• Ahmet Altindal

Articles written in Bulletin of Materials Science

• A.c. and d.c. conduction processes in octakis[(4-tert-butylbenzylthio)-porphyrazinato]Cu(II) thin films with gold electrodes

The d.c. and a.c. electrical transport properties of Au/Pz/Au devices with various thickness of Pz(octakis[(4-tert-butylbenzylthio)-porphyrazinato]Cu(II)) layer have been investigated. Measurements revealed that, in contrast to previously investigated Au/Pc/Au structures, low voltage d.c. behaviour of the films can be described by the field-lowering mechanisms with a $\log$(𝐽) ∝ 𝑉1/2 current density-voltage characteristics under forward and reverse bias. For high reverse voltages, the observed ln (𝐽/𝑉2) - 1/𝑉 characteristics indicated that the origin of conduction mechanism is Fowler–Nordheim tunnelling (FNT). On the other hand, the voltage dependence of current density at the higher forward-voltage region indicates that the mechanism of conduction in Au/Pz/Au devices is space charge limited conduction dominated by exponential trap distribution. A thickness independent barrier height was observed for tunnelling, while the total trap concentration show a general tendency to decrease with increasing film thickness. The a.c. conductivity showed two regions in the ln (𝜎a.c.) - ln(𝑓) plots having different slopes, leading to the conclusion that for low frequency region, the dominant conduction mechanism is a small polaron tunnelling at all temperatures, whereas for high frequency region, correlated barrier hopping model is the dominant mechanism in the investigated devices.

• Beta irradiation effects on impedance spectra of electrospun PEDOT:PSS nanofibres

Poly(3,4-ethylenedioxythio-phene):poly(styrenesulphonate) (PEDOT:PSS) nanofibres were first prepared via electrospinning method. Microstructural arrangement of the nanofibres was investigated by scanning electron microscopy technique. Then, the effect of beta irradiation with different absorbed doses on their impedance spectra were investigated in the frequency range from 5 to 13 ${\times}$ 10$^6$. It was observed that beta irradiation leads to a considerable decrease in both real and imaginary parts of the complex dielectric function, and alternating current conductivity of the nanofibres. The obtained frequency dependent conductivity data were discussed in terms of pair approximation. It was established that, for all beta irradiation doses, the frequency dependence of the conductivity is characterized by the presence of four frequency regions with different slopes. Analysis of the impedance data revealed that chain scission via chain cross-linking and free radical formation are most likely mechanisms for changes in impedance parameters. Two clear semicircles in Nyquist plot have been successfully explained by employing two parallel R-CPE equivalent circuits in series configuration. An overall evaluation of the obtained data indicates that electrospun PEDOT:PSS nanofibres have great potential for the development of highly sensitive impedance-based beta radiation sensor.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020