Recovery of self-assembled monolayer on Au(111)

Self-assembled monolayers (SAMs) on Au(111) were formed in vacuum by depositing nonanethiol molecules on a gold substrate, and the resultant film was observed and modified using a scanning tunneling microscope (STM). The application of voltage pulses of 2.6 V to the sample resulted in the local extraction of molecules from the film without causing serious damage to the substrate and the molecules. The dynamic reformation process of the SAM film after the molecular extraction was observed. An uncovered area of about 10 nm(2) was almost recovered typically within several minutes, and the molecular lattice was once again visible. This recovery process was suppressed during the period when the STM tip was detached from the film surface, indicating that the extracted molecules were transferred to the tip surface, and that they returned as the tip scanned over the uncovered area. A small number of defects that did not disappear were detected, suggesting that molecular readsorption was prevented on the sites. (C) 1999 Elsevier Science B.V. All rights reserved.