Theory of nanoscale atomic lithography. An ab initio study of the interaction of "cold" Cs atoms with organthiols self-assembled monolayers on Au(111).

This paper deals with the microscopic mechanism of nanolithography of self-assembled monolayers (SAM) of alkanethiol molecules on Au(111) induced by the exposure of the film to a beam of "cold" Cs atoms. Density functional theory calculations have been carried out to elucidate the mechanism of interaction of the Cs atoms with the SAM. We found that the film damage occurs in two steps: the Cs atom penetrates the SAM and at a distance of 10-12 Angstrom from the surface donates one electron to Au, forming a Cs(+) cation which binds strongly to the surface and interacts with the polar head of the SR molecule. The thermal energy released in this process largely exceeds the energy required to stimulate the desorption of RS-SR disulfide molecules from the Au surface with consequent damage of the film. No chemical interaction occurs between Cs or Cs(+) and the hydrocarbon chain of the thiol molecule.