title: Modification and stability of aromatic self-assembled monolayers upon irradiation with energetic particles.
abstract: We have studied ion and electron irradiation of self-assembled monolayers (SAMs) of 2-(4'-methyl-biphenyl-4yl)-ethanethiol (BP2, CH3-C6H4C6H4CH2CH2-SH), phenyl mercaptan (PEM, C6H5CH2CH2-SH), and 4'-methyl-biphenyl-4-thiol (BP0, CH3-C6H4C6H4-SH) deposited on Au(111) substrates. Desorption of neutral particles from PEM/Au and BP2/Au was investigated using laser ionization in combination with mass spectrometry. The ion-induced damage of both BP2 and PEM SAMs is very efficient and interaction with a single ion leads to the modification of tens of molecules. This feature is the result of a desorption process caused by a chemical reaction initiated by an ion impact. Both for ions and electrons, experiments indicate that the possibility for scission of the Au-S bond strongly depends on the chemical nature of the SAM system. We attribute the possible origin of this effect to the orientation of the Au-S-C angle or adsorption sites of molecules. The analysis of electron-irradiated PEM/Au and BP2/Au, using ion-initiated laser probing, enabled measurements of the cross section for the electron-induced damage of the intact molecule or specific fragment. Analysis of electron-irradiated BP0/Au by using time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides direct evidence for the quasi-polymerization process induced by electron irradiation.
authors.affiliation: Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL 30-059 Kraków, Poland. cyganik@pc.ruhr-uni-bochum.de
authors.forename: P
authors.initials: P
authors.lastname: Cyganik
authors.forename: E
authors.initials: E
authors.lastname: Vandeweert
authors.forename: Z
authors.initials: Z
authors.lastname: Postawa
authors.forename: J
authors.initials: J
authors.lastname: Bastiaansen
authors.forename: F
authors.initials: F
authors.lastname: Vervaecke
authors.forename: P
authors.initials: P
authors.lastname: Lievens
authors.forename: R E
authors.initials: RE
authors.lastname: Silverans
authors.forename: N
authors.initials: N
authors.lastname: Winograd