Structure of self-assembled monolayers of short alkylthiolates on Au(111) and Ag(111)

P. N. ABUFAGER; J. SOLANO CANCHAYA; Y. WANG; L. ALVAREZ SORIA; M. ALCAMÍ; F. MARTÍN; K. REUTER; M. L. MARTIARENA; H. F. BUSNENGO

Bordeaux

Conferencia; Elementary Reactive Processes at surfaces; 2010

We present a comparative study of the relative stability of various structures of high coverage (standing-up) self-assembled mono-layers (SAMs) [1] of alkylthiolates  on Ag(111) and Au(111) based on: i) Density Functional Theory (DFT) calculations to evaluate the S-substrate interaction and ii) a chain-chain interaction potential, recently derived from second order Møller-Plesset (MP2) calculations for alkanethiols in gas phase [2]. For both substrates we consider the two possible surface coverages observed experimentally for Ag(111) and Au(111): i.e. 3/7 and 1/3 respectively. For methylthiolate/Ag(111), we report a new possible structure for coverage 3/7, involving top-most layer surface Ag atom vacancies (more stable than the most stable one found so far, corresponding to the unreconstructed surface) characterized by various structural parameters in excellentagreement with experiments [3]. Our calculations successfully account for the coverage observed for the shortest chain alkylthiolates as well as the experimental tilt angle of longer chain alkylthiolates on both substrates [1].References[1] Love J. C., Estroff L. A., Kriebel J. K., Nuzzo R. G., and Whitesides G. M., Chem. Rev. (2005), 105, 1103;Vericat C., Vela M. E., Gago J. A. M., Torrelles X., andSalvarezza R. C., J. Phys.: Condens. Matter (2006), 18,R867; Woodruff D. P., Phys. Chem. Chem. Phys. (2008), 10, 7211.[2] Solano Canchaya J. G., Wang Y., Alcamí M., Martín F. and Busnengo H. F., Phys. Chem. Chem. Phys.(2010), 12, 7555.[3] Abufager P.N., Alvarez Soria L., Martiarena M.L., Reuter K., and Busnengo H.F. (submitted).