Long Range Order in Si(100) Surfaces Engineered with Porphyrin Nanostructures

Engineering of Si(100) with ordered organic nanostructures represents an advanced method to manufacture hybrid organic/inorganic systems useful for different applications. Well-ordered and densely-packed molecules can be obtained by a self-assembly process that depends on directional inter-molecular interactions such as π-π stacking, electrostatic, dipole-dipole or van der Waals interactions, and other more complex forces. Macrocycles are well known to aggregate both in solution and in thin films as a result of some of the above-mentioned interaction. In our study, Si(100) substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer that binds to the surface using the -SiCl3 group and leaves unreacted a -CH2Cl group. The remaining alkyl chloride functionality at the top of the Si(100) substrate allowed additional covalent functionalization with a porphyrin monolayer that resulted in ordered, surface-confined porphyrin assemblies. X-ray photoelectron spectroscopy gave indication on the porphyrin grafting mode. Atomic force microscopy showed a long range order of these nanostructures. Emission measurements confirmed the porphyrin luminescence.