Photochemical attachment of organic monolayers onto H-terminated Si(111): radical chain propagation observed via STM studies.
Photochemical reactions of terminal alkenes with hydrogen-terminated silicon surfaces are being used by many groups to produce covalently attached organic monolayers with a wide range of terminal functionalities. Despite the considerable activity in this area, the mechanism for these reactions has not been definitively established. Here we present STM and HREELS data on a sequence of partially reacted samples, showing the progress of the reaction. The attachment reaction is found to proceed via formation of irregularly shaped islands that appear to grow by a pseudorandom walk process. These data support a radical chain propagation mechanism previously suggested for this reaction. However, since the photons employed here (447 nm) lack sufficient energy for Si-H bond cleavage, an alternate mechanism for initiating the chain reaction appears to be required.
Eves
Brian J
BJ
Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands.
Sun
Qiao-Yu
QY
Lopinski
Gregory P
GP
Zuilhof
Han
H