Self-Assembled Melamine Monolayer on Cu(111)

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 degrees 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 e 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.