title: Low-energy electron induced resonant loss of aromaticity: consequences on cross-linking in terphenylthiol SAMs.
abstract: Aromatic self-assembled monolayers (SAMs) can be used as negative tone electron resists in functional surface lithographic fabrication. A dense and resistant molecular network is obtained under electron irradiation through the formation of a cross-linked network. The elementary processes and possible mechanisms involved were investigated through the response of a model aromatic SAM, p-terphenylthiol SAM, to low-energy electron (0-10 eV) irradiation. Energy loss spectra as well as vibrational excitation functions were measured using High Resolution Electron Energy Loss Spectroscopy (HREELS). A resonant electron attachment process was identified around 6 eV through associated enhanced excitation probability of the CH stretching modes ν(CH)(ph) at 378 meV. Electron irradiation at 6 eV was observed to induce a peak around 367 meV in the energy loss spectra, attributed to the formation of sp(3)-hybridized CHx groups within the SAM. This partial loss of aromaticity is interpreted to be the result of resonance formation, which relaxes by reorganization and/or CH bond dissociation mechanisms followed by radical chain reactions. These processes may also account for cross-linking induced by electron irradiation of aromatic SAMs in general.
authors.affiliation: Univ. Paris-Sud, Institut des Sciences Moléculaires d'Orsay (ISMO), UMR 8214, Orsay, F-91405, France. lionel.amiaud@u-psud.fr.
authors.forename: L
authors.initials: L
authors.lastname: Amiaud
authors.forename: J
authors.initials: J
authors.lastname: Houplin
authors.forename: M
authors.initials: M
authors.lastname: Bourdier
authors.forename: V
authors.initials: V
authors.lastname: Humblot
authors.forename: R
authors.initials: R
authors.lastname: Azria
authors.forename: C-M
authors.initials: CM
authors.lastname: Pradier
authors.forename: A
authors.initials: A
authors.lastname: Lafosse