The Mechanism of Photohydrosilylation on Silicon and Porous Silicon Surfaces

摘要

Visible or UV light activates H-terminated Si surfaces because of the presence of a photogenerated hole in a Si-Si back-bond. Enhancing the lifetime of this hole at the surface increases reactivity. On the basis of photodynamics and electron transfer theory, the prevalence of two mechanisms of photoactivation (internal photoemission versus interband photoexcitation followed by electron transfer) are explored. To act as an effective trap, an acceptor state for the excited electron must either be populated directly by photoexcitation or the state must lie in a band gap (or both). It is predicted that oxidants with a properly positioned acceptor level will enhance the reactivity of porous silicon or silicon nanocrystals in a size selective manner.