Self-Assembled Melamine Monolayer on Cu(111)
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Abstract
The self-assembled structure of melamine
(1,3,5-triazine-2,4,6-triamine)
deposited on Cu(111) was studied under ultra-high-vacuum conditions
using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy
(XPS), and ultraviolet photoemission spectroscopy (UPS). Molecular
packing and conformation were investigated as a function of the annealing
temperature. The molecules deposited at room temperature were found
to be aligned with the molecular plane approximately perpendicular
to the surface. At around 150 °C, the molecules became aligned
in a row-type structure and were all coupled to the Cu(111) surface.
At still higher annealing temperatures, a new two-dimensional (2D)
network was formed via the polymerization of the adsorbed monolayer
of melamine. A multistep model consistent with STM, XPS, and UPS results
is proposed, starting with a self-organized vertically adsorbed melamine
monolayer and ending with the formation of a 2D network lying on Cu(111)
interpreted as a ring-opening polymerization of melamine. The reactive
Cu(111) surface is believed to be one of the keys in this multistep
reaction