AVS 56th International Symposium & Exhibition
    Surface Science Thursday Sessions
       Session SS2-ThA

Paper SS2-ThA2
The Directed Assembly of TiOPc - C60 Films: Three Structural Motifs

Thursday, November 12, 2009, 2:20 pm, Room N

Session: Supramolecular Interfaces by Design
Presenter: Y. Wei, University of Maryland
Authors: Y. Wei, University of Maryland
S. Robey, National Institute of Standards and Technology
J. Reutt-Robey, University of Maryland
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A key strategy for the improvement of organic electronic devices involves the optimization of chemical morphology on the interfaces of donor-acceptor heterojunctions for efficient charge separation. Fundamental studies of chemical morphology - electronic property relations, particularly along crucial domain boundaries, are needed to realize these goals. We present STM/STS studies of TiOPc: C60 films, prepared in three dramatically different structural motifs: (1) Nanophase segregated TiOPc and C60 domains, (2) A co-crystalline TiOPc (2) C60 (1) honeycomb network and (3) A regular array of triangular TiOPc domains and C60 nanoclusters with a 10 nm repeat. Motif selection is accomplished through anisotropic TiOPc-TiOPc interactions, under the process control of TiOPc deposition rates. Subsequent C60 deposition on these pre-engineered TiOPc films yields these three distinct structural motifs. Chemical morphology-electronic relations are then determined via Z (V) STS spectroscopy. Electronic transport gaps vary weakly (~0.2 eV) by C60-TiOPc phase. Significantly, an ~0.5 eV increase in the transport gap appears along heterointerface boundaries. We present structural models for each hetero interface and discuss the physical origin of the observed transport characteristics.

This work has been supported by the National Science Foundation under Surface Analytical Chemistry grant CHE0750203 and the Dept. of Commerce through the NIST small grants program.