Synthesis, Grafting, and Film Formation of Porphyrins on Silicon Surfaces Using Triazenes

The ability to attach electroactive molecules to semiconductor surfaces to yield hybrid molecular/semiconductor systems is essential for studies in the field of molecular electronics. We have synthesized a porphyrin bearing an aryltriazene group and its Zn, Cu, and Co complexes. Two methods have been developed for covalently grafting these porphyrins and metalloporphyrins to Si(100) surfaces by the in situ conversion of aryldiethyltriazenes to aryldiazonium salts using an acid, followed by the spontaneous grafting of the aryldiazonium salts to the hydride-passivated silicon surface. These porphyrin and metalloporphyrin films were characterized by X-ray photoelectron spectroscopy, ellipsometry, scanning electron microscopy and electrochemistry. The thicknesses of the molecular films thus formed can be controlled by the grafting conditions.