Structural analysis of pentacene thin film growth on polycrystalline Ox-Au surfaces using scanning tunneling microscopy.

In this letter, we show the feasibility to use scanning tunneling microscopy (STM) as a stand-alone technique in analyzing the structure of organic thin films grown on polycrystalline metal surfaces. At room temperature, by effectively suppressing the molecule-substrate interaction, pentacene resumes the typical quasi layer-by-layer growth with the "thin-film phase" structure due to intermolecule interaction, while substrate roughness does not play an important role. By elevating the substrate to 320 K, two different polycrystalline phases, that is, the "thin-film phase" and the "single-crystal phase" intermixed grow and form terraced and lamellar structures, respectively. Using STM distance-voltage spectroscopy, the energy level alignment of the underlying organic/metal interfaces can also be acquired.