STRUCTURE OF SELF-ASSEMBLED DECANETHIOL ON AG(111) - A MOLECULAR RESOLUTION SCANNING-TUNNELING-MICROSCOPY STUDY

Self-assembly of decanethiol on Ag(111) is studied using ultrahigh imp edance scanning tunneling microscopy. The surface frequently shows mon atomic silver islands covering about 20% of the surface. Molecular dom ains with an average size of similar to 70 Angstrom as well as the mol ecules themselves are also imaged. From these images, three important quantities regarding the molecular structure are determined: (1) the l attice constant is 4.61 +/- 0.15 Angstrom; (2) two sets of 6-fold latt ice orientations separated by 20.7 +/- 2.3 degrees are observed; (3) f ar from domain boundaries, height variations of nearest neighbors are less than 0.1 Angstrom. A model is proposed to explain how such a stru cture could have arisen.