We investigate the growth of octadecylphosphonic acid (OPA) self-assembly molecules prepared by physical vapour deposition (PVD) on mica and highly oriented pyrolytic graphite (HOPG) under ultrahigh-vacuum conditions. On samples prepared by immersion from diluted solution on mica self-assembled monolayers are formed, whereas by PVD and subsequent annealing we observe the formation of almost perfect self-assembled bilayers slightly tilted with respect to the surface normal.