Effect of Ar and O2 Atmospheres on the Fundamental Properties of the Plasma Produced by Laser Ablation of Lithium Niobate

The in uence of gas atmospheres (at 1 torr) of different natures, both reactive (O2) and inert (Ar), on the spatial evolution of the electron temperature (Te) and electron density (Ne) of the plasma generated by laser ablation of a LiNbO3 target is evaluated by optical emission spectroscopy techniques. It is found that the behavior of Ne in the plasma produced in vacuum, argon, and oxygen atmospheres exhibit quite different trends as a function of the distance from the target to the substrate, but the behavior of Te is nearly constant. The spatial constancy of Te in all the atmospheres studied is probably related not only to the low laser irradiance used (0.06 GW cm22), but also to a possible collisional decoupling of the heavy species in the central part of the expanding plasma plume where a low pressure region is formed. The fact that Ne is lower in Ar than in O2 indicates the presence of fewer positive ions in the plasma generated in Ar. The impact of this result on the better crystallinity observed in the LiNbO3 Ž lms grown in Ar is also discussed.