title: UPS, XPS, and NEXAFS study of self-assembly of standing 1,4-benzenedimethanethiol SAMs on gold.
abstract: We report a study of the self-assembly of 1,4-benzenedimethanethiol monolayers on gold formed in n-hexane solution held at 60 °C for 30 min and in dark conditions. The valence band characteristics, the thickness of the layer, and the orientation of the molecules were analyzed at a synchrotron using high resolution photoelectron spectroscopy and near edge X-ray adsorption spectroscopy. These measurements unambiguously attest the formation of a single layer with molecules arranged in the upright position and presenting a free -SH group at the outer interface. Near edge X-ray absorption fine structure (NEXAFS) measurements suggest that the molecular axis is oriented at 24° with respect to the surface normal. In addition, valence band features could be successfully associated to specific molecular orbital contributions thanks to the comparison with theoretically calculated density of states projected on the different molecular units.
authors.affiliation: Dipartimento di Ingegneria dei Materiali e dell'Ambiente, Università di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Pasquali
authors.forename: Fabio
authors.initials: F
authors.lastname: Terzi
authors.forename: Renato
authors.initials: R
authors.lastname: Seeber
authors.forename: Stefano
authors.initials: S
authors.lastname: Nannarone
authors.forename: Debasish
authors.initials: D
authors.lastname: Datta
authors.forename: Céline
authors.initials: C
authors.lastname: Dablemont
authors.forename: Hicham
authors.initials: H
authors.lastname: Hamoudi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Canepa
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Esaulov