Adsorption of substituted pyrrolidone molecules on Au(111): an STM and XPSstudy

The adsorption of several molecules with a pyrrolidone ring (triacontane-py rrolidone (NTP), 2-pyrrolidone (Py) and methyl-2-pyrrolidone (Mpy)) on an A u(111) surface has been studied by scanning tunnelling microscopy (STM) and by XPS, Self-assembled monolayers have been observed only for NTP and Py m olecules, whereas STM images show a disordered Mpy overlayer. The XPS measu rements on Py and Mpy monolayers reveal that the nitrogen atom of the pyrro lidone group is involved in different chemical bonds, depending on the mole cule. Considering both STM and XPS data, models of molecule packing are pro posed. Finally, tacking advantage of the different locations of the pyrroli done function in these monolayers, we discuss the parameters that govern th e presence of the pyrrolidone group in STM images, Copyright (C) 2000 John Wiley & Sons, Ltd.