Electron Induced Disordering and Decomposition of Alkanethiol Self-assembled Monolayers on Au(111)

Self-assembled monolayers (SAMs) are used for applications such as molecular electronics, selective deposition, and other forms of surface modification. Lithography within the semiconductor industry is adopting shorter wavelengths of light such that the interaction of secondary electrons with the organic resist is becoming the primary mechanism for photo-initiated electro-chemical reactions. To study the interaction of low energy electrons with thin organic films, measurements have been performed on electron induced disordering and decomposition of 1-decanethiol molecules grown via vapor phase deposition on Au(111). These monolayers arrange into two phases commonly referred to as lying down and standing up. The lying down phase is a physisorbed layer that is only weakly interacting with the substrate via Van der Waals forces. Conversely, the standing up phase is a chemisorbed species that is more strongly bound to the substrate. Surface analysis techniques were used to characterize the monolayers before and after electron exposure. LEED was used to determine the structure of the SAM and the rate of disordering and decomposition. TPD was used to evaluate the thermal stability of the attached SAMs and the resulting desorption products after electron exposure.