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Electrocrystallization of an Ordered Organic Monolayer: Selective Epitaxial Growth of Beta-(ET) (2)I(3) on Graphite.
Technical rept. 1 May 94-30 Jun 95,
MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
Pagination or Media Count:
We report electrochemical and in situ atomic force microscopy observations of the formation of a new class of crystalline organic monolayer, which consists of a conductive organic salt containing bisethylenedithiolo-tetrathiafulvalene ET, on highly oriented pyrolytic graphite HOPG. Growth of this monolayer accompanies the electrochemical oxidation of ET in the presence of the I3 iodine 3 anion at a freshly cleaved HOPG electrode. The monolayer covers large areas of the graphite substrate 100 square micrometers and can be removed at potentials cathodic of the ETET couple. High resolution AFM imaging of the monolayer and a 15.5 A monolayer thickness are consistent with the formation of a single 001 layer of beta-ET2I3, with the long axes of the ET molecules oriented nearly perpendicular to the graphite basal plane. The preferential formation of betaET2l3 over other polymorphs is a consequence of favorable epitaxial interactions between the overlayer lattice and that of the graphite substrate, and is manifest in selective growth of bulk betaET2l3 crystals on this electrode surface. These results demonstrate that controlled deposition of conducting mono- and multilayer films can be achieved in the presence of strong interfacial interactions during nucleation, suggesting a route to the fabrication of electronic devices based upon molecular design principles.
APPROVED FOR PUBLIC RELEASE