REAL-SPACE OBSERVATION OF NANOSCALE MOLECULAR DOMAINS IN SELF-ASSEMBLED MONOLAYERS

Scanning tunneling microscopy with very high gap impedance reveals sev eral stable molecular conformations of organic monolayers self-assembl ed from alkanethiols on gold. Thermal annealing of the preassembled fi lms favored well-packed large molecular domains that were studied in r eal space with unprecedented detail and accuracy. At room temperature the system has several stable molecular conformations, which implies t hat chemisorption energies balance the energy of interaction between m olecular chains. A similar probability of different conformations indi cates almost equal total energies, which makes it an interesting-and c hallenging-object for molecular dynamics simulations. Our results cont ribute to a long-standing scientific debate on the structure of self-a ssembled monolayers and provide the basis for an improved understandin g of organic interfaces.