An Epitaxial Organic Film. The Self-Assembled Monolayer of Docosanoic Acid on Silver (111)

Abstract

Docosanoic acid in solution spontaneously forms an ordered self-assembled (SA) monolayer on the silver(111) surface, exposing methyl groups to the atmosphere. The contact wetting angles for water and hexadecane are 116° and 55°, respectively. Surface X-ray diffraction shows that the in-plane structure of the SA monolayer is p(2×2). The SA monolayer is present in domains of about 215 Å with a mosaic spread of 0.85°. The chains within the monolayer are tilted at 27 ± 1° from the surface normal toward the near neighbors. We conclude that the carboxylate group is bound nearly normal to specific sites on the Ag surface and that this determines the interchain spacing. The tilt angle is a consequence of this interchain spacing. © 1993, American Chemical Society. All rights reserved.