Structural investigation of monolayers prepared by deposition of (CH3S)(2) on the (111) face of single-crystal gold

Danisman M. F. , Casalis L., Bracco G., Scoles G.

JOURNAL OF PHYSICAL CHEMISTRY B, vol.106, no.45, pp.11771-11777, 2002 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 106 Issue: 45
  • Publication Date: 2002
  • Doi Number: 10.1021/jp0257911
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.11771-11777


Although self-assembled monolayers made of long chains of n-alkanethiols [CH3(CH2)(n-1)SH] on Au(111) have been extensively studied in the past, the driving forces behind the appearance of the (3 x 2root3) superlattice observed at full coverage are still not completely understood. To focus on the role played by the sulfur headgroup minimizing the interactions between chains and to prevent a possible X-ray-induced damage, we have carried out a He atom diffraction study of the adsorption of the shortest (n = 1) thiol radical, obtained by dissociative adsorption of (CH3S)(2), on the Au(111) surface. Contrary to current literature reports, domains of the hexagonal (root3 x root3)R30degrees structure are observed to convert into the well-ordered (3 x 2root3) superstructure after annealing times of a few hours. The observation of peaks forbidden by the (3 x 2root3) model proposed by Fenter et al. (Fenter, P.; Eberhardt, A.; Eisenberger, P. Science 1994, 266, 1216) suggests a distortion of the symmetry, of the unit cell. The observed chemisorption and physisorption energies were in good agreement with the literature.