A novel asymmetrically substituted dicyano-tri-tert-butylphthalocyanine ((CN)2BuPc) with rectifying behavior has been synthesized. The morphology and conductive properties of (CN)2BuPc Langmuir-Blodgett (LB) films on mica and highly ordered pyrolytic graphite (HOPG) substrates were studied by atomic force microscopy (AFM) and scanning tunneling microscopy (STM), in air at 22°C. The average area of each (CN)2BuPc molecule obtained from the AFM topography in situ is ca. 73.6 Å2, which is in good agreement with the result of ca. 74 Å2 obtained from the π-A isotherm curve of a LB film. This indicates that the molecules are standing edge-on, tilted by 38° against the surface normal of the substrate. The conductive properties for the 7-layer LB films of (CN)2BuPc were studied by STM with a tungsten tip. The asymmetric I-V curve revealed a type of rectifying behavior for a negative and a positive bias. A feature model of the intramolecular and intermolecular charge transfer is presented. It not only interprets electron transfer from electron-donor to electron-acceptor molecules via a molecular "bridge", but also the tunneling effect through intermolecular charge transfer.
|Number of pages||5|
|Journal||Advanced Functional Materials|
|Publication status||Published - 2002|