Thermal annealing of the preassembled films favored well-packed, large molecular domains that were studied in real space with unprecedented detail and accuracy. At room temperature the system has several stable molecular conformations, which implies that chemisorption energies balance the energy of interaction between molecular chains. Our results contribute to a longstanding scientific debate on the structure of self-assembled monolayers and provide the basis for an improved understanding of organic interfaces.
Domains differ by their phase, their chain tilt, or the origin of sulfur adsorption.
Molecular arrangements are hexagonal with an additional rectangular superlattice. The phases originate from the particular distribution in the unit cell of molecules with different twist angles that move end groups at different height levels in and out of the average plane of the monolayer by 0.03 nm.