Abstract

Surface reactions on semiconductors induced by substrate-to-adsorbate electron transfer are important in chemical processing of semiconductors and in photoelectrochemical solar-energy conversion. We have observed this phenomenon for CH₃Br on GaAs(110) by measuring the kinetic energy of CH₃ fragments ejected by electron-transfer- induced dissociation by using the time- of-flight (TOP) technique. The CH₃ fragment energy is independent of wavelength, indicating that the surface-adsorbate complex dictates the energy of the electrons transferring to the adsorbate. Relaxation to this energy of the photoexcited electrons occurs between the initial excitation and the electron-transfer events. Further, we observed that this energy varies for molecules adsorbed on different surface sites because of the differing interaction between surface atoms and adsorbates immediately after electron capture.

© 1993 Optical Society of America