Melting Point Enhancement of a Self-Assembled Monolayer Induced by a van-der-Waals-Bound Capping Layer

For phase transitions in complex low-dimensional organic materials, the internal degrees of freedom of the molecules, which are an important characteristic of organics, have to be considered, and a very rich phase behavior, as seen, for example, in Langmuir films (on liquid surfaces) can be found. Among the well-defined, crystalline two-dimensional organic thin films chemisorbed on a solid substrate, self-assembled monolayers (SAMs) are probably the best characterized systems, and the phase behavior of the archetypal SAM system (alkanethiols on Au(111)) as a function of coverage and temperature has been thoroughly studied.