UHV-STM studies on the structures of alkanedithiol self-assembled monolayers

The structure of alkanedithiol SAMs was investigated using an ultrahigh vacuum scanning tunneling microscope UHV-STM.. The study revealed that the monolayer film consists of fully packed striped domains with the spacing of the bright stripe lines corresponding to the length of the molecule. We also found series of separated bright dots that were attributed to sulfur atoms, indicating that the molecules are arranged with their axes almost parallel to the surface. Furthermore, we obtained STM images of the mixture SAMs formed by coadsorbed alkanethiol and alkanedithiol molecules showing a phase separated structure. The images clearly show a structural difference between the regions of alkanethiol SAMs and alkanedithiol SAMs. q1999 Elsevier Science B.V. All rights reserved