The role of Pi-conjugation in attachment of organic molecules to the silicon (001) surface

We have investigated the role of conjugation in attachment of multifunctional organic molecules to the Si(001) surface. The model molecules we have chosen are acrylonitrile (CH2=CHCdropN) and allyl cyanide (CH2=CHCH(2)CdropN) 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(001) 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(001) surface. (C) 2002 Published by Elsevier Science B.V.