exists atT=Tm. The conductivity was observed to follow aT1/2 law forTTm. Magnetoconductivity data of these alloys indicate the prominence of electron-electron interaction at low temperatures. The authors have determined the inelastic scattering field and spin-orbit scattering field from the magnetoconductivity data. The inelastic scattering field obeys aTp law (p=2) at low temperatures.

Transport properties of Ti3Ir compound at low temperature

Electrical resistivity and magnetoresistivity of Ti3Ir compound have been measured in the temperature range 2.0 K ≤T ≤ 300 K in absence as well as in presence of magnetic field upto 7.7 T. The low temperature resistivity shows aT2 behaviour whereas the high temperature resistivity shows a linear behaviour. The magnetoresistivity is positive and cannot be explained by simple s-d scattering model. The enhancement of the coefficient A of theT2 term and the deviation from the quadratic field dependence of the resistivity may be due to the anisotropy in the compound.