TCBG Seminar

Disorder and phase transition phenomena in thin films of organic charge transfer compounds

Vita Solovyeva
Physikalisches Institut, Goethe Universit├Ąt,
Dept. Physics, University of Frankfurt
Frankfurt, Germany

Friday, April 29, 2011
3:00 pm (CT)
3269 Beckman Institute


Organic charge transfer compounds represent a class of materials for interdisciplinary research on the interface of correlation physics, material science and chemistry. It is the basis for exploration in the rapidly evolving field of organic electronics. In this context the investigation of organic thin films becomes increasingly important [1-3]. We performed a systematic study of thin films and microcrystals of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane), see figure below, which is a quasi-one- dimensional organic metal. TTF-TCNQ single crystals show metallic behavior down to about 60 K and undergo a series of phase transitions at TH=54 K, TI=49 K and TL=38 K, which successively suppress the metallic conductivity of the TTF and TCNQ chains, turning the material into an insulator. The phase transition at 54 K is driven by a charge density wave (CDW) instability in the TCNQ chains and is usually referred to as Peierls transition. The transport properties of TTF-TCNQ thin films and microcrystals are different from those in single crystals, where the difference stems from the growth arrangement, defects and disorder in the material. We have studied this difference by investigating the influence of critical parameters such as substrate materials, growth temperature, induced strain and electron irradiation on Peierls phase transition [4,5].

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