Structure investigation of Ag(111)(radical7x radical7)R19 degrees -SCH3 by X-ray standing waves: a case of thiol-induced substrate reconstruction.
The structure of the Ag(111)(radical7x radical7)R19 degrees-CH3S surface phase, formed by interaction of Ag(111) with gas-phase dimethyl disulfide, (CH3S)2, has been investigated by normal-incidence X-ray standing wave (NIXSW) analysis, using (111), (11), and (200) Bragg reflections. The resulting NIXSW structural parameter values clearly exclude any simple overlayer adsorption model on an Ag unreconstructed surface. A reconstructed surface model is proposed that is consistent with the NIXSW measurements and with previous scanning tunneling microscopy results. This comprises a near-hexagonal Ag surface layer with an Ag density of only 3/7 that of the underlying substrate layers; the methanethiolate molecules are adsorbed into 3-fold coordinated hollow sites on this open layer. The results are discussed in the context of the very limited published studies of longer alkyl chain thiolates on Ag(111).
Yu
Miao
M
Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom.
Woodruff
D P
DP
Bovet
N
N
Satterley
C J
CJ
Lovelock
K
K
Jones
Robert G
RG
Dhanak
V
V