Ion-induced erosion of organic self-assembled monolayers

Laser post-ionization mass spectrometry combined with Scanning Tunneling Mi croscopy (STM) has been used to investigate processes of ion-stimulated ero sion of self-assembled monolayers (SAM) of phenethyl mercaptan C6H5CH2CH2S (PEM) deposited on gold. Results indicate that only PEM fragments are emitt ed from the surface. Most of the PEM fragments (predominantly C6H5CH2CH3 wi th m/z = 106) are emitted with thermal kinetic energies. STM images collect ed on 8 keV H-2(-)-irradiated surfaces with a system tuned to probe electro nic states of sulfur atoms show no additional damage induced by irradiation . This indicates that sulfur atoms are not removed from the surface during hydrogen bombardment. It is proposed that the emission of SAM molecules is initiated by chemical reactions which gently break C-S bonds. (C) 1999 Else vier Science B.V. All rights reserved.