Charge-induced distortion and stabilization of surface transfer doped porphyrin films

The interaction between zinc-tetraphenylporphyrin (ZnTPP) and fullerenes (C-60 and C60F48) are studied using ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy (STM). Low temperature STM reveals highly ordered ZnTPP monolayers on Au(111). In contrast to C-60, a submonolayer coverage of C60F48 results in long-range disorder of the underlying single ZnTPP layer and distortion of individual ZnTPP molecules. This is induced by substantial charge transfer at the organic-organic interface, revealed by the interface energetics from UPS. However, a second layer of ZnTPP prevents C60F48 guests from breaking the self-assembled porphyrin template. This finding is important for understanding the growth behaviour of bottom-up functional nanostructures involving strong donor-acceptor heterojunctions in molecular electronics. (C) 2013 AIP Publishing LLC.