Laser desorption of C-contaminated Pd clusters grown on MgO(100)

The pulsed laser-induced desorption at 532 nm of C-contaminated Pd clusters epitaxially grown on MgO(100) is investigated by Auger 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 which is insensitive to the laser fluence and to the initial cluster height, but which is sensitive to C recontamination. The estimated laser heating (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.