AVS 56th International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF1-TuA

Paper TF1-TuA11
Tuning Knobs for the Morphology and Dewetting of a Bimodal Molecular System

Tuesday, November 10, 2009, 5:20 pm, Room B3

Session: Computational Modeling and Analysis of Thin Films
Presenter: J. Topple, McGill University, Canada
Authors: J. Topple, McGill University, Canada
S. Burke, UC Berkeley
S. Fostner, McGill University, Canada
P. Grutter, McGill University, Canada
Correspondent: Click to Email
The interesting optical and electronic properties of certain organic molecules have led to their use in a range of organic electronic and optoelectronic applications. The morphology of thin films critically determines application relevant properties, and can be controlled during growth to some degree by experimental parameters. However, post-growth dynamics may change the film structure and resulting properties. We explore methods of tuning film morphology and the rate of dewetting through coverage, surface templating and temperature control. Non-contact atomic force microscopy (NC-AFM) is a non-destructive, high resolution scanning probe technique that can be applied to non-conductive surfaces. Perylene derivatives have been studied as prototypal organic semiconductors for use in electronic applications. Deposition of sub-monolayer coverages of 3,4,9,10-perylenetetracarboxylic diimide onto NaCl (001) at room temperature results in the bimodal growth of coexisting square and needle shaped islands. The epitaxy of each island type was determined from molecular and atomic resolution NC-AFM images. Post-deposition, the stable needle islands grow while the metastable square islands disappear completely within days. This is characterized as a dewetting transition, the dynamics of which have been described and empirically fit to the monomolecular growth model. The resultant island distribution, size, and rate of dewetting may be tuned by templating the NaCl substrate with single atomic layer deep pits, depositing gold nanoclusters, or a combination of the two to modify island nucleation. The diffusion lengths may be altered by varying the substrate temperature. This characterization is an important step in controlling the structure of thin organic films for nanoscale devices which are sensitive to the nanoscale film structure.