Electrochemically active self-assembled monolayers (SAM) have been successfully fabricated with atomicscale uniformity on a silicon (Si)(1 1 1) surface by immobilizing vinylferrocene (VFC) molecules through Si-C covalent bonds. The reaction of VFC with the hydrogen-terminated Si (H-Si)(1 1 1) surface was photochemically promoted by irradiation of visible light on a H-Si(1 1 1) 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 x 10(-10) mol cm(-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. (C) 2011 Elsevier Inc. All rights reserved.