Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 65: Density functional theory and beyond for real materials III

O 65.3: Vortrag

Donnerstag, 25. März 2010, 11:00–11:15, H34

Atomic-level elucidation of the initial stages of self-assembled monolayer metallization — •John Keith and Timo Jacob — Universität Ulm, Albert-Einstein-Allee 47, D-89069 Ulm, Germany

Developing high performance nanotech applications and molecular electronics requires deep understanding of atomic level structural, electronic, and magnetic properties of electrode/molecular interfaces. To clarify the initial stages of interface formation during self-assembled monolayer (SAM) metallization, we used first principles density functional theory (DFT) calculations to study Pd diffusion on top of 4-mercaptopyridine (4MP)-SAMs on Au(111). After distinguishing potential energy surfaces (PESs) for different spin configurations for Pd on the SAM, we find adatom diffusion and expected Ostwald ripening is not possible over the clean 4MP-SAM surface. Pre-adsorption of Pd, however, facilitates Pd diffusion that appears to explain multiple reports on experimentally observed island and monolayer formation on top of SAMs. Furthermore, these diffusions most likely occur by moving across low-lying and intersecting PESs of different spin states. Vertical diffusion processes were also investigated, and the electrolyte was found to play a key role in preventing Pd permeation through the SAM to the substrate. Initial stages of nanoparticle formation on top of SAMs are presented, as well as their electronic structures.