Scanning tunneling microscopy study of pentacene adsorption on Ag/Si(1 1 1)-(√3 × √3)R30°

Abstract The adsorption of pentacene (C 22 H 14 ) on Ag/Si(1 1 1)-(√3×√3)R30° has been investigated using ultrahigh-vacuum scanning tunneling microscopy at room temperature (RT). Three distinct phases are observed as a function of pentacene coverage. At low coverage the molecules adopt a head-to-head orientation forming a molecular row structure. At a coverage of one monolayer (1 ML), the molecules adsorb between the rows to adopt a close-packed side-by-side orientation, which is mediated by a van der Waals interaction. Higher coverage lead to a molecular reorganization which is interpreted as a tilting of the pentacene molecules from a planar to an upright configuration.