Molecular ordering of organosulfur compounds on Au(111) and Au(100): Adsorption from solution and in ultrahigh vacuum

• DOI: 10.1063/1.464613
• Publication Date: 2002-07-26T12:22:38Z
• Authors: Lawrence H. Dubois; Bernard R. Zegarski; Ralph G. Nuzzo
• Keywords: Overlayer; Organosulfur compounds; Low-energy electron diffraction; Alkane

Low-energy electron diffraction and reflection-absorption infrared spectroscopy were used to study the monolayers formed by adsorption of n-alkane thiols [HS(CH2)mCH3] on both (111) (100) single-crystal gold substrates. Samples prepared dosing either from solution (m=15, 17, 18, 21) or in ultrahigh vacuum (m=0–9). On Au(111), ordered surface structures are obtained which can be indexed as (n√3×√3)R30°, where n varies 1 6. Au(100), short chain leads formation a c(2×2) overlayer while longer homologs show additional spot splittings. It is also found that length influences character seen perturbs reactive sticking probability molecules dosed UHV. Infrared studies reveal polymethylene chains Au(100) comprised nearly all-trans conformations less canted than comparable Au(111). A simple model proposed account for differences two surfaces mechanism assembly organic into monolayer phases presented.