BARC/PUB/2011/1139

 
 

Charge transport in ultrathin iron-phthalocyanine thin films under high electric fields

 
     
 
Author(s)

Kumar, A.; Singh, A.; Samanta, S.; Vasundhara, K.; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.; Yakhmi, J. V.

Source

Journal of Physics-Condensed Matter, 2011. Vol. 23 (35): pp. 355801

ABSTRACT

The temperature dependent current–voltage (J–V) characteristics of 20 nm thick iron-phthalocyanine films are investigated in the temperature range of 300–30 K, and in the bias range of ±200 V. In the temperature range of 300–100 K, the charge transport is governed by bulk-limited processes with a bias dependent crossover from Ohmic (J ~ V) to exponentially distributed shallow trap mediated space–charge-limited conduction (J ~ Vα, α≥2) to space–charge-limited conduction with field enhanced mobility (ln μ ~ E1/2). However, at temperatures less than 100 K, the charge transport is electrode-limited, and undergoes a bias dependent transition from Schottky (ln J ~ V1/2) to multistep tunneling. From shallow trap mediated space–charge-limited conduction data the estimated room temperature mobility was found to be ~1.9 cm2 V-1 s-1. The high mobility of films is attributed to better structural organization due to the face-on stacking of molecules, which is supported by x-ray diffraction and UV–visible spectroscopy data.

 
 
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