A Scanning Tunneling Microscope Study on an Ordered Mixed Monolayer of Bis(4,5-dihydronaphtho[1,2-d])-Tetrathiafulvalene and n-Tetradecane on Highly Oriented Pyrolytic Graphite

Tetrathiafulvalene (TTF) and its derivatives (TTFs) have been successfully used as building blocks to form charge transfer salts and organic semiconductors because of their special structures and rich electron nature. We report the formation of ordered mixed binary-component monolayer consisting of Bis(4,5-dihydronaphtho[1,2-d])tetrathiafulvalene (DH-TTF) and n-tetradecane (n-C₁₄H₃₀) molecules on highly oriented pyrolytic graphite (HOPG) surface. Scanning tunneling microscope (STM) imaging reveals that the two different kinds of molecules can spontaneously form ordered periodic phase separation structures on the substrate, in which ordered DH-TTF double- (or single-) lamella structures are periodically tuned by ordered n-C₁₄H₃₀ double- (or single-) lamella structures. Furthermore, scanning tunneling spectrum (STS) measurements by addressing the individual DH-TTF and n-C₁₄H₃₀ molecules in the ordered monolayer show that the two different kinds of molecules exhibit completely different I(V) characters on the HOPG substrate. The modulated arrangement of the TTF derivative by insulating molecules opens a possible route to construct organic conducting molecule ribbons for potential application in nanodevices.