Preparations and Evaluations of C_(60) Thin Films for Organic Field-Effect Transistors

摘要

Fullerene C_(60) thin films were grown on a mica top-gate-type substrate and on a CaF_2 // Si(111) bottom-gate-type substrate with the aim of fabricating high-performance organic field-effect transistors (FETs). It is expected that single-crystal C_(60) thin films with a large grain have a high mobility as n-type materials because of the lack of a potential barrier at the grain boundaries for conducting electrons. On both substrates, oriented _(60) films were obtained. In particular, on the mica substrate, the highly oriented films had grains larger than 1 x 1 μm and a two-dimensionally flat surface with 60 and 120 deg facets. The step height was 0.8 nm, consistent with that of an hcp bulk structure. The highly oriented films were grown at the substrate temperature at which the C_(60) molecules at the tips of spiral grains re-evaporated. The obtained single-crystal _(60) thin films with large grains are promising for high-performance organic FETs.