Influence of steps on the tilting and adsorption dynamics of ordered Pn films on vicinal Ag(111) surfaces

Here we present a structural study of pentacene (Pn) thin films on vicinal Ag(111) surfaces by He atom diffraction measurements and density functional theory (DFT) calculations supplemented with van der Waals (vdW) interactions. Our He atom diffraction results suggest initial adsorption at the step edges evidenced by initial slow specular reflection intensity decay rate as a function of Pn deposition time. In parallel with the experimental findings, our DFT+vdW calculations predict the step edges as the most stable adsorption site on the surface. An isolated molecule adsorbs as tilted on the step edge with a binding energy of 1.4 eV. In addition, a complete monolayer (ML) with pentacenes flat on the terraces and tilted only at the step edges is found to be more stable than one with all lying flat or tilted molecules, which in turn influences multilayers. Hence our results suggest that step edges can trap Pn molecules and act as nucleation sites for the growth of ordered thin films with a crystal structure similar to that of bulk Pn.Comment: 4 pages, 4 figures, 1 tabl

Highly Ordered Assembly of Single-Domain Dichloropentacene over Large Areas on Vicinal Gold Surfaces

Defining pathways to assemble long-range-ordered 2D nanostructures of specifically designed organic molecules Is required In order to optimize the performance of organic thin-film electronic devices. We report on the rapid fabrication of a nearly perfect self assembled monolayer (SAM) composed of a single domain 6,13-dichloropentacene (DCP) brick wall pattern on Au(788). Scanning tunneling microscopy (STM) results show the well-ordered DCP SAM extends over hundreds of nanometers. Combining STM results with insights from density functional theory, we propose that a combination of unique Intermolecular and molecule-step interactions drives the DCP SAM formation

Impact of fluorination on initial growth and stability of pentacene on Cu(111)

Structure, growth, thermal stability, and electronic properties of thin films of the fully fluorinated analogue to the archetypical organic semiconductor pentacene (PEN), perfluoropentacene (PFP), were investigated on Cu(111) at room temperature by scanning tunneling microscopy (STM), low energy electron diffraction (LEED), ultraviolet photoelectron spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS). In contrast to PEN, where molecules could only be imaged by STM at full monolayer coverage, PFP was seen to stabilize in disordered clusters already in the submonolayer regime. Furthermore, while long-range order was observed for closed PEN molecular monolayers, PFP only formed a disordered first wetting layer. Highly ordered domains were not observed until the formation of the second layer of PFP. In this layer, the molecular planes are inclined to the surface, as supported by additional STM measurements on graphite and theoretical modeling. Careful consideration of the structural details in the transitional growth regime from molecular mono- to multilayers thus emerges as the key ingredient to achieving a deeper understanding of metal/organic interfaces relevant for organic electronic devices