Covalent integration of pyrrolyl units with modified monocrystalline silicon surfaces for macroscale and sub-200 nm-scale localized electropolymerization reactions

Macroscale and localized electrochemical growths of polypyrrole deposits have been performed on monocrystalline Si(111) surfaces modified by pyrrole-terminated organic monolayers. The first approach proposed to induce localized electropolymerization reaction consisted of the high dilution of pyrrole-terminated chains with inert decyl chains in order to have a large separation between the attached monomer units. Unfortunately, this method failed to produce polypyrrole features with precision and control of the structure geometry. More successful results were obtained with the electrochemical dip-pen nanolithography (DPN). A pyrrole-coated conducting AFM tip was brought into contact with a pyrrole-terminated silicon surface and a positive bias of +1.0 V was then applied to the surface for a given period of time. Along this lithographic progress, polypyrrole dots with diameters in the range of 75-200 nm and sub-200 nm- wide lines could be electrogenerated.