UV-induced grafting of alkenes to silicon surfaces: photoemission versus excitons.
The mechanism of photochemical grafting of alkenes to H-terminated silicon has remained poorly understood. Here we demonstrate the importance of a previously unrecognized initiation process, photoelectron ejection (photoemission), as a facile way of initiating photochemical grafting of liquid alkenes to silicon surfaces when using ultraviolet light. A comparison of Si samples with vastly different photocarrier lifetimes showed no difference in the efficiency of alkene grafting. However, differences in the reactivities of different alkenes with different terminal groups that correlate with the electron affinities of these groups were observed. Our results indicate that photoemission is an effective way of initiating grafting because the irreversible nature of photoemission leaves the sample with a net excess of holes that have no corresponding electrons with which to recombine, while in a competing exciton mechanism, the net concentration of holes is limited by recombination processes.
Wang
Xiaoyu
X
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Ruther
Rose E
RE
Streifer
Jeremy A
JA
Hamers
Robert J
RJ