  The self-assembly of molecules at surfaces can be caused by a range of
physical mechanisms. Assembly can be driven by intermolecular forces, or
molecule-surface forces, or both; it can result in structures that are in
equilibrium or that are kinetically trapped. Here we review examples of
self-assembly at surfaces that have been studied within the User program of the
Molecular Foundry at Lawrence Berkeley National Laboratory, focusing on a
physical understanding of what causes patterns seen in experiment. Some
apparently disparate systems can be described in similar physical terms,
indicating that simple factors -- such as the geometry and energy scale of
intermolecular binding -- are key to understanding the self-assembly of those
systems.
