Preparation and characterization of conducting thin films of molecular organic conductors (TTF-TCNQ)

Tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) form a charge-transfer complex which exhibits a high electric conductivity. In this work TTF-TCNQ thin films were prepared by CVD (chemical vapour deposition) at low pressure and using TTF and TCNQ as precursors. Substrates were common glass. These layers exhibit preferential orientation in the crystallization along the [001] direction and have a room temperature conductivity ranged between 6-24 Omega(-1) cm(-1). Whereas at low temperatures (smaller than a transition temperature T-p) they display a highly resistive semiconductor-like behaviour, above T-p the conductivity exhibits a small effective activation energy. T-p approximate to 50-60 K is interpreted as a signature of the Peierls transition. The evaluation of the stoichiometry was performed by UV-visible spectroscopy. The morphology and structure of the layers were also studied.