Structural manipulation of ultrathin organic films on metal surfaces: the case of decane thiol/Au(111)

Monomolecular films of decane thiol ([CH3(CH2)(9)]SH) have been adsorbed on Au(111) single crystals both via vacuum deposition and from an ethanolic solution. The epitaxial structure of the ultrathin organic films has been identified at room temperature via low-energy electron diffraction to be c(4 root 3 x 2 root)3)R30 degrees for the solution grown film and rectangular c(23 x root 3) for the vacuum deposited film. These structures correspond to molecules adsorbed on the surface with their carbon chains flat on the surface (vacuum deposited) and nearly perpendicular (solution grown). It is demonstrated that this orientation can be changed reversibly in vacuum via either annealing the films or exposing them to additional gas.