Abstract
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(σ a.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.
Original language | English |
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Pages (from-to) | 461-468 |
Number of pages | 8 |
Journal | Bulletin of Materials Science |
Volume | 37 |
Issue number | 3 |
DOIs | |
Publication status | Published - May 2014 |
Externally published | Yes |
Funding
This work was supported by the Yıldız Technical University Commission of Scientific Research Projects under Grant No. 2012-01-01-KAP04. Authors are thankful to the Scientific Research Commission of Yıldız Technical University.
Funders | Funder number |
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Yıldız Technical University Commission of Scientific Research Projects | 2012-01-01-KAP04 |
Keywords
- A.c. conductivity
- Correlated barrier hopping
- Porphyrazine
- Spin coating
- Tunnelling