The role of Pi-conjugation in attachment of organic molecules to the silicon (0 0 1) surface

We have investigated the role of conjugation in attachment of multifunctional organic molecules to the Si(0 0 1) surface. The model molecules we have chosen are acrylonitrile (CH2CHCN) and allyl cyanide (CH2CHCH2CN) due to the electron-withdrawing nature of the cyano group. X-ray photoelectron spectroscopy shows that significant difference in primary binding configuration exists. Infrared spectroscopy establishes that acrylonitrile attaches to the Si(0 0 1) surface primarily through a mechanism involving the cyano group, leading to a novel keteneimine structure that is evidenced by characteristic strong infrared absorbance at 1985 cm−1. Allyl cyanide adsorbs in a way that principally utilizes the vinyl portion of the molecule, leading mainly to alkane infrared absorbance below 3000 cm−1. These results show that conjugation can play an important role in controlling product distribution when attaching multifunctional organic molecules to the Si(0 0 1) surface.