LASER DESORPTION OF C-CONTAMINATED PD CLUSTERS GROWN ON MGO(100)

The pulsed laser-induced desorption at 532 nm of C-contaminated Pci cl usters epitaxially grown on MgO(100) is investigated by Anger electron spectroscopy. The desorption efficiency is as large as several tenths of monolayers per pulse. The desorption stops after a number of laser pulses before all Pd and C desorb, yielding a stable final state whic h is insensitive to the laser fluence and to the initial cluster heigh t, but which is sensitive to C recontamination. The estimated laser he ating (neglecting the absorption by C) ranges between 62 and 137 K for 1-nm-high clusters. The possible desorption mechanisms are an etching -type reaction (desorption of Pd-C molecules), the mediation of carbon in the absorption of the laser light and/or a photoassisted mechanism . (C) 1998 Elsevier Science B.V. All rights reserved.