Structure of mercaptoalcohol self-assembled monolayers on Au(111)

Structures of mercaptoalcohols (1-mercaptohexanol: C6OH, 1-mercaptobutanol: C4OH and 1-mercaptopropanol: C3OH) were studied with scanning tunneling microscopy (STM) and density functional theorem (DFT) calculations. Three structures were observed depending on the exposure of mercaptoalcohols: the striped structure (stripe A), at low exposure, with the stripe distances of 2.30 +/- 0.07nm (8a(0)) for C6OH, 1.73 +/- 0.05 nm (6a(0)) for C4OH, and 1.44 +/- 0.04 nm (5a(0)) for C3OH; the stripe structure (stripe B), at high exposure, with the stripe distances of 1.19 +/- 0.04 nm (4a(0)) for C6OH and 1.01 +/- 0.03 nm (3.5a(0)) for C4OH; and the randomly distributed cluster-like structures at the highest exposure. Stripe B was not observed for C3OH. A (root 3 x root 3)R30 degrees related structure, which is the highest coverage structure for alkanethiols on Au(1 1 1), was not observed. The structures are uniquely determined by the formation of hydrogen bonding. (c) 2004 Published by Elsevier B.V.