  Synthesis of organic bi-layers on silicon was realized by a combination of
surface functionalization under ultra-high vacuum (UHV) conditions and
solution-based click chemistry. The silicon (001) surface was prepared with a
high degree of perfection in UHV and functionalized via chemoselective
adsorption of ethinyl cyclopropyl cyclooctyne from the gas phase. A second
organic layer was then coupled in acetonitrile via the copper-catalyzed alkyne
azide click reaction. The samples were directly transferred from UHV via the
vapour phase of the solvent into the solution of reactants and back to UHV
without contact to ambient conditions. Each reaction step was monitored by
means of X-ray photoelectron spectroscopy in UHV; the N 1s spectra clearly
indicated the click reaction of the azide group in the two test molecules
employed, i.e., methyl-subsituted benzylazide and azide substituted pyrene. In
both cases, up to 50 - 60 % of the ethinyl cyclopropyl cyclooctyne molecules on
the surface were reacted.
