Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR‐ and visible laser pulses with particular attention to cluster generation. Neutral and cationic ZnnOm and InnPm particles of various stoichiometry have been produced and investigated by time‐of‐flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium‐rich with In4P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off‐stoichiometric clusters.