Expansion dynamics of the plasma produced by laser ablation of BaTiO3 in a gas environment

The expansion dynamics of the plasma produced by excimer laser ablation of BaTiO3 has been studied by spatially resolved optical emission spectroscopy over a broad gas pressure range (10(-7)-40 mbar), the gas being either reactive (oxygen) or inert (argon). The results obtained in both environments are qualitatively similar and they show that there is a distance-related pressure threshold above which the expansion dynamics differ from that of the free-expansion regime observed in vacuum. Analysis of the results in the framework of the drag model as well as the shock wave model show that the plasma expansion can be well described by the drag model for the initial stages of the expansion, whereas a delayed shock wave model is required for long distances to the target or high gas pressure. (C) 1997 American Institute of Physics.