Clean Electrospray Deposition of Porphyrin Molecules and Polyethylene Glycol Chains onto a Au(100) Surface

Depositing intact organic molecules with large molecular weight under ultrahigh-vacuum conditions onto a solid surface remains an important challenge in surface science, as conventional sublimation methods are often incompatible with thermally sensitive, high-mass species. Here, we demonstrate the use of a modified electrospray deposition (ESD) setup, integrated into the load-lock of an UHV chamber, to deposit porphyrin derivatives and polymerized polyethylene glycol (PEG) chains in a clean manner onto a Au(100) surface. Our experiments show that, despite the technical simplicity and absence of ion optics, the ESD setup enables preparation of clean high-quality samples, which are suitable for imaging by scanning tunneling microscopy (STM) without the need of postdeposition annealing. Detailed STM imaging at low temperatures reveals intact PEG chains with complex conformations, including folded and looped structures, which highlight the nondestructive nature of the deposition. These examples demonstrate that simple ESD methods can serve as practical and efficient alternatives to more complex ion beam systems for UHV-compatible deposition of functional molecules with a large molecular weight.