Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

Abstract

A comparative experimental study of pulsed laser ablation in vacuum of two\nbinary semiconductors, zinc oxide and indium phosphide, has been performed\nusing IR-and visible laser pulses with particular attention to cluster\ngeneration. Neutral and cationic Zn\\_n O\\_m and In\\_n P\\_m particles of various\nstoichiometry have been produced and investigated by time-of-flight mass\nspectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters\nare mainly stoichiometric in the ablation plume. In contrast, indium phosphide\nclusters are strongly indium-rich with In\\_4 P being a magic cluster. Analysis\nof the plume composition upon laser exposure has revealed congruent\nvaporization of ZnO and a disproportionate loss of phosphorus by the irradiated\nInP surface. Plume expansion conditions under ZnO ablation are shown to be\nfavourable for stoichiometric cluster formation. A delayed vaporization of\nphosphorus under InP ablation has been observed that results in generation of\noff-stoichiometric clusters.\n