KINETIC-ENERGY RELEASED DISTRIBUTIONS OF IONS DESORBED FROM H2O SI(100) ADSORPTION SYSTEM BY O 1S EXCITATION/

In order to investigate mechanisms of photon stimulated ion desorption (PSID) of H2O-adsorbed Si(100) surface, we have measured ion kinetic energy distributions (IKEDs) of H+ and O+ in the O Is excitation regio n (500-750 eV), using a time-of-flight technique. The observed IKEDs o f desorbing species (H+ and O+) evidently reflect the primary core exc itations. The average kinetic energy spectrum of H+ is roughly similar to the ion desorption yield and shows a resonant peak at 535 eV and a delayed onset at 570 eV. This suggests that the average kinetic energ y is related to the ion desorption yield. The peak at 535 eV suggests that a strongly antibonding (sigma(O-H)) molecular orbital plays an i mportant role in the enhancement of ion desorption. The onset at 570 e V can be explained by multiple-hole states. It was also found that the average kinetic energy of O+ increases with increasing the excitation energy.