Langmuir-blodgett films of charge transfer complexes of bisethylenedioxytetrathiafulvalene-alkyltetracyanoquinodimethane

Abstract

The LB films of the charge transfer complexes of oxygen-containing BEDT-TTF type donor bisethylenedioxytetrathiafulvalene (BO) and long-chain derivatives of tetracyanoquinodimethane (C nTCNQ) are prepared with and without matrix molecules. The measurements of π-A isotherm for the complex-icosanoic acid mixed system indicated the formation of mixed monolayers at the air-water interface. This was confirmed by the AFM measurements showing a granular structure of the film with the grain size of 100 nm in diameter and 3–4 nm in height. These grains are probably attributable to the BO complex. The conductivity of the LB films were strongly affected by the film-deposition method, the spreading solvent and the matrix. The mixed LB films of BO-C 10TCNQ and BO-C 14TCNQ with icosanoic acid under suitable conditions showed conductivities as high as 10 and 3 S/cm, respectively. The former LB film showed a metallic temperature dependence of conductivity down to 250 K. The conduction mechanism is discussed in terms of the film granuality.