• Ashish Verma

      Articles written in Bulletin of Materials Science

    • Electrical conduction mechanism in solution grown doped polyvinyl pyrrolidone films

      P K Khare S K Paliwal R Kuraria H L Vishwakarma Ashish Verma S K Jain

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      A detailed study of electrical conduction mechanism in bimetallized ferrocene-doped polyvinyl pyrrolidone films was carried out. The measurements were carried out on films of about 20 μm thick, in the field range of (2.0–8.0) x 104 V/cm at temperatures ranging from 363 to 423 K. An investigation of the effect of impurity such as ferrocene in the polymer matrix was undertaken. Lowering of activation energy and increase in current due to doping were observed. The results showed that the charge carriers were generated by field-assisted lowering of coulombic barriers at the traps and were conducted through the bulk of the material by a hopping process between the localized states by a Jonscher-Ansari modified Poole-Frenkel mechanism. The dependence of current and activation energy on the ferrocene concentration is explained on the basis of charge transfer type of interaction between dopant and polymeric material.

    • Thermally stimulated current and electrical conduction in metal (1)-ethyl cellulose-metal (1)/(2) systems

      P K Khare Ashish Verma Sunil K Paliwal

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      Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20µm thickness have been studied as a function of electrode materials at constant poling field (5 × 104 V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks (located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied voltage in the range (2·0–5·0) × 104V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E1/2 plots are found to vary with metal work function.

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