Formation of uniform ferrocenyl-terminated monolayer covalently bonded to Si using reaction of hydrogen-terminated Si(111) surface with vinylferrocene/n-decane solution by visible-light excitation

Uniform ferrocenyl-terminated monolayer covalently bonded to Si was formed using reaction of H–Si(111) surface with vinylferrocene/n-decane solution by visible-light excitation, and the resulting VFC-SAM on n-type Si showed positive photo-responsivity. [Display omitted] ► Ferrocenyl-terminated monolayer was directly formed on Si by visible-light excitation. ► The uniformity of the resulting VFC-SAM was examined by AFM. ► The resulting VFC-SAM on n-type Si showed positive photo-responsivity. Electrochemically active self-assembled monolayers (SAM) have been successfully fabricated with atomic-scale uniformity on a silicon (Si)(111) surface by immobilizing vinylferrocene (VFC) molecules through Si–C covalent bonds. The reaction of VFC with the hydrogen-terminated Si (H–Si)(111) surface was photochemically promoted by irradiation of visible light on a H–Si(111) substrate immersed in n-decane solution of VFC. We found that aggregation and polymerization of VFC was avoided when n-decane was used as a solvent. Voltammetric quantification revealed that the surface density of ferrocenyl groups was 1.4×10−10molcm−2, i.e., 11% in substitution rate of Si–H bond. VFC-SAMs were then formed by the optimized preparation method on n-type and p-type Si wafers. VFC-SAM on n-type Si showed positive photo-responsivity, while VFC-SAM on p-type Si showed negative photo-responsivity.