Preparation and properties of polycrystalline films of (TTF)(TCNQ)

Thin films of the highly conductive organic complex tetrathiofulvalinium tetracyanoquinodimethane (TTF)(TCNQ) have been prepared on a variety of substrate materials and at substrate temperatures in the range 77-310 K by thermal sublimation of bulk crystals in vacuum. Analysis of the chemical and physical structure of the films indicates that this method of film deposition yields polycrystalline (TTF)(TCNQ) with the grain size and crystalline orientation sensitively dependent on the substrate temperature. In-plane electrical conductivity of the films as a function of temperature and pressure shows behavior indicative of an appropriately weighted average of the single crystal a-axis and b-axis conductivities, with the temperature dependence above the metal-insulator transition temperature influenced by a weakly activated process attributed to crystalline grain boundaries. Comparison of our results with those for sublimation of 1:1 mixtures of TTF with TCNQ suggests that (TTF)(TCNQ) vaporizes primarily as a complex rather than as the individual neutral components. © 1975.