Nucleation mechanism of TTF-TCNQ on alkali halides

Nucleation process of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) on three kinds of alkali halides is quantitatively studied by use of atomic force microscope (AFM). The sizes of the smallest nuclei observed for the TTF-TCNQ film grown on alkali halides at the substrate temperature of 20°C and the molecular flux of 1 × 1018 [molecules/m2 .s] were larger than several 10 nm. The deposition time of several ten seconds were necessary for the generation of these nuclei and that depended on the kind of substrates. The reasons why such a long period for the growth of the nuclei is necessary are discussed on basis of AFM observation.