Structures of self-assembled monolayer of alkanes adsorbed on Au(111) surfaces

Citation
A. Marchenko et al., Structures of self-assembled monolayer of alkanes adsorbed on Au(111) surfaces, SURF INT AN, 30(1), 2000, pp. 167-169
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
SURFACE AND INTERFACE ANALYSIS
ISSN journal
0142-2421 → ACNP
Volume
30
Issue
1
Year of publication
2000
Pages
167 - 169
Database
ISI
SICI code
0142-2421(200008)30:1<167:SOSMOA>2.0.ZU;2-L
Abstract
The structure of self-assembled monolayers of long n-alkane molecules depos ited on an Au(111) surface has been studied by in situ scanning tunnelling microscopy at 300 K, These monolayers are formed on Au(111) either at the i nterface between gold and a solution of hexatriacontane (C36H74) in tetrade cane, or by ultrahigh vacuum (UHV) deposition of octatriacontane (C38H78). At the liquid/solid interface, the monolayer consists of a close-packed arr angement of lamellae separated by troughs. Perfect side-to-side packing of C36H74 molecules, the long axis of which stays parallel to Au [110] directi ons, forms each lamella, Lamella present two different widths (4.8 +/- 0.1 and 4.5 +/- 0.1 nm) determined by the molecular orientation with respect to troughs. In contrast, the monolayers obtained after UHV deposition at 300 K show poor organization with meandering lamellae and troughs that present strong variations in width. Nevertheless, all the C38H78 molecules stay par allel to the [110] directions of Au(111), Annealing such monolayers at 350 +/- 5 K yields a structure that looks like the one observed at the liquid/s olid interface. These results show a directional epitaxy relationship perpendicular to the [110] directions of Au(111) in a monolayer of C36H74 and C38H78 molecules. We discuss the origin of the differences observed between the molecule pack ing at the liquid/solid interface and the one in monolayers built in UHV at 300 K. Copyright (C) 2000 John Wiley & Sons, Ltd.