Dynamics of Laser Ablation and Vaporization of Lead Zirconate Titanate: Target Effects

Abstract

ABSTRACTUsing the pulsed laser deposition (PLD) technique to prepare PbZrxTi(1−x)03 (PZT) films from stoichiometric targets, it has been found that the Pb content of the films is very sensitive to, among other parameters, the phase of the ablation target. In an effort to better understand PZT film growth, a time-of-flight quadrupole mass spectrometer (TOF/QMS) was used to obtain the temporal and mass profiles of material ejected from two different solid targets with a nominal composition of PbZr0.54Ti0.46O3over a laser fluence range of 0.2 to 2.0 J/cm2. The ablation targets were made from either a compressed mixture of oxides or a fully reacted PZT solid. The composition of the plume varied significantly depending upon the phase of the target and the laser fluence. In general, two distinct ejection processes were identified and the TOF profiles observed could be characterized as either thermal vaporization (fluence ≤ 0.3 J/cm2), ablation, with a highly forward directed ejection pattern normal to the target surface, or a combination of the two processes (fluences ≥ 0.3 J/cm2). The thermal vaporization (or low energy) component of the ejected species were modeled using a Maxwell-Boltzmann distribution. The fully reacted target yielded atomic species which had higher translational temperatures (about 100–700K) than the corresponding components of the pressed oxide target. The translational temperatures ranged from about 1000–6500K, depending upon the species and the laser fluence. Both targets showed distinctly different behavior as a function of laser fluence with regard to the production of PbO: the PbO/Pb ratio from the pressed oxide target was roughly constant while the PbO/Pb ratio from the fully reacted target decreased significantly with increased laser fluence. It is postulated that PbO plays an important role in the incorporation of Pb into the film during film growth.