Ultrafast Crystallization Dynamics at an Organic-Inorganic Interface Revealed in Real Time by Grazing Incidence Fast Atom Diffraction.

The poor structural properties of organic-inorganic interfaces and their variability represent the main cause of device under-performance. Understanding and controlling the development of these properties in real time has been a difficult experimental challenge. Using a recent technique based on grazing incidence fast atom diffraction (GIFAD), we were able to directly observe during deposition structural transitions in a perylene monolayer on Ag(110). Crystallization from the liquid phase occurs into two distinct structures with drastically different dynamics. Transition to the most compact packing occurs by self-organization only after a second layer has started to build up; subsequent incorporation of molecules from second to first layer triggers an ultrafast crystallization on a macroscopic sale. The final compact crystalline structure shows a long-range order and superior stability, which opens good perspectives for producing in a controlled manner highly ordered hybrid interfaces for photovoltaics and molecular electronics.