Adsorption and desorption processes of self-assembled monolayers of hexanethiol on Au (111) were studied by scanning tunneling microscopy (STM). The STM study showed the coexistence of two domain structures, (√3 × √3)R30° and c(4×2) superlattice, from hexanethiol SAMs on Au(111) formed after 1 day deposition. This result can be attributed to different adsorbed states of thiol molecule on Au(111) such as thiol monomer and dimer. The new c(4×2) superlattice which shows three different height modulations of symmetry-inequivalent molecules having a hexagonal packed structure to the surface was observed from hexanethiol SAMs after desorption of thiol molecules in diethyl ether. The STM study reveals that desorption of molecules starts from domain boundaries and around etch pits, and forms missing-rows in highly packed regions. The c(4×2) superlattice as two-dimensional domain structure could be observed from SAM films prepared after a longer deposition or desorption time more than 1 day. Transformation of domain structure from (√3 × √3)R30° and c(4×2) superlattice might have closely related to the dimerization of adsorbed thiol on gold during SAM growth. This result would support the previous report by Mohri et al. [Langmuir, 11, 1612 (1995)]. They found that 4-aminobenzenethiol (monomer) on the surface of gold powder is spontaneously changed to 4,4′-diaminophenol disulfide (dimer) in ethanol using UV and FTIR measurements.
|Number of pages||5|
|Journal||Korea Polymer Journal|
|Publication status||Published - 1998 Dec 1|
ASJC Scopus subject areas
- Chemistry (miscellaneous)
- Polymers and Plastics