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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 22, Number 2
BKCSDE 22(2)
February 20, 2001 

STM Study of 2-Mercaptoethanol Self-Assembled Monolayer on Au(111)
Moonsup Hyun, Choong Kyun Rhee
Self-assembled monolayer (SAM), 2-Mercaptoethanol, Au(111), Scanning tunneling microscope (STM).
Presented are the STM images of self-assembled monolayer of 2-mercaptoethanol on Au(111). Striped structures of (6X 3½), (5X 3½), (4X 3½) and compact-(5X 3½) were observed after annealing at 80℃. Analysis of the ordered structures revealed that the basic fundamental units of the ordered structures were three crystallographically non-equivalent (3½ X 3½)R30° assemblies, and that the way of combination of the assemblies produced the four different structures. The (6X 3½) structure ( θ = 0.33) was composed of one (3½ X 3½)R30° assembly, while the (5X 3½) ( θ = 0.30) and (4X 3½) ( θ = 0.38) structures were consisted of two (3½ X 3½) R30° assemblies, separated by 5a and 4a, respectively. Furthermore, the compact-(5X 3½) structure ( θ = 0.50) was obtained by overlapping three (3½ X 3½)R30° assemblies. In spite of the diversity in the adsorption structures, all the adsorption sites of 2-mercaptoethanol were fundamentally identical. On the other hand, the unannealed primitive SAM of 2-mercaptoethanol was characterized by two observations: a short-range order keeping the adsorbed molecules at approximately 3½ a and the small domains of the striped structures supporting that the observed surface structures on the annealed surface were the extension of the primitive layer of 2-mercaptoethanol. Comparing these observations with the already published structures of ethanthiol, it was concluded that the interaction between the hydroxyl groups of 2-mercaptoethanol might play a significant role in the adsorption step of 2-mercaptoethanol on Au(111) to organize the adsorption structures different from those of ethanthiol.
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